CHAPTER 3 PROJECT DESCRIPTION AND SITE … 3 PROJECT DESCRIPTION AND SITE CONDITION ... This chapter describes Route 44 relocation project. ... A series of lab tests including direct

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CHAPTER 3 PROJECT DESCRIPTION AND SITE CONDITION 3.1 OVERVIEW This chapter describes Route 44 relocation project. General project information is provided along with details related to the subsurface conditions at the site, the characteristics and engineering parameters of the peat and backfill soils, the design and construction of the embankments, excavations, fills, and retaining walls. Section 3.3 provides the original site information prepared by the Massachusetts Highway Department (MHD) and developed by Ernst et al. (1996). Section 3.5 presents the characteristics and engineering parameters of Carver peat and is based on the research presented in our first report by Paikowsky and Elsayed (2003). 3.2 ROUTE 44 RELOCATION PROJECT Section I of Route 44 project starts in the town of Carver in the vicinity of Route 58 and extends approximately 6.3 miles eastward to meet Section II in Kingston near the Plymouth and Kingston town line. The proposed highway is a four lane divided highway with a typical median width of 60 feet. The project includes the construction of eight on/off ramps and reconstruction or realignment of portions of four secondary roadways that intersect the proposed highway. Preliminary plans show that cut sections of up to 40 feet and embankment fills of up to 35 feet are required.

To minimize the embankments’ fill impact on the wetland, eight retaining walls with a cumulative length of approximately 1.5 miles and twelve steepened 1:1 embankments slopes with a cumulatively length of approximately 0.5 miles are required. Many of the walls pass through cranberry bogs and wetland areas underlain by organic soils that are up to 35 feet thick. The walls that pass through cranberry bogs are flanked by an access road 25 feet wide just above the elevation of the bog. Figure 3.1 presents a completed section of the embankment, MSE wall, access road and capped sheet pile. The picture was taken in April 2005 prior to the roadway completion. 3.3 ORIGINAL SITE INFORMATION 3.3.1 Subsurface Investigation and Field Testing The original site information is provided in the Massachusetts Highway Department (MHD) geotechnical report entitled “Geotechnical Report for Relocated Route 44, Section I Carver, Plympton and Kingston” authored by Ernst et al. (1996). Excerpts of the report are provided in Appendix A. The preliminary subsurface investigation for Section I was performed in January and February of 1988 by Guild Drilling Company under a contract with the Massachusetts Highway Department (MHD). A total of 21 drive sample borings and 216 probe soundings into organics were taken along the proposed location of the highway walls and bridges. Figure 3.2 presents the geologic profile of Route 44 section I. It can be observed that peat layers are mainly located around stations 101+00, 117+50, 141+00, 143+50, 156+00 and 384+00. Figures 3.3 to 3.6 contain the boring logs and probe results for these

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investigations. These borings and probes were taken as a portion of the pilot boring program for the entire Route 44 relocation project performed by Pavlo Engineering Company.

Further subsurface information was obtained from a boring program performed from July 1995 to February 1996. Borings, test pits and additional peat probes were taken by Carr Dee Corporation, of Medford Massachusetts, under contract with the MHD. The boring program involved a total of 253 drive sample borings, 22 test pits and 22 additional peat probes at various locations along the proposed route to obtain specific subsurface information. Of the 253 borings, 45 were drilled at proposed bridge locations and 56 additional borings were drilled at proposed wall location. To obtain ground water level information for design of the highway structures, observation wells were installed in 20 of the completed borings. The locations of these borings, wells and test pits around the five instrumented stations are shown on the boring plan of figure 3.7.

All borings were drilled using rotary bits and water jetting to advance the hole, and steel casing was used to maintain borehole stability. The borings taken for the proposed highway were drilled to predetermined highest bottom elevations and extended at least 10 feet into suitable granular material and at least 10 feet below the proposed grade. Wall borings were drilled until bedrock or refusal (120 blows per 12” penetration) was encountered, or to a depth considered adequate by the geotechnical engineer for the design of shallow foundation in medium dense sand. Cores ten feet into bedrock were obtained in 34 out of 253 borings taken.

Eight of the observation wells were installed in the borings for the design of recharge basins. The installed observation wells each have a 15 feet screen length, approximately 10 feet of which is below the existing groundwater table. During the drilling of the boreholes, falling head permeability/infiltration tests were conducted below the invert elevations of the proposed recharge basins by MHD personnel. CPTU and SCPTU Testing were performed by Write Padgett Christopher (WPC) with the plane view of the test locations presented in Appendix B.

MHD personnel were responsible for the layout, field survey, and inspection of each boring. Classification of soil and rock samples was performed visually in the field by the driller. These samples were later reviewed at MHD Research and Material Lab in south Boston and found to be consistent with drillers’ classification.

3.3.2 Laboratory Testing To investigate the engineering properties of the peat found along the proposed route, extensive laboratory study was carried out at the University of Massachusetts Lowell and is described by Paikowsky and Elsayed (2003). Several undisturbed tube (square

inchinch 1010 × ) samples of the peat were obtained from the bog surface downward. Before driving the tube for sampling into the bog, four triangular stiff plastic segments were attached at the lower tip of the tube to serve as retainers and are shown in Figure 3.8. The retainers were aimed to prevent the sample from coming out when the tube was pulled out of the bog. Figure 3.9 shows the procedure used for driving the square samplers into the peat. The obtained peat samples are shown in figure 3.10.

Since the organic soils were found in areas where fill is proposed, a consolidation test with a long term (10,000 hour) load increment at 2.6 ksf was performed to help predict settlements for the case that some of the organics are left in place. The information obtained

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from section II consists of three consolidation tests and two triaxial strength tests (CIU type). Several index tests of water content, organic content, unit weight and PH were performed as well, (see Appendix A).

Twelve consolidation tests and fourteen Triaxial tests were performed at the Geotechnical Engineering Research Laboratory at UMASS Lowell (Paikowsky and Elsayed, 2003). The test results and related engineering properties of the peat at Route 44 are introduced in section 3.4. A series of lab tests including direct shear test, triaxial tests and field tests including CPT and SPT tests on the backfill were also performed to study engineering properties of the sand and are introduced in section 3.5. 3.4 SUBSURFACE CONDITION AND CONSTRUCTION RECOMMENDATION Throughout the project location, the surficial geology is shown as stratified beds and lenses of well sorted fine to coarse sand with some lenses of gravel, silt and clay. Within 500 feet of the Winnetuxet river, the soils are shown however as stratified beds and lenses of fine sand, silt and clay, with few lenses of gravel and medium to coarse sand.

Based on the boring logs and peat probes, soil profiles were drawn along each of the proposed walls. The profiles show that the general soil type and density is relatively consistent throughout the project. A thin veneer of topsoil overlies deep deposits of coarse to fine sand with some gravel or silt and occasional cobbles and boulders. The organic soils immediately below the surface in the cranberry bog and wetland areas consist primarily of fiberous peat, whereas the organic deposits beneath the pond around station 141+00 to station 160+00 (see figure 3.2) consist primarily of muck and amorphous peat. Since the organic deposits present the major obstacles to the construction of the highway, it was determined to excavate all the organic deposits at the embankments’ location and replace with granular backfill using a sheet pile wall as a retaining structure. Detailed information about the site conditions and construction in organic deposits are provided in the MHD geotechnical report presented in Appendix A. 3.5 PEAT CHARACTERISTICS AND ENGINEERING PARAMETERS

Peat is an organic residue formed through the decomposition of plant and animal

body under the aerobic and anaerobic conditions associated with low temperatures and geological effects such as glacial ice. Common names for accumulation of organic soils include bog, fen, moor, muck, and muskeg. Cranberry bogs at Carver Massachusetts are the result of organic deposit accumulation over a lengthy period of time in kettle holes created by glaciers. Carver peat exhibits poor bearing capacity, high compressibility, and long-term deformation under constant loading (creep effect). A series of laboratory tests including permeability, consolidation, triaxial and direct shear tests had been performed on horizontal and vertical samples at the University of Massachusetts, Lowell (Paikowsky and Elsayed, 2003). Table 3.1 summarizes the index properties and engineering parameters of Carver peat.

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3.6 CHARACTERISTICS AND ENGINEERING PARAMETERS OF THE BACKFILL MATERIAL

3.6.1 Overview

Parts of the new highway alignment (Route 44) span across existing cranberry bogs.

At these roadway sections, sheet piling has been placed and the cranberry bogs have been excavated between the sheet piling. After the excavation of the organic material within the bogs (peat), these sections were backfilled with granular material. Since the site was not dewatered during the backfilling operations, it was suspected that these sands would be in a loose, saturated state, making them susceptible to liquefaction. Deep Dynamic Compaction (DDC) and Vibrofloatation-Compaction (VC) were therefore planned for these areas to support the Mechanically Stabilized Earth (MSE) walls to be constructed on the top of the compacted soils carrying the raised highway. To verify the effectiveness of the deep dynamic compaction, Cone Penetration Testing (CPT) was performed before and after the compaction.

The engineering parameters of the backfill material were determined for use in the FEM analysis of the soil-wall interaction. A series of laboratory tests were conducted and cone penetration tests were interpreted in order to determine the engineering parameters of the backfill materials.

Triaxial and direct shear tests were employed to test the strength parameters of the backfill material. PCPT data were also available to explore the soil profiles at the five instrumented stations, to assess the liquefaction properties and to verify the effectiveness of the DDC test to improve the strength of the backfill. 3.6.2 Laboratory Tests Analysis 3.6.2.1 Sieve Analysis

A backfill material sample for the laboratory tests was obtained from a two feet test

pit below surface at station 143+50 (L). A sieve analysis test was performed and the grain size distribution is presented in figure 3.11. From figure 3.11, it can be seen that the fill material consists mainly of sands with some trace of silt, clay and gravels. Based on the liquefaction assessment standard provided by Tsuchida (1970), it can be seen that the backfill material is susceptible to liquefaction by earthquake shaking or other rapid loading. The liquefaction properties are further examined using the PCPT test results.

3.6.2.2 Triaxial Test Results

Three triaxial tests were carried out on samples obtained from different depth using

confining pressures, cσ , of 4.2 psi, 8.3 psi and 12.5 psi without back pressure. The tested samples unit weights were 125pcf, 126pcf and 125.5 pcf as summarized in table 3.2. Figure 3.12 presents the stress-strain relations for the triaxial tests. It can be seen that the maximum deviatoric stress appears before the axial strain is about 7%. The maximum deviatoric stress increases with the increasing of confining pressure. Under the higher confining stresses, the material exhibits a strain-softening behavior. Figure 3.13 presents the Mohr-Column failure

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envelope of the backfill material samples for peak shear conditions (a) and residual state (b). The friction angle is about 38.9° for the peak strength and 29.0° for the residual state. Based on the stress-strain relationship, the initial elastic modulus iE and secant elastic modulus 50E are obtained, where iE is the slope of the stress-strain curve before axial strain is 4%, and

50E is the slope of the stress-strain curve at 50% of peak stress. The failure elastic modulus

failureE is calculated from the stress-strain curve at the peak stress. Table 3.2 summarizes the triaxial test results of the fill.

3.6.2.3 Direct Shear Tests

A series of direct shear tests were performed in order to determine the shear strength

of the fill and the results are summarized in table 3.3. Figure 3.14 presents the stress-strain curves obtained in the tests. It can be seen that before reaching the peak failure, the shear stress increases with the shear displacement. After undergoing the peak failure, the dense sands soften with the shear strain until the stable state. Figure 3.15 presents the fills peak failure friction angle pφ and residual friction angle Rφ values. The peak failure friction angle is in good agreement with that from the triaxial tests. The residual friction angle is larger than the value obtained from the triaxial tests. 3.6.3 Cone Penetration Test (CPT) 3.6.3.1 Overview

The Cone Penetration Test (CPT) is an important tool in the exploration of

cohesionless soils as laboratory testing is generally not feasible due to the difficulty of obtaining undisturbed samples. CPT is useful in profiling, identification, and assessing engineering parameters including angle of shearing resistance and deformation characteristics of cohesionless soils.

A CPT device consists of a cylindrical probe with a cone-shaped tip with different sensors that allow real time continuous measurements of tip and frictional resistance to penetration while the cone is pushed into the ground at a speed of 2 cm/s. The typical CPT probe measures the stress on the tip, the sleeve friction and the pore water pressure. Some cones are equipped with a geophone in order to be able to perform shear wave velocity measurements. The data is normally read by a field computer that displays real-time data and stores it at regular depth intervals. Measurements can be taken at any intervals desired. Figure 3.16 depicts a typical cone penetration test.

There are several configurations of cones that vary mainly in the position of the pore pressure element. These different configurations are presented in figure 3.17. The piezocone can measure the pore pressure by advancing the cone with a pore pressure probe into the subsurface. Following the fill placement, the Piezocone Penetration Test (PCPT) was used to verify the quality and completeness of the backfill material and its strength before and after the compaction. These tests were conducted and performed by Wright Padgett Christopher (WPC) of South Carolina in accordance with ASTM D5778 “Standard Test Method for Performing Electronic Friction Cone and Piezocone Penetration testing of soils”. The tests locations are provided in Appendix B. The PCPT data of the backfill near the five

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instrumented stations of Route 44 at Carver MA were analyzed in order to obtain the backfill profiling and engineering parameters to be used in the FEM analysis of the soil-wall interaction. Additional analyses examining the CPT and Seismic Cone Penetration Testing (SCPT) at the site are presented by Hajduk et al. (2004).

3.6.3.2 Profiling and Soil Identification

Soil identification can be achieved from the magnitude of the cone resistance, and

more specifically from the friction ratio (i.e. the ratio of local side friction to cone resistance) at the same level. A scheme of identification using the Dutch mechanical friction sleeve tip was first formulated by Begemann (1965) and extended by Schmertmann (1969). A comprehensive scheme was formulated by Douglas and Olsen (1981). A simplified working version was formulated by Robertson and Campanella (1983). The profiling and soils identification for the backfill at the five instrumented stations are based on the simplified working version suggested by Robertson and Campanella.

(1) Station 101+00 Figure 3.18 presents the PCPT results for the backfill at station 101+00. Profiling was determined based on Robertson and Campanella (1983). Figure 3.19 shows the soil identification considering the relation of cone resistance and friction ratio. For the backfill at station 101+00, the soil mainly consists of sands with thin layers of silty sand and clayey silt located at the upper layers. The initial water table level in the backfill was at a depth of about 11 feet from the surface. Because DDC was planned to be employed, it is important to determine whether the soils can be improved by deep compaction. Mitchell (1982) identified soils according to grain size distribution and suggested that most granular soils with a fine content (particles sizes< 0.064 mm) lower than 10% can be compacted by vibratory and impact methods. The disadvantage of compaction criteria based on grain size distribution is that soil samples have to be taken. It is preferable to use the results of the penetration tests for assessment of soil compatibility. Massarsch (1991) proposed compaction criteria for homogenous soils based on CPT cone resistance and friction ratio values as shown in figure 3.19. In the case of thin layers of silt and clay, the effectiveness of soil compaction is reduced.

Based on the data prepared in figure 3.19 and using Massarsch’s method, it is shown that the thin layers of silt and clay are not compactable, and the sand layers are compactable. Using figure 3.18 for comparison between the CPT results before and after the DDC tests, it can be seen that the cone resistance and side friction increased at most penetration depths with a relatively even distribution. The friction ratio values along the depth are almost unchanged. The water table level did not change after compaction. From the analysis of the PCPT results, it can be drawn that the DDC tests were effective to improve the strength and deformation characteristics of the granular fill at station 101+00.

(2) Station 117+50 Figure 3.20 presents the PCPT results for the backfill at station 117+50. The backfill consists mainly of sands with a thin layer of silty sand located at a depth of about 15 ft. The ground water table level is located at a depth of about 12 feet from the surface. Figure 3.21 shows the soil identification of the backfill at station 117+50. According to Massarsch’s method (1991), the backfill is compactable. From the PCPT results presented in figure 3.20, following DDC, the cone resistance and local side friction were improved at most depths, and the water table level was lowered. Before the compaction, the water table level was at a depth of 12 ft below the ground surface and after the DDC it was at

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a depth of 16 ft below the ground surface. The water table level was therefore lowered 4 ft by the compaction.

(3) Station 141+00 Figure 3.22 presents the PCPT results for the backfill at station 141+00. From the soil profile provided in figure 3.23, the backfill consists mainly of sands, with thin layers of silt and clay. Using Massarsch’s method (1991), the sand in the backfill is compactable or marginally compactable, and the silt or clay layers are not compactable. Comparison of the PCPT results before and after the DDC tests are shown in figure 3.22, suggesting that the cone resistance and local side friction of the backfill were improved at most depths and their distributions with the depth were more even. Before DDC, the water table level in the backfill was at a depth of about 4.3 feet from the ground surface, and after DDC, the water table level was lowered to the depth of 12 ft from the ground surface.

(4) Station 143+50 Figure 3.24 presents the PCPT results for the backfill at station 143+50. Based on the data presented in figure 3.25 and using the method suggested by Robertson and Campanella (1983), the backfill consists mainly of sand with thin layers of silty sand. Before the DDC tests, the water table level in the backfill was at about 10 feet depth from the ground surface. The water table level was lowered to a depth of 18 ft below the ground surface after the compaction. Using Massarsch’s method (1991), the backfill is totally compactable or marginally compactable. By comparing the PCPT results before and after the DDC tests as shown in figure 3.24, it can be noticed that cone resistance and local side friction of the backfill were improved at most locations by the DDC and their distributions along the depth were more even after the compaction. (5) Station 156+25 Figure 3.26 presents the PCPT results for the backfill at station 156+25. Based on the data presented in figure 3.27 and using the method suggested by Robertson and Campanella (1983), the backfill consists mainly of sand to silty sand with some thin layers of sandy silt or silt. Using the method suggested by Massarsch (1991), most of the silty sand and sandy silt to silt are not compactable. By comparing the PCPT results before and after the DDC compaction, it can be noticed that the cone resistance and local side friction were improved at most locations and their distributions along the depth became more even after the compaction. The water table level in the backfill did not change before and after the deep dynamic compaction and was located at a depth of about 4.2 feet from the ground surface. The water table level did not change in section 156+25 because the sheet pile did not cut off the water flow path from the outside bogs, which supplements the loss of water in the backfill due to the deep dynamic compaction.

By analyzing the PCPT results of the backfill at the five instrumented stations before and after the DDC, the following conclusions can be drawn:

1. According to the method suggested by Robertson and Campanella (1983), the backfill at the five instrumented stations consists mainly of sand to silty sand. At some stations, there were some thin layers of silt or clay.

2. According to the method suggested by Massarsch (1991), most of the backfill at the five instrumented stations consists of compactable or marginally compactable material, especially for those in the upper layers.

3. Based on the analysis of the PCPT data before and after the DDC, it can be concluded that following the compaction, the cone resistance and local side friction of the backfill was improved to depths ranging from 20 ft to 28 ft. The cone resistance was also found to provide quite uniform resistance within this depth. At stations 117+50, 141+00, and 143+50 the water table levels were

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lowered by 4 ft to 8 ft as the water in the backfill had been expelled out by the compression effect induced by the DDC. At some stations 101+00 and 156+25, there was no apparent water table level changes due to the free water flow path between the inside backfill and the outside water in the bogs.

4. It was proved that deep dynamic compaction (DDC) is an effective way to densify the soil hence improve the soil strength and deformation characteristics. The possibility of liquefaction in the backfill granular materials in earthquake was reduced.

5. 3.6.3.3 Relative Density

Relative density is difficult to measure in laboratory test because of the uncertainties

involved with the natural density and the determination of the maximum and minimum densities (ASTM, 1973). The relationship between relative density, rD , and cone resistance,

cq , are based primarily on calibration chamber test. The relationship between relative density, rD , and cone resistance, cq , of a sand is greatly affected by the sand’s compressibility. For a given value of relative density and effective overburden pressure '

0vσ , a sand of high compressibility has a lower cq than a sand of low compressibility. The relationship between relative density and cone resistance suggested by Jamiolkowski et al. (1985) was employed to estimate the relative density of the backfill. These relationships are applicable to relatively uniform, uncemented, clean, predominantly quartz sand. In a thin sand layer, an underestimation of rD may be obtained because the full cone resistance may not be have been developed. Based on Jamiolkowski et al. (1985):

[ ] 5.0'0

10minmax

max log6698v

tr

qee

eeD

σ+−=

−−

= (3.1)

'0, vcq σ ----- expressed in tons/ 2m .

Figures 3.28 to 3.32 present the relative density, RD , and the dynamic shear modulus and constrained modulus of the backfill with depths at the five instrumented stations before and after DDC. It can be observed that after the deep compaction, the relative density values increased significantly, at some depths by close to 100%. After the DDC, the relative density distribution along the depth became more even than prior to the compaction, a testimony to the effectiveness of the deep dynamic compaction. It also can be observed that the deep compaction has a greater effect on the upper layers than on the deeper layers. After the dynamic compaction, the relative density of the backfill in the upper 20 ft layer was increased by 80 to 100%. However, for the backfill at depths of 20 ft below the ground surface and lower, the improvement was less than 80 percent.

3.6.3.4 Strength

There are several possible methods to determine the effective angle of shear

resistance based on the CPT data analysis. One is to use the relationship between the effective shear resistance angle, 'φ , and the relative density, RD , provided by Schmertmann (1978). Another approach is to use the Terzaghi bearing capacity factor for general shear,

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γN , as an intermediate parameter. A correlation between γN and cq is given by Muhs and Weiss (1971): tqN .5.12=γ . This correlation was derived from a large-scale shallow footing test on sand, and it does not consider the overburden pressure. A direct correlation derived from a bearing capacity theory is developed by Mitchell and Durgunoglu (1975) using a soil–cone friction angle equal to 0.5 'φ and a lateral earth pressure coefficient, '

0 sin1 φ−=K , while ignoring the effects of soil compressibility. In highly compressible sands, 'φ may be significantly higher than that derived from the correlation suggested by Mitchell and Durgunoglu. If fR exceeds about 0.5%, the method developed by Mitchell and Durgunoglu is

believed to underestimate 'φ , because it takes no account of the curvature of the strength envelope. At higher confining pressures, 'φ is somewhat lower. The differences between the estimated and actual friction angle increase with the increase in the relative density in the following way (Jamiolkowski et al., 1985):

,35.0<RD 00 to 10 65.035.0 << RD 20 to 30 85.065.0 << RD 30 to 50

RD<85.0 50 to 80 Figures 3.33 to 3.37 present the range in the backfill internal friction angle 'φ , with

depth at the five instrumented stations, before and after the deep dynamic compaction. These results were based on the chart developed by Mitchell and Durgunoglu (1975), using a soil-to-cone friction angle equal to '5.0 φ and a lateral earth pressure coefficient, φ′−= sin10K . It can be noticed that at a lower overburden effective pressure, 'φ is somewhat higher than that calculation at higher overburden effective pressures. After the deep compaction, 'φ at different overburden effective pressure increases some, which prove that DDC is effective to improve granular materials strength. By comparing with table 3.2 and 3.3, it can be noticed that the laboratory measured peak effective shear resistance angle at different confining pressures fits well with the values from the PCPT data analysis.

3.6.3.5 Deformability

Depending on the problems under consideration, it may be necessary to evaluate one

of three moduli: the constrained modulus, M (which is equal to the reciprocal of the oedometer vertical coefficient of volume change, vm ), the Young’s modulus, E, or the shear modulus G. Because stress-strain curves for sands are non-linear, it is necessary to fix a stress range over which the modulus is to be determined.

(1) Constrained Modulus, (M) Correlations between constrained modulus, M, and cone resistance, cq , are commonly expressed as: cM qM .α= (3.2) where Mα is often stated to be in the range 1.5 to 4. Vesic (1970) suggested the relations:

⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛+=

2

10012 R

MDα (3.3)

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Others such as Parkin and Lunne (1982) developed Mα values for NC sand based on pressure chamber tests. In practice, Mα decreases with increasing cq , and Mα increases with increasing stress level. Webb et al. (1982) suggested that M values should be calculated as follows: Clean sands: ( )2.35.2 +⋅= cqM 2mMN (3.4) Clayey sands: ( )6.17.1 +⋅= cqM 2mMN (3.5)

Lunne and Christoffersen (1983) suggested another calibration for M. They proposed conservative values for the initial tangent constrained modulus, 0M , in NC sands and OC sands. Thus the constrained modulus applicable for the stress range '

0vσ to σσ Δ+'0v can be

estimated as:

5.0'

0

'0

0 )2(V

VVMM

σ

σσ Δ+⋅= (3.6)

The constrained modulus for the backfill at the five instrumented stations was estimated based on Vesic’s relations described in equations 3.2 and 3.3.

The variation of the backfill’s constrained modulus (M) with depth at the five instrumented stations (before and after the DDC) are presented in figures 3.28 to 3.32. It can be observed that the constrained modulus (M) varies little with the change in the overburden pressures. The constrained modulus increased substantially following the deep dynamic compaction, typically by 3 to 4 times the values that were at the same depth before the compaction. At stations 101+00, 141+00 and 156+25, the constrained modulus values of the backfill were improved by up to five times by the compaction, and at the stations 117+50 and 143+50 the constrained modulus values of the backfill increased to twice their values before the compaction. It indicated that DDC compaction is an effective way to improve the granular material deformation capacity. Under a given loading condition, the soil with a larger constrained modulus would have a smaller settlement than that with a smaller constrained modulus. Referring to Route 44 conditions, the above relations suggest that the settlements expected to ensue by the embankment construction would decrease as a result of the DDC and the increase in the constrained modulus. It also can be observed that the DDC compaction has a larger effect on the soils in the upper 20 ft compared to the soils at depths of over 20 ft below the surface.

(2) Dynamic (Small Strain) Shear Modulus, (G) Dynamic shear modulus, G, is of great importance in soil dynamics and earthquake engineering. Based on laboratory tests, Robertson and Campanella (1983) provided the correlations between dynamic shear modulus, cone resistance, and vertical effective stress. Rix and Stokoe (1992) developed the following correlations between dynamic shear modulus, cone resistance, and effective overburden pressure:

75.0

'0

0 1634

−

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛×=⎟⎟

⎠

⎞⎜⎜⎝

⎛

v

t

t

qqG

σ (3.7)

The dynamic shear modulus (G) of the backfill with depth at the five instrumented stations before and after the deep dynamic compaction were calculated based on the above relationship and are shown in figures 3.28 to 3.32. Based on the information presented in the figures, a significant increase in the small strain modulus is observed in stations 141+00 and

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156+25 while a smaller increase is observed at the other three locations. At stations 101+00, 117+50, 141+00 and 143+50, the dynamic shear modulus values of the backfill after the compaction were about 1.3 to 2.0 times higher than the values prior to the compaction. At station 156+25, the dynamic shear modulus was almost doubled along the entire depth due to the DDC.

(3) Young’s Modulus, (E) For other than one-dimensional cases, Young’s modulus, E, is used rather than the constrained modulus, M. As with M, E is dependent on the stress level. Based on pressure chamber tests, Robertson and Campanella (1983) suggested correlations for the secant Young modulus at 25% of the failure stress ( 25E ) and at 50% of the failure stress ( 50E ) for uncemented NC quartz sands. For most foundation problems, 25E is relevant, although 50E may be more relevant when considering end-bearing capacities of piles. Robertson and Campanella suggested that except at very low relative density, 25E varies between about 1.5 cq and just over 2 cq . For OC sands, 50E varies between 6 cq and 11 cq (Baldi et. al., 1982).

Another common way to determine the Young’s modulus E, is based on the dynamics shear modulus, G, using the relationship: ( )ν+= 12 00 GE (3.8) For soils, the value of Poisson ratio commonly ranges between 0.2 and 0.5. Using the method suggested by Robertson and Campanella (1983), the 25E of the backfill was found to be around 5100.2 × psf before the compaction and 6102.1 × psf after the compaction. For the sand below the backfill, E was around 5100.3 × psf before the compaction and 5100.4 × psf after the compaction. Based on equation 3.8 and assuming ν equal to 0.25, the Young’s modulus 0E of the backfill was around 5100.4 × psf before the compaction and 6101.2 × psf after the compaction. For the sand below the backfill, E was about 5103.4 × psf before the compaction and 5102.5 × psf after the compaction. It was noticed that the dynamic compaction had much greater effect on the backfill than on the sand below it. Tables 3.4 to 3.7 summarize the engineering parameters of the backfill and deep sand deposits based on the PCPT field tests before and after the deep dynamic compaction. 3.6.4 Summary

Based on the laboratory and PCPT tests on the backfill material at Route 44, the

following conclusions are derived: 1. The backfill at the five instrumented stations of Route 44 at Carver MA consists

mainly of fine to coarse compactable sand. Based on the information provided by the PCPT, at some stations there are also very thin layers of silt or clay.

2. From the triaxial and direct shear tests on the backfill, the measured peak strength parameters are very similar. From the direct shear test, the peak friction angle is 41.0° and the residual friction angle is 36.0°. From the triaxial test, the measured peak and residual friction angles are 38.9° and 29.0° respectively.

3. From the PCPT results, local side friction and pore pressure before and after the DDC were measured and compared. The engineering parameters of the backfill along penetration depths of 8 ft to 25 ft were obtained. It is shown that DDC

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compaction is an effective way for improving the backfill strength and deformation capacities. Following two passes of the deep dynamic compaction (DDC), the relative density Dr of the backfill was improved by 80 to 100 percent and the values of the dynamic shear, constrained and Young’s moduli were twice the values before the compaction.

3.7 ORIGINAL SHEET PILE DESIGN 3.7.1 Assumed Conditions The original sheet pile design was performed by Geosciences Testing And Research, Inc. (GTR) of North Chelmsford, Massachusetts. Section 3.7 is therefore based on the report entitled “Route 44 Relocation Cantilever Sheeting Design Phase 1 and 2 Carver, Massachusetts” by Chernauskas and Paikowsky (2001).

A mechanically stabilized earth (MSE) wall is proposed for the support of the relocated highway in phase 1 and 2 area. In order to build the MSE wall, the existing peat/muck must be excavated and replaced with granular fill. A combination of vibrocompaction and deep dynamic compaction (DDC) is proposed to compact the fill. Steel sheet piling, supported by cantilever methods, will be used to stabilize the highway alignment during the excavation and fill placement procedures. The steel sheet piling will be left in place and capped after the MSE wall is built. It was assumed that vibrocompaction will be used to compact the soil between the sheeting and MSE wall (on both sides) and the area directly under the MSE will be compacted using DDC methods. Steel sheeting (ASTM A572 Grade 50) consisting of PZ22 and PZ27 sections is required along the sheeting alignments. The lengths of the sheeting vary between 25 and 55 feet, depending on the depth to the bottom of the peat, final grade inside and outside the sheeting, water level, distance to the MSE wall, and the height of the MSE wall. 3.7.2 Design Procedures The methodology used to carry out the sheeting design is:

1. Evaluation of the various stages of construction. 2. Review of soil data and geometry along each sheeting alignment at each station.

Development of simplified profiles for cantilever sheeting analyses and identify grade inside and outside sheeting, top of roadway, bottom of peat, water elevation and MSE wall height and distance from sheeting.

3. Evaluation of the surcharge pressures developed on the sheeting from the MSE wall.

4. Use a computer program (Prosheet) to analyze the sheeting for all possible loading design cases.

5. Estimate the deflections of the sheeting and the corresponding settlements behind the sheeting.

Expansion of the above follows: 1. The stages of construction were identified over the course of the project. The

primary stages with regard to the performance of the cantilever sheeting system include:

121

a. Stage I – Install sheeting. b. Stage II – Excavate peat/muck. A minimum excavation of 5 feet was

assumed in cases where peat/muck was not identified. The maximum excavation approached 30 ft in some areas. The depth of excavation was referenced to the grade just outside the sheeting.

c. Stage III – Place loose granular fill to the top of the sheeting. The backfill was assumed to be placed three feet above water level or at the final grade inside and next to the sheeting, whichever was higher. This grade extends from the sheeting to the MSE wall location.

d. Stage IV – Perform Vibrocompaction (within 20 to 25 feet of the sheeting). Prepare final grade after vibrocompaction using conventional compaction methods. This grade was usually 1 to 2 feet lower than the vibrocompaction working grade.

e. Stage V – Build MSE wall. f. Stage VI – Grade road and cap sheeting.

2. Typical profiles along each sheeting alignment were developed from the boring logs, and profiles available in the geotechnical report and the contract documents. The data associated with the stage of construction was compiled as follows:

Stage II – Thickness of peat (depth of excavation). Stage III – Compaction fill height. Stage IV – Final fill height. Stage V – MSE wall height above final inside grade (above stage IV).

3. The surcharge imposed on the sheeting from the construction of the MSE wall was evaluated using Boussinesq’s elastic theory for strip loading. A unit weight for the fill material was assumed to be 120 pounds per cubic foot, strip width of 45 feet, and distance to sheeting of 20 or 25 feet (depending on stationing) were used in the analyses. A Poisson’s ratio of 0.5 was used for calculation.

4. The elevation of the top of the sheeting must start at the final grade inside the sheeting or 3 feet above the water table, whichever is higher. The vibrocompaction working grade was assumed to be at least 3 feet higher than the water level elevation and extends from the sheeting to the MSE wall location. The water level was taken from the levels provided in the Geotechnical report soil profiles. If the water levels vary from those assumed, the lengths and deflections of the sheeting will differ from those determined in these analysis. The water levels encountered during construction will be reviewed if they are different from those assumed in the analyses. The final sheeting lengths are slightly longer than those necessary from the analysis (up to 5 feet longer) to account for sufficient penetration below the bottom of the backfill (i.e. tip of vibroprobe does not extend near the tip of the sheet to minimize disturbance of the passive resistance on the other side).

5. The predicted greatest deflections during excavation occurs in those areas that have 20 feet or more of peat (deflection are typically between 1 and 10 inches). The greatest additional deflections during the construction of the MSE wall occurs in those areas that have 20 feet or more of peat, are within 20 feet of the MSE wall, or have MSE wall heights greater than 20 feet (additional deflections are typically between 1 and 1-1/2 inches).

122

The sheeting may experience deflections of 1 to 3 inches beyond those shown for stage V if construction loads occur close to the sheeting. For this reason, construction equipment, stockpiling, etc., should not be located within 15 feet of the sheeting. The additional deflection of the sheeting after stage V due to bog access road traffic may approach 1 inch, although this is conservative as the loads were assumed to be permanent even though they are temporary.

The influence of the deflection of the sheeting on the settlement under the MSE wall was investigated using empirical relationships developed by Clough and O’Rourke (1990) and Goldberg et al. (1976). For sandy materials, the MSE wall is outside the settlement zone influenced by lateral wall deflection at the permanent sheeting line in all cases. If still clay is assumed, which can be considered as the worst case scenario, the MSE wall between stations 96+50 and 101+50 (only 20 feet from the sheeting) may experience settlement (and possibly differential settlement) of around 1 inch. 3.7.3 Final Design

1) PZ22 and PZ27 or equivalent (Grade 50) sheeting can be used across the site

during excavation, to retain the fill during Vibrocompaction, and in the permanent condition. Sheeting lengths of 25 to 55 feet are necessary. Refer to table 3.8 for the lengths and sizes of the sheeting corresponding to the station locations. The compaction fill height must be added to the outside sheeting elevation (both provided in table 3.9) to obtain the top of the sheeting elevation at each station location. If the top of sheeting elevation varies from that determined from table 3.9, then the analysis should be reviewed.

2) Estimated sheeting deflections of 1 to 1-1/2 inches may occur during construction of the MSE wall. The MSE wall, however, is located outside the settlement zone influenced by lateral wall deflection at the permanent sheeting line (according to Clough and O’Rourke (1990) and Goldberg et al. (1976)). Under the worst conditions, differential settlement of up to 1 inch may occur under the MSE wall, particularly between stations 96+50 and 101+50 left. Although the preliminary calculations indicate that lateral deflections from the sheeting either do not influence the settlement under the MSE wall or are only minimal, the designer should evaluate this issue more thoroughly.

3) Cranes or other construction loads should not be located within 15 feet of the sheeting to limit deflections after the MSE walls are constructed. Estimated additional deflections of 1 to 3 inches may occur if these construction loads are placed close to the sheeting after stage V begins. Deflections of up to 1 inch may occur due to the light bog access road traffic.

4) The performance of the sheeting is critical with regard to the water level. A net change in water level such that it is higher between the sheets than in the bog/wetland can significantly decrease the stability and increase the deflections of the sheeting. This is of particular importance during the permanent condition. If there is a possibility of different water levels inside and outside the sheeting, then measures such as cutting weep holes in the sheeting can be implemented to allow water to pass through.

123

5) The sheeting should be monitored to record deflections during the various stages of construction, particularly in the deep peat and high MSE wall areas. The sheeting should be measured for lateral deflections at each station and half station location. The measurements should be taken according to the following schedule:

a) Before Stage II (zero reading). b) Midway and end of Stage II. c) Midway and end of Stage III. d) End of Stage III. e) Beginning of Stage V, upon 25%, 50%, and 75% completion of the MSE

wall, and after completion of the MSE wall. 6) If the observed deflections at any time exceed the values estimated herein in table

3.8 and 3.10 at each stage, designers (GTR) must be notified in order to evaluate existing conditions and prepare mitigating procedures to limit further deflections. Some methods to reduce the deflections can include:

a) Driving soldier piles adjacent to the sheeting in deep peat areas to increase stiffness.

b) Reduce the working grade. c) Reduce the final grade.

All the analyses are based on available information from the contract documents. The inspection of the field work regarding the compaction and excavation support system (i.e. excavation, installation, and support survey monitoring) will be performed by others. Excavation, installation, and support system monitoring should be coordinated prior to the start of construction to ensure that all activities and phases of the earth support system installation occur as described in our recommendations or in the drawings/project specifications. If conditions or procedures in the field vary from those assumed here, then GTR will need to review and revise its calculations accordingly.

124

Table 3.1 Summary of index properties and engineering parameters of Carver peat

Table 3.2 Summary of the triaxial test results of the backfill soil at route 44

Parameter cσ (psi) tγ (pcf) φ (degree) iE 50E failureE

Sample 1 4.2 125.0 38.9 3000psi 20673 kPa

1100 psi 7580 kPa

300 psi 2067.3 kPa

Sample 2 8.3 126.0 38.9 3000psi 20673 kPa

1088.7 psi 7502 kPa

385.7 psi 2658 kPa

Sample 3 12.5 125.5 38.9 3000psi 20673 kPa

1470 psi 10130 kPa

840 psi 5788.4 kPa

Average N/A 125.5 38.9 3000psi 20673 kPa

1220 psi 8404 kPa

509 psi 3504 kPa

Parameter Model Name/Symbol Units Magnitudes Notes

Soil unit weight below water table

level satγ (lb/ft3) 66.4 Bulk unit weight test

(Elsayed,2003)

Specific gravity GS ---- 1.5 (Elsayed, 2003) Permeability in

Horizontal direction

Kx (ft/day) 3103.3 −× Permeability test (Elsayed, 2003)

Permeability in Vertical direction Ky (ft/day) 0.033 Permeability test

(Elsayed, 2003) Cohesion (constant) Cref (lb/ft2) 41.7 Triaxial Test

(Elsayed, 2003)

Friction angle φ ( )° 12 Triaxial Test (Elsayed, 2003)

Compression index CC ---- 3.4 Oedometer test (Elsayed, 2003)

Swelling index CS ---- 0.47 Oedometer test (Elsayed, 2003)

Secondary compression index αC ---- 0.15 Oedometer test

(Elsayed, 2003)

Water content ϖ (%) 759~950 (Elsayed, 2003)

Liquid limit L.L (%) 590 (Elsayed, 2003)

Plastic limit P.L (%) 390 (Elsayed, 2003)

Initial void ratio eini. ---- 8.0 Consolidation test (Ernst et al., 1996)

125

Table 3.3 Summary of the direct shear test results of the backfill soil

Test Number Test 1 S1

Test 2 S2

Test 3 S3

Test 4 S4

Test 5 S5

Test 6 S6

dγ pcf

kN/m3

--- 86.00 13.54

--- 104.00 16.38

--- 104.00 16.38

--- 96.00 13.91

--- 100.00 14.49

--- 101.00 14.64

Strain Rate mm/min 0.30 0.30 0.30 0.048 0.30 0.048

Normal Stress psi kPa

--- 3.20 22.08

--- 7.10 48.99

--- 9.00

62.10

--- 9.28 64.03

--- 8.55 58.99

--- 19.13 131.99

Shear Stress psi kPa

--- 3.35 23.11

--- 6.94 47.88

--- 7.30

50.37

--- 10.00 69.00

--- 12.10 83.49

--- 14.45 99.71

Void Ratio 0.93 0.71 0.68 0.72 0.66 0.59

⎟⎟⎠

⎞⎜⎜⎝

⎛= −

p

pp σ

τφ 1tan 21.8° 40.7° 43.8° 49.7° 55.2° 43.0°

⎟⎟⎠

⎞⎜⎜⎝

⎛= −

R

RR σ

τφ 1tan 14.6° 31.0° 35.7° 38.6° 51.1° 36.0°

Table 3.4 Summary of the engineering properties of the backfill before deep dynamic compaction (DDC)

Parameter Name/Symbol Units Magnitudes Notes

Relativity density Dr (%) 65 PCPT test before DDC Soil unit weight

below water table level

satγ (lb/ft3) 120 PCPT test before DDC

Permeability in horizontal direction

Kx (ft/day) 3.0 Dissipation test (PCPT) before DDC

Permeability in vertical direction Ky (ft/day) 3.0 Dissipation test (PCPT)

before DDC Dynamic (small

strain) shear modulus

G (lb/ft2) 51060.1 × PCPT test before DDC

Young’s modulus E (lb/ft2) 5100.4 × ( )ν+= 12GE & TC,

Cohesion C (lb/ft2) 0 TC test, DS test

Friction angle φ ( )° 32 PCPT test before DDC

126

Table 3.5 Summary of the engineering properties of the backfill after deep dynamic compaction (DDC)

Parameter Name/Symbol Units Magnitudes Notes

Relativity density Dr (%) 90 PCPT test after DDC Soil unit weight


satγ (lb/ft3) 131 PCPT test after DDC


Kx (ft/day) 2.0 Dissipation test (PCPT) after DDC


after DDC Dynamic (small


G (lb/ft2) 61084.0 × PCPT test after DDC

Young’s modulus E (lb/ft2) 6101.2 × ( )ν+= 12GE & TC,


Friction angle φ ( )° 44 PCPT test after DDC

Table 3.6 Summary of the engineering properties of the deep sand before deep dynamic compaction (DDC)

Parameter Name/Symbol units Magnitudes Notes

Relativity density Dr (%) 65 PCPT test before DDC Soil unit weight


satγ (lb/ft3) 126 PCPT test before DDC


Kx (ft/day) 3.3 Dissipation test (PCPT) before DDC


before DDC Dynamic (small


G (lb/ft2) 51073.1 × PCPT test before DDC

Young’s modulus E (lb/ft2) 51032.4 × ( )ν+= 12GE Cohesion C (lb/ft2) 0 TC test, DS test

Friction angle φ ( )° 37 PCPT test before DDC

127

Table 3.7 Summary of the engineering properties of the deep sand after deep dynamic compaction (DDC)

Parameter Name/Symbol units Magnitudes Notes

Relativity density Dr (%) 70 PCPT test after DDC

Soil unit weight below water table

level satγ (lb/ft3) 128 PCPT test after DDC


Kx (ft/day) 2.2 Dissipation test (PCPT) after DDC


after DDC Dynamic (small


G (lb/ft2) 51007.2 × PCPT test after DDC

Young’s modulus E (lb/ft2) 51019.5 × ( )ν+= 12GE


Friction angle φ ( )° 38 PCPT test after DDC

128

Table 3.8 Route 44 relocation – phase 1 and 2 cantilevered sheeting analysis summary of results (Chernauskas and Paikowsky, 2001)

Station Sheeting Type

Sheeting Length (feet)

Maximum Stress (ksi)

Estimated Deflection

After excavation (inches)

Estimated Additional Deflection during MSE

wall construction (inches)

96+50 to 99+50 L PZ22 25 4 ~0 1/2 99+50 TO 101+50L PZ27 30 16 ~0 1 142+50 to 147+50L PZ27 40 11 1 1 147+50 to 154+00L PZ27 30 11 ~0 ½ 154+00 to 158+00L PZ22 25 2 ~0 06

158+00 to 162+50L PZ22 30 6 ~0 06

99+00 to 103+00 R PZ27 50 14 3-1/2 1-1/2 103+00 to 108+50R PZ22 25 8 ~0 1/2 117+50 to 118+50R PZ27 30 10 ~0 1 136+50 to 138+00R PZ22 20 4 ~0 06

138+00 to 142+50R PZ27 55 22 9-1/2 1 142+50 to 143+50R PZ22 25 9 ~0 ½ 151+50 to 153+50R PZ22 30 11 <1/2 ½ 153+50 to 157+50R PZ27 50 13 3-1/2 06

157+50 to 161+00R PZ22 25 8 ~0 1/2 Notes: 1. All sheeting is ASTM A572 Grade 50 steel. 2. The sheeting length is based on the longest length required from the worst case stage. In addition, the

sheeting lengths are typically a few feet longer than required to ensure that the tip of the sheeting is at least 10 feet below the bottom of the backfill material. The elevation of the top of the sheeting must start at the final grade or 3 feet above the water table, whichever is higher.

3. The maximum stress is the highest stress developed in the sheeting over the course of all stages. 4. Represents the estimated deflection after peat/muck excavation. 5. Represents the estimated additional deflection experienced by the sheeting during the construction of the

MSE wall. The sheeting may experience deflection of 1 to 3 inches beyond those shown if construction loads occur within 15 feet of the sheeting after stage V begin. The additional deflection of the sheeting after stage V due to the bog access road traffic may approach 1 inch.

6. No deflection after MSE wall construction due to grade outside sheeting at the same elevation as final grade inside sheeting.

129

Table 3.9 Route 44 relocation – phase 1 and 2 left summary of sheeting data (Chernauskas and Paikowsky, 2001)

Station Wall Drawing Boring

Grade Outside Sheeting

(feet)

Grade inside

Sheeting (feet)

Leveling Pad EL (feet)

Top of

Road EL

(feet)

Existing Grade (feet)

Water Level (feet)

Bottom of peat

EL (feet)

Stage II thickness of peat (feet)

Stage III compaction fill height

(feet)

Stage IV final fill height (feet)

Stage V Wall height above inside grade (feet)

Distance from MSE wall (feet)

9650 W3 525 PWB6 101.8 106.4 106.8 115.2 98 97 96.8 5 6 5 9 20 9700 W3 526 PWB6 97.5 98.4 95.2 115.6 98 97 92.5 5 4 1 17 20 9750 W3 527 PWB6 96.5 99.3 95.2 116.1 98 97 91.5 5 4 3 17 20 9800 W3 528 WB209 96.2 98.9 94.8 116.5 97 97 91.2 5 5 3 18 20 9850 W3 529 WB209 96.2 98.9 95.3 117 97 97 91.2 5 5 3 18 20 9900 W3 530 WB211 96.1 98.8 94.7 117.4 103 97 91.1 5 5 3 19 20 9950 W3 531 WB211 96.5 100.6 96.5 117.9 103 97 91.5 5 5 4 17 20

10000 W3 532 WB211 102.0 108.4 104.3 118.3 103 97 97 5 7 6 10 20 10050 W3 533 WB211 100.2 107.9 104.3 118.8 103 97 95.2 5 9 8 11 20 10100 W3 534 WB211 95.6 103.8 99.7 119.2 103 97 90.6 5 9 8 15 20 10150 W3 535 PWB8 96.1 106.1 102.0 119.7 100 97 91.1 5 11 10 14 20 14250 W6 617 WB236 104.2 108.7 105.1 117.8 108 105 99.2 5 6 5 9 25 14300 W6 618 WB236 104.7 109.3 105.6 117.5 108 105 94.7 10 6 5 8 25 14350 W6 619 WB239 104.2 108.7 105.1 117.4 105 105 84.2 20 6 5 9 25 14400 W6 621 WB239 105.1 105.1 100.1 117.3 105 105 85.1 20 4 0 12 25 14450 W6 621 WB239 105.1 105.1 100.1 117.3 105 105 85.1 20 4 0 12 25 14500 W6 622 WB242 101.5 101.5 99.6 117.5 104 105 86.5 15 8 0 16 25 14550 W6 623 WB242 101.5 101.5 99.6 117.7 104 105 86.5 15 8 0 16 25 14600 W6 624 WB242 101.5 101.5 99.6 118 104 105 81.5 20 8 0 17 25 14650 W6 625 HB465F 101.0 101.0 99.6 118.3 104 105 91.0 10 8 0 17 25 14700 W6 626 HB465F 101.0 101.0 99.2 118.6 104 105 91.0 10 8 0 18 25 14750 W6 627 PWB17 105.1 106.9 104.2 118.9 107 105 100.1 5 4 2 12 25 14800 W6 628 PWB17 105.1 106.9 103.3 119.2 107 105 100.1 5 4 2 12 25 14850 W6 629 PWB17 107.8 107.8 103.2 119.5 107 105 102.8 5 1 0 12 25 14900 W6 630 WB245 104.2 110.1 105.1 119.8 106 105 94.2 10 7 6 10 25 14950 W6 631 WB245 104.2 110.1 105.1 120.1 106 105 94.2 10 7 6 10 25

130

Table 3.9 Route 44 relocation – phase 1 and 2 left summary of sheeting data (Chernauskas and Paikowsky, 2001) (cont’d)

Station Wall Drawing Boring

Grade Outside Sheeting

(feet)

Grade inside

Sheeting (feet)

Leveling Pad EL (feet)

Top of

Road EL

(feet)

Existing Grade (feet)

Water Level (feet)

Bottom of peat

EL (feet)

Stage II thickness of peat (feet)

Stage III compaction fill height

(feet)

Stage IV final fill height (feet)

Stage V Wall height above inside grade (feet)

Distance from MSE wall (feet)

15000 W6 632 WB245 104.2 110.1 105.5 120.4 106 105 94.2 10 7 6 10 25 15050 W6 633 WB245 104.2 110.1 105.5 120.7 106 105 99.2 5 7 6 11 25 15100 W6 634 WB246 104.1 110.5 105.0 121 106 105 99.1 5 7 6 11 25 15150 W6 635 WB246 104.2 110.1 105.1 121.3 106 105 94.2 10 7 6 12 25 15200 W6 636 WB247 104.2 110.1 105.5 121.6 106 105 94.2 10 7 6 12 25 15250 W6 637 WB247 104.2 110.1 105.1 121.9 106 105 94.2 10 7 6 12 25 15300 W6 638 WB247 103.7 110.1 105.1 122.2 106 105 93.7 10 7 6 12 25 15350 W6 639 PWB19 104.2 110.1 105.1 122.5 106 105 99.2 5 7 6 12 25 15450 W6 641 WB249 110.5 110.5 106.9 123.1 109 108.5 105.5 5 2 0 13 25 15500 W6 642 WB249 109.6 109.6 103.3 123.4 109 108.5 104.6 5 3 0 14 25 15550 W6 643 WB250 108.6 108.6 103.6 123.7 110 108.5 103.6 5 4 0 15 25 15600 W6 644 WB250 108.6 108.6 103.6 124 110 108.5 103.6 5 4 0 15 25 15650 W6 645 WB251 108.6 108.6 103.6 124.6 106 108.5 103.6 5 4 0 16 25 15700 W6 646 WB251 108.6 108.6 103.6 124.6 106 108.5 103.6 5 4 0 16 25 15750 W6 647 WB252 108.6 108.6 103.6 124.9 106 108.5 103.6 5 4 0 16 25 15800 W6 648 WB252 109.1 109.1 103.6 125.2 106 108.5 104.1 5 3 0 16 25 15850 W6 649 WB253 105.5 105.5 103.6 125.5 105 108.5 95.5 10 7 0 20 25 15900 W6 650 WB253 108.2 108.2 103.6 125.8 105 108.5 98.2 10 4 0 18 25 15950 W6 651 WB254 105.5 105.5 103.6 126.1 104 108.5 90.5 15 7 0 21 25 16000 W6 652 WB254 108.6 108.6 103.6 126.4 104 108.5 103.6 5 4 0 18 25 16100 W6 654 PWB21 109.1 109.1 103.6 127 107 108.5 99.1 10 3 0 18 25 16150 W6 655 PWB21 109.1 109.1 103.6 127.4 107 108.5 99.1 10 3 0 18 25 16200 W6 656 WB256 109.5 109.5 104.0 127.6 115 108.5 99.5 10 3 0 18 25 16250 W6 657 WB256 109.5 109.5 104.0 128.4 115 108.5 99.5 10 3 0 19 25

131

Table 3.10 Route 44 relocation – phase 1 and 2 left cantilevered sheeting analysis input and results (Chernauskas and Paikowsky, 2001)

Cases Station Stage Cut/Fill surcharge

Water depth below sheet top

(feet)

Sheeting type

Sheeting length (feet)

Maximum Stress (ksi)

Estimated Deflection (inches)

7A II 25 5 PZ27 46 11.1 3-1/2 7B III 7 5 PZ27 37 10.1 3-1/2 7C IV 5 5 PZ27 20.5 11.2 <1/2 7D V 20’ MSE 5 PZ27 35 5.3 1-1/2 7E

99+00 ~

103+00 (R)

VI 250psf adj. 5 PZ27 39 14.1 4-1/2 8A II 5 4 PZ22 13.5 <0.1 ~0 8B III 7 4 PZ22 20 7.6 1 8C IV 5 4 PZ22 16 2.0 <1/2 8D

103+00 ~

108+50 (R) V 19’MSE 4 PZ22 18 3.5 1/2

9A II 10 5 PZ27 20.5 0.2 ~0 9B III 7 5 PZ27 25 6.9 1 9C IV 5 5 PZ27 19.5 1.1 <1/2 9D V 29’MSE 5 PZ27 25 5.5 1 9E

117+50 ~

118+50 (R)

VI 250 psf adj. 5 PZ27 27.5 9.7 1-1/2 10A II 5 5 PZ22 11 <0.1 ~0 10B III 5 5 PZ22 16 3.8 ½ 10C IV 0 5 PZ22 - - - 10D

136+50 ~

138+00 (R) V 18’MSE 5 PZ22 - - -

11A II 30 6 PZ27 54.5 22.1 9-1/2 11B III 7 6 PZ27 42 12.6 5 11C IV 5 6 PZ27 22.5 1.5 <1/2 11D V 13’MSE 6 PZ27 32 3.9 1 11E

138+00 ~

142+50 (R)

VI 250 psf 6 PZ27 41 11.2 4 12A II 5 6 PZ22 13.5 <0.1 ~0 12B III 7 6 PZ22 21 9.3 1-1/2 12C IV 5 6 PZ22 16.5 2.4 <1/2 12D

142+50 ~

143+50 (R) V 8’MSE 6 PZ22 18 3.4 1/2

13A II 10 9 PZ22 23.5 2.0 <1/2 13B III 7 9 PZ22 23 10.7 2 13C IV 6 9 PZ22 19.5 3.5 ½ 13D

151+50 ~

153+50 (R) V 10’MSE 9 PZ22 21.5 5.8 1

14A II 25 6 PZ27 46 11.1 3-1/2 14B III 7 6 PZ27 38.5 12.6 3-1/2 14C IV 0 6 PZ27 - - - 14D

153+50 ~

157+50 (R) V 17’MSE 6 PZ27 - - -

15A II 10 5 PZ22 18.5 0.3 ~0 15B III 5 5 PZ22 20.5 5.9 1 15C IV 5 5 PZ22 20.5 5.9 1 15D

157+50 ~

161+00 (R) V 17’MSE 5 PZ22 22 8.0 1-1/2

132

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l 4A

A-1

-b*

A-1

-b*A-

3*

P-1

3-45

Wal

l 8

A-2

-4

SECTION II

SECTION I

A-2

-4*

P-1

3-4 8

A-3

*

P-1

3-46

GR

OU

ND

SU

RFA

CE

RO

UTE

44

S UB

SUR

FAC

E PR

OFI

LE

Figu

re 3

.2 G

eolo

gic

prof

ile o

f rou

te 4

4

134

BO

RIN

G L

EN

GEN

D

Dis

tance

bet

wee

n s

tation

s is

100 ft

SPT

#'S

US

Undis

turb

ed S

ample

13

N20

GW

E@

Tim

e of

Bor

ing

Wat

er t

abl e

lev

el

GW

E@

Wel

ls a

nd B

ogs

WO

H W

e ight

of H

amm

e r

WO

R W

eight

of R

ods

PEAT P

RO

BE

s tati

on

11

7+

50

(R)

116+

00

stati

on

10

1+

00

(R)

103+

00

70

60

80

PEAT

PW

B-7

ELEVATION, FT

90

100

110

WB-2

10

WB- 2

13U

D

WB-2

34

W-2

15

120

130

98+

00

140

99+

00

101+

00

100+

00

102+

00

FIN

E T

O C

OARSE S

AN

D

(t o

ele

vation 3

0 f

t)

Exi

stin

g G

round

Sur

face

PEAT

PW

B-9

BO

G D

AM

WB-2

17

WB-2

19

HB-4

56F

PWB-1

0

106+

00

104+

00

105+

00

Top

of Pro

pos

ed W

all

108+

00

107+

00

109+

00

HB-4

59F

WB-2

21

PWB-1

1W

B-2

24

113+

00

111+

00

110+

00

112+

00

114+

00

115+

00

PEAT

HB-4

61F

WB-2

26U

DW

-225

PWB-1

2

118+

00

117+

00

119+

00

Figu

re 3

.3 S

ubsu

rfac

e C

ross

-sec

tion

from

stat

ion

98+0

0 (R

) to

119+

00 (R

) inc

ludi

ng th

e in

stru

men

ted

stat

ion

101+

00 (R

) and

11

7+50

(R)

135

15

8

60

Fine

t o C

oars

e S

and (

to e

lev a

tion 2

0 ft)

PW

B-1

6W

B-2

37

WB-2

34U

DW

B-2

32

Existin

g Gro

und

Surfa

ce110

70

156

80

1477

100

ELEVATION, FT (1ft=0.3048m)

90

76

10919

11

71

16/6

''20

WO

R/2

4''

17

11WO

R/6

0''

WO

H/6

0''

8

11

411

40

7

1725

109/6

''12

48

11

8

23

16

14

PEAT P

RO

BE

WO

R

We i

ght

of Rods

WO

H

We i

ght

of H

am

mer

11

Wate

r ta

ble

lev

el

US U

ndis

turb

ed S

ample

13

GW

E@

Tim

e of Bor

i ng

GW

E@

Wel

ls a

nd B

ogs

WO

H/6

0''

1/6

0''

1/1

8''

1/1

2''

PEAT

12/6

''7/6

''12

14

10

1/1

8''

1

US

2

US

1/1

8''

1/6

''14

1

2

2

22

2

Dis

t ance

betw

e en s

tations

is 1

00 ft

BO

RIN

G L

EN

GEN

D

N

11

13

7

SPT#

'S

922

136+

00

WB-2

30

120

192/6

''10

130

135+

00

Top o

f Pro

pose

d W

all

stati

on

14

1+

00

(R)

PW

B-1

3W

B-2

32

142+

00

139+

00

137+

00

138+

00

140+

00

141+

00

143+

00

144+

00

146+

00

145+

00

147+

00

Figu

re 3

.4 S

ubsu

rfac

e cr

oss-

sect

ion

from

stat

ion

135+

00 (R

) to

147+

00 (R

) inc

ludi

ng th

e in

stru

men

ted

stat

ion

141+

00 (R

)

136

Sta

tio

n 1

43

+5

0(L

)

17

17

18

3

18

19

6/6

' '

WO

H/1

2''

WO

H/1

8''

WO

H/1

8''

23

50

R7

10

1111

WO

H/1

8''

144

WO

H/4

8''

WO

H/6

0''

WO

H/5

4''

56

1/3

6''

WO

H/6

0''

WO

H/6

0''

1/1

2''

2/6

''

26

710

1/6

''

2

11

114311

32

17420W

B-2

35

60

7080

90100

110

120

Wate

r ta

ble

lev

el

Exis

ting

Gro

und S

urf

ac e

N

Wei

ght

of H

amm

erW

OHP

EA

T P R

OBE

GW

E@

Wel

ls a

nd

Bogs

GW

E@

Ti m

e o

f Bor

i ng

20

SPT

#'S

13BO

RIN

G L

EN

GEN

D

Dis

tance

bet

we e

n s

tation

s is

100

ft

FIN

E T

O C

OARSE S

AN

D

(to e

leva

tion

10 f

t)

WB-2

46W

B-2

45

PW

B-1

7H

B-4

65F

WB-2

42

PEAT

WB-2

39

BO

G D

AM

WB

-236

WB

-233

PWB-1

4

Top

of

Propos

ed W

all

ELEVATION, FT (1 ft=0.3048m)

130

152+

00

151+

00

150+

00

149+

00

148+

00

147+

00

146+

00

145+

00

144+

00

143+

00

142+

00

141+

00

140+

00

139+

00

138+

00

Figu

re 3

.5 S

ubsu

rfac

e cr

oss-

sect

ion

from

stat

ion

138+

00 (L

) to

152+

00 (L

) inc

ludi

ng in

stru

men

ted

stat

ion

143+

50 (L

)

137

F ine t

o C

oars

e S

and

(t o

ele

vation 1

8 f

t)

Top o

f Pr

opose

d W

all

ELEVATION, FT

5060

70

80

1288

523

24

798

22

158

19

17

16

Exi

stin

g G

round

Surf

ace

150+

00

90

100

110

2 14

116

120

130

HB-4

66F

149+

00

998

1020

29

19

14

26

PW

B- 1

8

11

5 24

WO

H/ 3

0''

13

WO

H/4

8''

WB-2

57

152+

00

WB-2

70

151+

00

153+

00

26

49

PEAT P

RO

BE

WO

R

Weig

ht

of R

ods

WO

H W

eight

of H

amm

e r

GW

E@

Wells

and B

ogs

GW

E@

Tim

e of

Bor ing

US

Undis

turb

ed S

am

ple

Dis

tance

betw

een s

tations

is 1

00 f

t

SPT#

'S

BO

RIN

G L

EN

GEN

D

N20

13

21

149/6

''613

15

18

13

Wate

r ta

ble

leve

l

20

23

26

stati

on

15

6+

25

(R)

WB-2

62

157+

00

37

15 21

1

10

10

10

1P

PEAT

7PP

2 2P

P

WB-2

61

P

154+

00

155+

00

156+

00

WB-2

64

29

30

30

WB-2

63

4/6

''

15

2

49

41

18P

159+

00

158+

00

Figu

re 3

.6 S

ubsu

rfac

e cr

oss-

sect

ion

from

stat

ion

149+

00 (R

) to

159+

00 (R

) inc

ludi

ng th

e in

stru

men

ted

stat

ion

156+

25 (R

)

138

HB-4

61F

PWB-8

WB-2

11

101+

75

101+

60

WB-2

14

WB

-21

3U

DS

ect

ion

10

1+

00

(R)

BO

G

99+

60

PW

B-7

99+

50

RIG

HTT O

F RO

UTE 4

4

Sect

ion

11

7+

50

(R)

116+

60

W-2

25

WB-2

26U

D

118+

61

PWB-1

2

117+

65

118+

00

0

SC

ALE

IN

FE

ET

400

200

600

1000

800

LEFT

OF

RO

UTE 4

4

157+

00

156+

00

W

Mon

i toring W

ell Typ

e

PW

B

Pilo

t W

all Boring

WB

R

etain

ing W

all C

ontr

ol Boring

HB

H

ighw

ay C

ontr

ol B

oring

142+

06

Sec t

ion

14

1+

00

(R)

WB-2

34U

D

140+

50

BO

G

144+

00

141+

85

WB-2

37

Sect

ion

15

6+

25

(R)

BO

G

157+

00

WB-2

62

WB-2

61

156+

00

WB-2

36

BO

G

WB-2

39

Sect

ion

14

3+

50

(L)

WB-2

51

WB-2

50

Figu

re 3

.7 P

lane

vie

w o

f rou

te 4

4 C

arve

r Mas

sach

uset

ts in

clud

ing

the

inst

rum

ente

d se

ctio

ns a

nd re

late

d bo

rings

139

Figure 3.8 Tube used for peat sampling (Elsayed, 2003)

Figure 3.9 Peat sampling in cranberry bog (Elsayed, 2003)

140

Figure 3.10 Extruded wet peat sample (Elsayed, 2003)

Figure 3.11 Sieve analysis of the backfill material at route 44, Carver MA

100 10 1 0.1 0.01 0.001 0.0001Diameter (mm)

0

10

20

30

40

50

60

70

80

90

100

Per

cent

fine

r by

wei

ght

D60 D30 D10

1 inch 3/8 inch No.4 No.10 No.40 No.100 No.200

Cobble GravelSand

Coarse to medium FineSilt Clay

U.S. standard sieve sizes

Grain size distribution Curve(sand sample from Route 44)

1

2

1 Boundary for Most Liquefiable Soil2 Boundary for Potenially Liquefiable soil (TSUCHIDA, 1970)

141

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.22

Axial Strain (%)

0

3

6

9

12

15

18

21

24

27

30

33

36

39

42

45

Dev

iato

r Stre

ss (p

si) (

1 ps

i = 6

.891

kP

a)

sc = 4.2 psigt = 125 pcf

sc = 8.3 psigt = 126 pcf

sc = 12.5 psigt = 125.5 pcf

Figure 3.12 Stress-strain curve from triaxial tests on the backfill soil at Route 44

in Carver

142

0 5 10 15 20 25 30 35 40 45 50 55 60

s (psi) (1 psi = 6.891 kPa)

0

5

10

15

20

25

30

35

40

t

(psi

) (1

psi =

6.8

91 k

Pa)

sc = 12.5 psigt = 125.5 pcf

sc = 4.2 psigt = 125.0 pcf

Φ = 38.90

sc = 8.3 psigt = 126.0 pcf

(a)

0 5 10 15 20 25 30 35 40 45 50 55 60

s (psi) (1 psi = 6.891 kPa)

0

5

10

15

20

25

30

35

40

t

(psi

) (1

psi =

6.8

91 k

Pa)

sc = 12.5 psigt = 125.5 pcf

sc = 4.2 psigt = 125.0 pcf

Φ = 29.00

sc = 8.3 psigt = 126.0 pcf

(b)

Figure 3.13 Mohr-circle of the triaxial samples at (a) failure and the failure envelope of

the backfill soil, and (b) the residual state and the residual failure envelope of the backfill soil

143

0 0.05 0.1 0.15 0.2 0.25Shear Displacement (inch) (1 inch = 0.0254 m)

0

2

4

6

8

10

12

14

16

Shea

r Stre

ss (p

si) (

1 ps

i = 6

.891

kP

a)

0

0.4

0.8

1.2

1.6

2t/s

0

0.4

0.8

1.2

1.6

2

t/s



-0.004

0

0.004

0.008

0.012

0.016

0.02

Nor

mal

Dis

plac

emen

t (in

ch) (

1 in

ch =

0.0

254

m)

Normal Stress3.20 psi7.10 psi9.00 psi9.28 psi8.55 psi19.13 psi

Figure 3.14 Stress-strain curves of direct shear tests on backfill soil

144

0 4 8 12 16 20Normal Stress (psi) (1 psi = 6.891 kPa)

0

4

8

12

16

20

She

ar S

tress

(psi

) (1

psi =

6.8

91 k

Pa)




0

4

8

12

16

20

She

ar S

tress

(psi

) (1

psi =

6.8

91 k

Pa)

FP=410

FR=360

(a) peak failure (b) residual state Figure 3.15 Relationship between normal stress and shear stress obtained by direct shear

tests of the backfill soil

Figure 3.16 Configuration of a typical cone penetration test (website of Frugo, Inc.)

145

0 50 100 150 200 250 300 350

Cone resistance, qc (tsf)

28

26

24

22

20

18

16

14

12

10

8

6

4

2

0

Dep

th (f

eet)

0 50 100 150 200 250 300 350


0 1 2 3 4 5

Local side friction, fs (tsf)

0 1 2 3 4 5


-0.5 -0.3 -0.1 0.1 0.3 0.5

Pore pressure, u (tsf)

-0.5 -0.3 -0.1 0.1 0.3 0.5


0 1 2 3 4 5

Friction ratio, Rf=fs.100/qc (%)

0 1 2 3 4 5


28

26

24

22

20

18

16

14

12

10

8

6

4

2

0

Dep

th (f

eet)

Sta.101+00

Silty Sands

Sands

Silty SandsClayey Silts

Sands

Silty Sands

Sands

Before DDCAfter DDC

Before DDCAfter DDC

Before DDCAfter DDC

Before DDCAfter DDC

Hydraustatic

1 ft = 0.3048 m1 tsf = 95.7 kPa

Figure 3.17 Various cone configurations (website of Frugo, Inc.)

Figure 3.18 PCPT results including profiling and soil identification for the backfill material at station 101+00, route 44 in Carver, MA

146

0 1 2 3 4 5 6

Friction ratio, Rf (%)

0.1

0.2

0.3

0.40.50.60.70.80.9

2

3

456789

20

30

40

Con

e re

sist

ance

, qc

(MN

/m2 )

0 1 2 3 4 5 6


0.1

0.2

0.3

0.40.50.60.70.80.9

2

3

456789

20

30

40

Con

e re

sist

ance

, qc

(MN

/m2 )

Sands

Silty Sands

Sands Siltsand Silts

Clayey Siltsand Silty Clay

Clay

Peat

Sta.101+00(Soil classification from Robertson and Campanella,1983)

(Soil classification for DDC, Massarsc, 1991)before DDCafter DDCcompactable

marginallycompactable

not compactable

0 50 100 150 200 250


24

22

20

18

16

14

12

10

8

6

4

2

0

Dep

th (f

eet)

0 50 100 150 200 250


0 1 2 3 4 5


0 1 2 3 4 5


-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6


-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6


0 1 2 3 4 5


24

22

20

18

16

14

12

10

8

6

4

2

0

Dep

th (f

eet)

0 1 2 3 4 5 Friction ratio, Rf=fs.100/qc (%)

Sand

Silty Sand

Sand

Sta. 117+50

Initial After DDC

InitialAfter DDC

InitialAfter DDC

InitialAfter DDC

Hydraustatic (before DDC)

Hydraustatic (after DDC)

(before DDC)

(after DDC)

1 ft = 0.3048 m1 tsf = 95.7 kPa

Figure 3.19 Soils identification of the backfill at station 101+00


147


0 1 2 3 4 5 6


0.1

0.2

0.3

0.40.50.60.70.80.9

2

3

456789

20

30

40

Con

e re

sist

ance

, qc

(MN

/m2 )

0 1 2 3 4 5 6


0.1

0.2

0.3

0.40.50.60.70.80.9

2

3

456789

20

30

40

Con

e re

sist

ance

, qc

(MN

/m2 )

Sands

Silty Sands



Clay

Peat

Sta.117+00(Soil Classification from Robertson and Campanella,1983)

(Soil Classification for DDC from Massarch, 1991)

before DDCafter DDC

compactable


not compactable

0 50 100 150 200 250


40

36

32

28

24

20

16

12

8

4

0

Dep

th (f

eet)

0 50 100 150 200 250


0 0.5 1 1.5 2


0 0.5 1 1.5 2


0 0.5 1 1.5 2 2.5 3


0 0.5 1 1.5 2 2.5 3


0 1 2 3 4 5 6 7

Friction ratio, Rf =fs.100/qc (%)

40

36

32

28

24

20

16

12

8

4

0

Dep

th (f

eet)

0 1 2 3 4 5 6 7

Friction ratio, Rf =fs.100/qc (%)

Initial After DDC

InitialAfter DDC

InitialAfter DDC

InitialAfter DDC

Gravelly sand to sand

Clean sand to silty sand

Silty sand to sandy siltClean sand to silty sandSilty sand to sandy silt

Clean sands to

Silty sand

Silty sand to sandy silty

Clay to silty clay

Clean sand to silty sand

Clayey silt to silty clay

Clean sand to sandy silt

Sta. 141+00

Hydraustatic (before DDC)

Hydraustatic (after DDC)

(before DDC)

(after DDC)

1 ft = 0.3048 m1 tsf = 95.7 kPa


148


0 1 2 3 4 5 6 7


0.1

0.2

0.3

0.40.50.60.70.80.9

2

3

456789

20

30

40

Con

e re

sist

ance

, qc

(MN

/m2 )

0 1 2 3 4 5 6 7


0.1

0.2

0.3

0.40.50.60.70.80.9

2

3

456789

20

30

40

Con

e re

sist

ance

, qc

(MN

/m2 )

Sands

Silty Sands



Clay

Peat



before DDCafter DDC

compactable


not compactable

Figure 3.23 Soils identification of the backfill at station 141+00 0 50 100 150 200 250 300


30

28

26

24

22

20

18

16

14

12

10

8

6

4

2

0

Dep

th (f

eet)

0 50 100 150 200 250 300


-0.5 0 0.5 1 1.5 2 2.5


-0.5 0 0.5 1 1.5 2 2.5


-1 -0.6 -0.2 0.2 0.6 1


-0.8 -0.4 0 0.4 0.8


0 0.4 0.8 1.2 1.6 2

Friction ratio, Rf = fs.100/qc

0 0.4 0.8 1.2 1.6 2

Friction ratio, Rf = fs.100/qc

30

28

26

24

22

20

18

16

14

12

10

8

6

4

2

0

Dep

th (f

eet)

Sta. 143+50

Sand

Silty Sand

Sand

Silty Sand

Sand

InitialAfter DDC

InitialAfter DDC Initial

After DDC

InitialAfter DDC

Hydraustatic(before DDC)

Hydraustatic(after DDC)

(before DDC)

(after DDC)

1 ft = 0.3048 m1 tsf = 95.7 kPa

149

0 100 200 300 400


20

18

16

14

12

10

8

6

4

2

0

Dep

th (f

eet)

0 100 200 300 400


0 1 2 3 4


0 1 2 3 4


-0.2 0 0.2 0.4 0.6 0.8 1


-0.2 0 0.2 0.4 0.6 0.8 1


0 2 4 6 8 10

Friction ratio, Rf=fs.100/qc

0 2 4 6 8 10

Friction ratio, Rf=fs.100/qc

20

18

16

14

12

10

8

6

4

2

0

Dep

th (f

eet)

InitialAfter DDC

Initial

After DDC

InitialAfter DDC

InitialAfter DDC

Sta.156+25

Sand

Sand to silty sand

Silty sand to sandy silt

Sandy siltto

clayey silt

Silty sand to sandy silt

Sand to silty sand

Hydraustatic

1 ft = 0.3048 m1 tsf = 95.7 kPa

0 1 2 3 4 5 6 7


0.1

0.2

0.3

0.40.50.60.70.80.9

2

3

456789

20

30

40

Con

e re

sist

ance

, qc

(MN

/m2 )

0 1 2 3 4 5 6 7Friction ratio, Rf (%)

0.1

0.2

0.3

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CHAPTER 4 SHEET PILE INSTRUMENTATION DESIGN 4.1 OVERVIEW

RT. 44 instrumentation project was initiated by the Massachusetts Highway

Department Geotechnical Section in a detailed memo dated June 21, 2001 (see Hourani, 2001). This memo outlined the five sections chosen for instrumentation and depth and number of instruments to be monitored. Conceptual and detailed design of the instrumentation was prepared by Paikowsky et al. (2001) outlining the pressure cell design, calibration methods and shop and field instrumentation installation details.

The locations selected for the instrumentation are described in this chapter along with the type of instrumentation used for the monitoring. The instrumentation design, construction layout and the designation of the individual units are explained in detail. Further chapters provide details regarding the calibration of the individual vibrating wire total pressure cells (Chapter 5), thin film (tactile) sensors (chapter 6) and the installation of the instrumented sheet piles (Chapter 7). 4.2 LOCATION OF THE INSTRUMENTED SECTIONS

The earth pressure monitoring concentrates on the stresses developing along the depth

of the sheet pile wall and the wall’s deformation in the deep peat deposits. Based on the boring logs, SPT and probing test results provided by the MHD (Massachusetts Highway Department) (refer to section 3.3), five sections were chosen by the MHD for instrumentation (Hourani, 2001). These sections are: Station 101+00(R), 117+50 (R), 141+00(R), 143+50(L), and 156+25(R). Using the cross sections presented in figures 3.2 to 3.6, it can be concluded that the deepest peat deposits coincide with the above five sections chosen for the instrumentation installation. Figure 3.7 presents a plan view of the instrumented sections along the road alignment and the location of relevant borings. Figure 4.1 presents the typical road cross-section in the instrumented locations. 4.3 INSTRUMENTATION REQUIREMENTS AND TYPE 4.3.1 Instrumentation Requirements The following summary of requirements is based on Hourani (2001) and was prepared by Paikowsky et al. (2001). (a) Survey

1. Face of MSE wall at 50 feet intervals 2. Top of permanent sheeting walls at 50 feet intervals 3. Five roadway sections

143+50 (L) 101+00 (R) 117+50 (R) 141+00 (R) 156+25 (R)

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(b) Inclinometers Two inclinometers at each roadway section (c) Total Pressure Cells (TPC)

Six (6) total pressure cells at each roadway section at distances 5 ft., 10 ft. and 15 ft. below access road at two locations (inside and outside) of the sheeting.

(d) Monitoring Stages 1. Inclinometers and Pressure Cells

At 10 construction phases ranging from (a) end of excavation to (j) full height of MSE wall construction.

At each location no later than 48 hours after the construction stage or action has been completed.

2. Settlement points Once a week during all stages of sheeting and MSE wall construction.

3. Extension of Observation Period Based upon the performance of the wall readings may be required

beyond the completion of the project. 4.3.2 General Layout

Figure 4.1 describes a typical general cross-section of the instrumented locations

including the MSE wall, sheet pile, inclinometers and pressure cells. Based on the soil conditions and the depth required for the instruments, anticipated pressures and ranges were calculated and chosen.

4.3.3 Selection of Instrumentation

The most desirable feature to be considered in selecting instruments is reliability.

Instruments should be the simplest to get the job done, be durable to withstand the ambient environment, and not be very sensitive to climatic and other extraneous conditions. Other factors to be considered are cost, skills required to process the data, interference to construction, instrument calibration, special access while monitoring, accuracy, and the range of predicted responses compared with the range of the instrument (Li, 1999). Based on the above criteria the following specifics were determined (Paikowsky et al., 2001):

1. As long term monitoring under groundwater conditions is required, the use of vibrating wire equipment is recommended.

2. Rigid load cells are most appropriate to provide stiffness resembling that of the sheeting.

3. Typical total load cells are round and 9 inches in diameter (manufactured by Geokon, Slope Indicator, RocTest) these instruments can not be assembled on the sheeting used in the RT. 44 project without a modification that would alter the sheeting character.

4. A modified rectangular load cell 100 3 200 mm (4 3 8 inch) manufactured by RocTest (type TPC) was chosen.

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4.4 VIBRATING WIRE TOTAL PRESSURE CELLS 4.4.1 General

Earth pressure measuring devices fall into two categories. One is designed to measure

the total stress at a point in an earth mass (Earth Pressure Cell – EPC) and the other is designed to measure the total stress or contact stress against the face of a structural element (Total Pressure Cell – TPC), see figure 4.2. Devices in the latter category are relatively accurate and reliable, provided the device is designed to behave similarly to the way the structure behaves. In addition, the earth pressures on a structure may be reasonably uniform for the structure as a whole, but are usually very not uniform over an area the size of a pressure cell. This condition results in a wide scatter of data that is difficult to interpret. Earth pressure measuring devices designed to measure stress at a point in a soil mass are not considered as accurate and as reliable as devices to measure stress against a structure. The main problem centers on the measuring device and the difference in the stiffness with the surrounding backfill. 4.4.2 Pressure Range Table 4.1 summarizes various approaches to the evaluation of the required pressure ranges estimated when choosing the instrumentation. The vibrating wire TPCs typically manufactured with the ability to withstand a pressure twice the maximum design pressure. The selected ranges are 15 psi (103 kPa) for the shallow load cells and 25 psi (172 kPa) for the deeper instruments. 4.4.3 TPC Specifications Figures 4.3 and 4.4 provide RocTest Inc. specifications of available EPC’s and TPC’s at the time of the instrumentation design. The TPC are hydraulic cells comprised of an oil filled pressure pad connected to a pressure transducer. The model TPC has a cross-sectional modulus rigidity of approximately 3.53107 psi (2.43108 kPa) making it suitable for embedment in concrete where temperature variations are small. The model TPC pressure cells are fitted with either a FPC pneumatic pad, a vibrating wire pressure transducers or an electrical 4 to 20 mA pressure transducers. The TPC model in rectangular shape is designed for the measurement of radial and tangential stresses. The high stiffness of the TPC pressure cells is due to the very narrow cavity with oil built in the cell and the high stiffness of the pad and the backplate. The vibrating wire transducer pressure cells are monitored manually or automatically using the MB-6T readout unit or the SENSLOG data acquisition system. 4.4.4 Instrumentation Modifications Figures 4.5 and 4.6 provide the RocTest construction details of the selected TPC in its standard manufacturing shape modified to the required thickness. In order to obtain maximum rigidity, load cell face flush with the wall and provide protection of the transducers

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and wires, the following design modification were proposed specifically for RT.44 project (Paikowsky et al., 2001).

1. Integrated backplate (3/16" thick), 8 inch × 16 inch. 2. Recessed cell of 0.335 inch thickness to be flush with the sheeting when mounted

through an opening in the sheet pile. 3. Cut an opening in the sheet pile approx. 4 1/8"×8 1/8" to mount the TPC with

1/16" gap around (isolate from axial stresses in the sheeting) to be filled with calking.

4. Reduced pressure range from the typical lowest range (25 psi). 5. Reconfigure the tubing from the sensor area to the transducer. 6. Attach a steel angle 4" × 4" × 1/4" to provide protection for cables and sensor.

Tack welding most places with tapered shoe at the point below the lowest TPC. Figure 4.7 describes the details of the modified cells and figure 4.8 describes a

photograph of the manufactured modified TPC. 4.4.5 Stiffness Evaluation Stress measurements in soils are difficult mostly due to the variation in the measurement conditions introduced by the measuring device. Variation in the stiffness between the zone of measurement to the surrounding areas may introduce increase or decrease in the stresses acting on that area depending if the deformation at the area decreases or increases, respectively. Similarity a protruding or recessed elements will result with similar effects. The modifications of the TPC and its adaptation to the sheet piles as described in the above section were accompanied by a detailed cell and cell/sheet pile stiffness evaluation carried out by Rowles and Paikowsky (2002). This evaluation included hand calculation and finite element analysis and is described in Appendix D with the following major findings:

1. Based on idealized bending of a rectangular plate of constant thickness and simply supported edges, the maximum expected deflection of the pressure cell devices is 0.0118 in at 25 psi.

2. The addition of the pressure cell and back angle at location A or B had very little effect on the stiffness of the typical sheet pile length that was examined.

3. The pressure cell alone was demonstrated to have a similar stiffness as that of the sheet pile system. Correspondingly, the addition of the pressure cells to the sheet pile walls will have negligible effects on local deformations.

4. The above analyses were based on simplifying assumptions that may differ substantially from the actual conditions in many cases. In general, the assumptions that were used probably resulted in larger deformations. The calculated deflections presented in Appendix D are therefore on the safe side compared to the actual deformation that may occur.

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4.5 SINGLE CELL TACTILE PRESSURE SENSOR 4.5.1 Tactile Sensor Technology Tactile sensor technology makes it possible to measure and present the normal stress distribution over an area in real time as demonstrated in figures 4.9 and 4.10. The figures present the normal stress distribution of a rubber bladder pushing sand against a mat sensor 5315#4 in a calibration chamber (described in chapter 6) before loading and after loading to a pressure of 3.5 psi. The 3-D views of the stress distribution are comprised of 2016 sensing points made of 42 rows and 48 columns of intersection of sensing ink. The implementation of the tactile pressure sensor technology to geotechnical applications was first investigated and presented by Paikowsky and Hajduk (1997), with practical application of the technology to geotechnical related problems presented by Paikowsky and Palmer (1999), including modeling foundation and retaining wall experiments and Paikowsky and Rolwes (2002) investigating the effects of grain size on interfacial and interparticle pressure measurements. The TekScan sensors are available in both grid-based and single load cell configurations. The grid based is also available in a wide range of shapes, sizes and spatial resolutions (sensor spacing). Their measuring pressures capabilities range from 0- to 6891 kPa (0 to 1000 psi). Each application requires an optimal match between the dimensional characteristics of the object(s) to be tested and the spatial resolution and pressure range provided by TekScan's sensor technology.

The standard sensor consists of two thin, flexible polyester sheets that have electrically conductive electrodes deposited in varying pattern. In a simplified example as shown in figure 4.11, the inside surface of one sheet forms a row pattern while the inner surface of the other employs a column pattern. The spacing between the rows and columns varies according to the sensor application and can be as small as 0.5 mm.

Before assembly, a patented, thin semi-conductive coating (ink) is applied as an intermediate layer between the electrical contacts (rows and columns). This ink, unique to TekScan sensors, provides the electrical resistance change at each of intersecting points. The electrical resistance decreases with the increased application force.

When the two polyester sheets are placed on top of each other, a grid pattern is formed, creating a sensing location at each intersection. By measuring the changes in current flow at each intersection point, the applied force distribution pattern can be measured and displayed on the computer screen and the information can be graphically plotted as 2-D or 3-D displays as shown in figure 4.9 and 4.10.

In use, the sensor is installed between two mating surface. The TekScan’s matrix-based systems provide an array of force sensitive cells that enable you to measure the pressure distribution between the two surfaces. The 2-D and 3-D views show the location and magnitude of the force exerted on the surface of the sensors at each sensing locations. Force and pressure changes can be observed, measured, recorded, and analyzed throughout the test, providing a powerful engineering tool. There are two kinds of TekScan sensors available, complex sensor such as mat sensor 5315 as shown in figure 4.12, and a simple single load cell as shown in figure 4.13 The implementation of a multi sensor like the mat, requires expansive connections and although has great advantage (e.g. measuring stress distribution) its use encounters difficulties in harsh field environment. The importance of the actual stress distribution over a

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sheet pile wall like RT. 44 is also secondary and hence the use of a single simple tactile cell was investigated. 4.5.2 Single Cell Construction The single cell provides measurement of pressure over a given area and a simple ohmeter can be used for data acquisition as described in chapter 6. The single cell shown in figure 4.13 is flexible, film thin element not suitable for direct field application, especially when considering the process of driving a sheet pile into the ground. A robust construction was therefore developed (Paikowsky, 2002) allowing easy installation while providing protection to the sensing elements. The developed cell is comprised of a rectangular steel plate (8 inches (W) × 20 inches (L)) on which two single cells are mounted as shown in figure 4.14. With a diameter of 1.75 inches each, the center to center distance between the elements is 12 inches. The single elements are attached with non-shrinking glue to the steel plate as shown in figure 4.15(a) and protected against moisture by a rubber coating as shown in figure 4.15(b). A cut at the center of the plate provides passage of the two connectors through the back plate as shown schematically in figure 4.14 and photographed in figure 4.16. The entire unit was capsulated in a thin metal cover and attached to the face of the sheet pile as shown in figure 4.17.

4.6 INCLINOMETER

Inclinometers can be used to monitor horizontal movements within a soil mass or

along a structure. Inclinometer consists of a casing installed in a vertical borehole or in a pipe installed within or attached to the surface of a structure. The inclinometer casing is grouted within the pipe. Normally, the lower end of the casing is anchored in rock and serves as a reference point. Pipe attached to a sheet pile is normally not anchored in rock and the top of the casing or the pipe are referenced to monuments outside the construction area. A probe, which measures the inclination of the casing at depths determined by the observer, is used for monitoring the full length of the casing. The probe is connected to a graduated electrical cable, which is used to lower and raise the sensor in the casing as depicted in figure 4.18. The upper end of the cable is attached to a readout device that records the inclination of the casing from the vertical. Tilt readings and depth measurements are compared with initial data to determine movements that have occurred. Plastic, aluminum, and steel casing of various sizes and shapes have been successfully used with sheet pile cellular structures. Circular casing with guide grooves and square casing are available from US manufacturers. Casing connected to sheet pile sections must be attached so that casing remains undamaged and securely fastened to the sheet pile after the pile has been completely driven to the design depth. From that reason, a pipe attached to the sheet pile is used and the casing is grouted within the pipe following the installation.

4.7 PIEZOMETER

The term piezometer is used to denote an instrument for monitoring pore pressures in

a sealed-off zone of a borehole or fill. Piezometers can be classified into five types,

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depending on the principle used to activate the device and transmit the data to the point of observation. The five types of piezometers include the open standpipe piezometer, the closed hydraulic piezometer, the diaphragm piezometer, the vibrating wire strain gage piezometer, and the semiconductor strain gage piezometer. An open standpipe piezometer has the advantage of simplicity and its use is widespread. These Piezometers were used in stations 101+00 (R) and 117+50 (R). Vibrating wire piezometers were used at the site at various sections and in particular along with the DDC at sections 101+00 (R) and 117+50 (R). Two vibrating wire piezometers had been installed at both sections on August 22, 2003. Cone tip piezometers type 4500 manufactured by Geokon were installed at the tip of standard 3/4” pipe and pushed into the peat as shown in figure 4.19. 4.8 SHEET PILE INSTRUMENTATION DESIGN

Figure 4.20 presents a schematic of the instrumented sheet pile sections. The main

instrumentation at each station consists of one inclinometer casing and two clusters of pressure cells. One cluster of pressure cell was designed to be installed in the inside web of the sheeting and the other on the outside web. As the sheeting profiles have “male” and “female” connections (depending on the station location), the instrumentations were designed for both options as presented in figure 4.20. The inclinometer casing is located in the corner of the sheet pile, made of a 4” diameter schedule 40 pipe secured by iron angles to the sheeting.

Positions DEFJ are along the depth of the outside web of the sheet pile and positions AGBHC are along the inside web. The purpose of this arrangement of the pressure cells is to investigate the possible variation in the pressure measurements due to the location and the way it is being affected by arching or other preferable stress transformation.

The top of the instrumented sheet pile was designed to be two feet above the ground surface. At each instrumented station, three pairs of vibrating wire total pressure cells (TPC) were designed to be instrumented at a distance of 7 feet, 12 feet, and 17 feet from the top of the sheet pile, equivalent to 5 feet, 10 feet and 15 feet depth from the ground surface. A two unit single tactile cells were designed to be instrumented at position G, 9.5 feet from the top of sheet pile (7.5 feet depth from the ground surface). Additional two tactile sensors units were designed to be instrumented at positions J and H, both 14.5 feet from the top of the sheet pile, 12.5 feet depth from the ground surface as shown in figures 4.20 and 4.21. The distance between two adjacent TPCs along the depth is 5 feet. The distance between the TPC and the adjacent tactile sensors is 2.5 feet. The distance between two adjacent tactile sensors is 5 feet. As a preparation for the installation, six cut-outs are performed at positions A, B, C, D, E, and F, which are oversized compared to the pressure pads of the VWTPC. The oversized cut comes to eliminate stress transformation from the sheeting into the pressure cell hence ensuring no contact between the cell pressure pad (see figures 4.7, 4.8) and the sheeting while being flush with the sheeting surface. The tactile sensors were attached on the sheeting surface hence only a 3/4” opening was required to transfer the connectors and allow the electrical cables to be led through the protected chase created by a 4”34”31/4” steel angle as detailed in figures 4.22 and 4.23. The tactile sensors mounting on the sheeting is described in figure 4.24 and the photograph in figure 4.17 showed both cells when installed in the sheet pile (additional photographs are presented in chapter 7).

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4.9 SECTIONS LAYOUT AND INSTRUMENTATION DESIGNATION 4.9.1 Instrumented Section The instrumentation used at each station are summarized in table 4.2 and described below.

(a) Station 101+00 (R) At station 101+00 (R), a total of six TPCs along with six single cell (3 units) tactile

sensors and one inclinometer casing were installed. A piezometer was installed temporarily to monitor the change in the pore pressure during the deep dynamic compaction (DDC).

(b) Station 117+50 (R) There are a total of six TPCs along with six single cell (3 units) tactile sensors and

one inclinometer casing were installed at station 117+50 (R). A piezometer was installed temporarily to monitor the change in the pore pressure during the deep dynamic compaction (DDC).

(c) Station 141+00 (R) At station 141+00 (R), a total of six TPCs along with six single cell (3 units) tactile

sensors and one inclinometer casing were installed for instrumentation. (d) Station 143+50 (L) There are a total of six TPCs and one inclinometer casing were installed for

instrumentation. No single cell tactile sensor was installed for instrumentation at this station. (e) Station 156+25 (R) At this station, a total of six TPCs along with six single cell (3 units) tactile sensors

and one inclinometer casing were installed. 4.9.2 Instrumentation Designation and Location

Table 4.3 presents the serial numbers of the instrumented pressure cells at the five

stations. The relevant locations are identified in figure 4.20. Table 4.4 provides the numbering of each instrument and its position along with the pressure cells’ serial number, calibration range, cable length, instrumented station, and test meter. As shown in figure 4.20, positions A and D are located at 7 feet from the top of the instrumented sheet pile. Positions B and E are at 12 feet from the top of the instrumented sheet pile and positions C and F are at 17 feet from the top of the instrumented sheet pile. 4.10 SUMMARY Based on the geologic conditions, instruments’ reliability, cost and sensitive to the extraneous condition and so on, five stations (stations 101+00 R, 117+50 R, 141+00 R, 143+50 L, and 156+25 R) located in the cranberry bogs with deep peat deposits finally were determined to be instrumented with inclinometers and modified vibrating wire total pressure cells (VW TPC) along with single tactile sensors to monitor the sheet pile and soil body deformation and the total lateral earth pressure developing in the peat respectively during the entire construction period.

At each selected station, it was designed to be instrumented with two clusters of total pressure cells along with two inclinometer casings. One cluster of pressure cells ( three VW

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TPCs along with 4 single tactile sensors) were designed to be instrumented at positions AGBHC on the inside web sheeting and the other cluster of pressure cells (three VW TPCs along with two single tactile sensors) were to be instrumented at positions DEJF on the outside web sheeting (refer to figure 4.20). The top of the instrumented sheet pile was designed to be 2 ft above the ground surface. The VW TPCs were designed to be 5ft, 10ft, 15ft respectively below the ground surface and single tactile sensors were to be 7.5ft and 12.5ft below the ground surface. At each selected station, one inclinometer casing was designed to be attached on the sheeting to monitor the sheet pile deformation and the other one was designed to be installed in the backfill side (15 ft from the embankment) to monitor the soil body deformation induced by the latter embankment construction. Piezometer and standing pipe piezometer were also chosen to monitor the water table level changes.

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Table 4.1 Evaluation of the pressure range for the TPC (Paikowsky et al., 2001)

Cell # 1 2 3 1. Depth from top of peat (ft) 5 10 15 2. Calc. passive stress (ksf) (initial GTR report) 0.32 0.51 0.69

3. Hydrostatic pressure (ksf) including increased water elevation for barges 0.56 0.87 1.19

4. Subtotal of 2 and 3 (ksf) 0.88 1.38 1.88 5. Re-evaluation of pressure cell stress

based on φ=25° (ksf) 0.65 1.29 1.90

6. Re-evaluation of pressure cell stress based on c=250 psf (ksf) 0.65 0.80 0.95

7. Subtotal of 5 and 3 (ksf) 1.21 2.16 3.09 Design range for cells Max. calc. (psi) (rounded) 10 15 25

Cell range to be used (psi) 15 25 25 Note: 1 ksf = 6.94 psi

Table 4.2 Summary of the instruments used at the five monitored stations

Station VW TPC (#)

Tactile (#)

Inclinometer (#) Piezometer Standing Pipe

Piezometer

Sta.101+00(R) 6 3 1 Yes (temporary) Yes

Sta.117+50(R) 6 3 1 Yes (temporary) Yes

Sta.141+00(R) 6 3 1 ---- Yes

Sta.143+50(L) 6 ---- 1 ---- Yes

Sta.156+25(R) 6 3 1 ---- ----

167

Table 4.3 Summary of pressure cells numbering and designation at the five monitored stations

Vibrating Wire Pressure Cell (TPC) # TekScan Tactile Sensor #

Location Location Station

A B C D E F G H J

101+00 R #2370 #2380 #2388 #2367 #2381 #2393 8up/9down 6up/5down 4up/3down



143+50 L #2369 #2376 #2391 #2371 #2377 #2392 N/A N/A N/A


168

VIBRATING WIRE TOTAL PRESSURE CELL TEKSCAN TACTILE SENSORTPC Calibration Cable Section Location Test Tekscan Calibration Section LocationS/N Range Length Section Cell meter Sensor Range Section Cell Comments

78E0# psi ft # position (in Lab) S/N psi # position2365 15 35 156 A GK-403 1 15 117 G UP rubber coating only2366 15 35 117 A RocTest 2 15 117 G DOWN rubber coating only2367 15 35 101 D RocTest 3 15 101 J DOWN rubber coating only2368 15 35 117 D RocTest 4 15 101 J UP rubber coating only2369 15 35 143 A GK-403 5 15 101 H DOWN rubber+complete Alum.2370 15 35 101 A RocTest 6 15 101 H UP rubber+complete Alum.2371 15 35 143 D GK-403 8 15 101 G UP rubber+Alum epoxy2372 15 35 156 D RocTest 9 15 101 G DOWN rubber+Alum epoxy2373 15 35 141 A RocTest 10 15 117 H UP rubber coating+Alum limited area2374 15 35 141 D RocTest 11 15 117 H DOWN rubber coating+Alum limited area2375 25 40 156 B GK-403 14 15 117 J UP rubber coating+Alum limited area2376 15 40 143 B GK-404 15 15 117 J DOWN rubber coating+Alum limited area2377 15 40 143 E GK-405 16 15 156 G UP rubber coating+Alum limited area2378 15 40 141 E GK-406 7 15 156 G DOWN rubber coating+Alum limited area2379 15 40 141 B GK-407 12 15 156 H UP rubber coating+Alum limited area2380 15 40 101 B GK-408 13 15 156 H DOWN rubber coating+Alum limited area2381 15 40 101 E GK-409 17 15 156 J UP rubber coating+Alum limited area2382 15 40 117 B GK-410 8 15 156 J DOWN rubber coating+Alum limited area2383 15 40 156 E RocTest 19 15 141 UP rubber coating+Alum limited area2384 15 40 117 E GK-403 20 15 141 DOWN rubber coating+Alum limited area2385 35 45 156 C RocTest 23 15 141 UP rubber coating+Alum limited area2386 35 45 117 F RocTest 24 15 141 DOWN rubber coating+Alum limited area2387 35 45 141 C RocTest 21 15 141 UP rubber coating+Alum limited area2388 35 45 101 C RocTest 22 15 141 DOWN rubber coating+Alum limited area2389 35 45 117 C RocTest2390 35 45 141 F RocTest2391 35 45 143 C GK-4032392 35 45 143 F GK-4042393 35 45 101 F RocTest2394 35 45 156 F RocTest

Table 4.4 Instrumentation layout and designation at the five stations

169

Figure 4.1 Typical road cross-section in the instrumented locations (Paikowsky et al., 2001)

170

Pressure Cell Pad

Vibrating Wire Pressure Trnasducer

Electrical Cable

Model TPC

Model EPC

Pressure Tubing

Pressure Gage

Model TPC

Pressure Cell Pad

Pressure Transducer Housing

6.35 mm

&27.94 mm

203.2 mm

530.23 mm

101.6 mm

203.2 mm

Schematic Diagram of Model TPC and EPC

PressurePressure Pad

Figure 4.2 Schematic of Model TPC and EPC

171

Figure 4.3 General information of RocTest TPC

172

Figure 4.4 Specifications of RocTest TPC’s and EPC’s

173

Figure 4.5 Details of the selected TPC modified to a thickness of 0.38" (RocTest-first round design)

174

Figure 4.6 Cross section of TPC and capsulated oil film (RocTest)

175

8"

4"

9"

16"

8"

9"

Transducer

Steel Plate

Pressure Cell

Sheet Pile

FRONT VIEW BACK VIEW

Sheet Pile Pressure Pad

Back Plate

Cross-Section View of Pressure Cell and Sheet Pile

0.335"(3/16)"

Figure 4.7 Detailed modifications of the pressure cell and the back plate layout

176

(a) front view of TPC

(b) back view of TPC

Figure 4.8 The configuration view of TPC cell

177

Figure 4.9 3-D view of stress distribution over a mat tactile sensor 5315#4 (manufactured by Tekscan) before loading

00.511.522.533.544.555.566.577.588.59

6

8

10

12

14

16

18

20

22

24

26

28

30

Figure 4.10 3-D view of stress distribution over the contact area of the mat tactile sensor

5315#4 (manufactured by Tekscan) after loading to 24 kPa

kPa

kPa

178

Figure 4.11 The exploded view of TekScan configuration (website of Tekscan, Inc.)

Figure 4.12 The plane view of mat sensor #5315 (website of Tekscan, Inc.)

179

Figure 4.13 Photograph of a single cell tactile pressure sensor

SCALE:PROJECT:01.150

GEOSCIENCES TESTING AND RESEARCH, INC.

DRAWN BY:JCA N/A

DATE:11/01/02

ROUTE 44 INSTRUMENTATION - SHEETING DESIGN

SHEET:8 of 8

20in

12in

A

A

13.5in

0.2in 2in

STEEL PLATE

STEEL PLATE

SLOT*

SECTION A-A* Note : Beveled edges on one side of slot

0.09in

CONNECTION

TACTILE SENSORDIAMETER OF 2in

MOUNTED TEKSCAN/GTR PRESSURE CELL

FRONT VIEWPLATE WITH TEKSCAN CELLS

BACK VIEWPLATE WITH TEKSCAN CELLS

Figure 4.14 The construction of the single cell tactile pressure sensor (Paikowsky et al., 2002)

180

Figure 4.16 Photograph of the back view of the single cell tactile pressure sensor

Figure 4.15 Photograph of single cells (a) attached on the steel plate and (b) coated with protective rubber

181

Figure 4.17 Photograph of the complete single cell tactile pressure sensor

182

Dep

th t

o S

hal

low

est

read

ing a

s per

cab

le m

ark

s

Read cable marks at top of casing

Stickup

Ground Surface orother suitable reference elevation

Detail 1

Detail 1

A+

A-

B- B

Note:Inclinometer probe is about 800 mm longand about 25 mm in diameter

Inclinometer Probe

Piezometer Cable

Portable Readbox

Water Level

Ground Surface

Hollow Steel Pipe

PiezometerFilter Stone

Exp

ecte

d C

han

ge

in L

evel

Figure 4.18 Schematic of Inclinometer Probe

Figure 4.19 Schematic of Piezometer

183

2'' 3''

7''

9''9''

3''

Sta.101+00(R)Sta.141+00(R)

112

optional 0.75inch diameter opening Tactile Cell TYP.

3'' 2''112

7''

9''

3''

9''

Sta.143+50 (L)Sta.117+50 (R)Sta.156+25 (R)

D (TPC)

19.5''

2 FEET

5 FEET

5 FEET

5 FEET

4 inches

8 in

ches

19.5''

2.5

FEET

A (TPC)

E (TPC)

F (TPC)

J (Tekscan)

B (TPC)

C (TPC)

G (Tekscan)

H (Tekscan)

(TPC) A (TPC) D

(TPC) B

(TPC) C

(Tekscan) G

(Tekscan) H

(TPC) E

(TPC) F

(Tekscan) J

Vibrating Wire Total Pressure Cell (TPC)

13.4" 13.4"

Inclinometer Casing

Inside Web

Outside Web

Inside Web

Outside Web

Fla

nge

Fla

nge

Figure 4.20 Schematic of the sheet pile instrumentation layout

184

SCALE: DATE:PROJECT:01.150


DRAWN BY:JCA N/A 10/18/02


SHEETING PREPARATION LAYOUT


SHEET:2 of 8

10ft

15ft

2ft

4in

8in

2in

2.5ft

2.5ft

Cut-out for TPC Typ.

Optional 0.75 inch diameteropening

5ft

Sheet Pile

Figure 4.21 Schematic of sheet pile presentation for instrumentation

(Paikowsky et al., 2002)

185

DRAWN BY: SCALE:PROJECT:

2ft

1. ALL WELDED CONNECTIONS SHALL BE WELDEDTO CONFORM TO SPECIFICATION A-233, E-70 SERIES.

2. ALL WELDING SHALL CONFORM TO THE LATEST EDITION OR ANSI/A WS D1.1.

GENERAL WELD NOTES:

5ft

10ft

15ft

DETAIL 1

DETAIL 2

JCA N/ADATE:

10/18/0201.150


DETAILS FOR INSTRUMENTATION ANGLE PROTECTION


SHEET:4 of 8

1ft

Optional Tekscan8x20x0.1 inch TLC

4" x 4" x 1/4" AngleTransducer

Back Plate

Cables

Cell

DETAIL 1: PRESSURE CELL AND BACK PLATE - PLAN VIEW

1/4"

1/4"

NOTE: Weld 4" every 1 foot along sheet

Sheet Pile

4"

1/4" 4"

DETAIL 2: ANGLE PROTECTION END - FRONT VIEW

Back Plate

4" x 4" x 1/4" AngleNotched to fit over Back Plate

Welded Cover

Back Plate

Cell

Figure 4.22 Details of instrumentation angle protection (Paikowsky et al., 2002)

186

DRAWN BY: SCALE:JCA N/A

DATE:10/18/02

PROJECT:01.150


DETAILS FOR INSTRUMENTATION ANGLE PROTECTION


SHEET:5 of 8

2ft

5ft

10ft

15ft

1ft

DETAIL 3

DETAIL 4

4" x 4" x 1/4" Angle

Transducer

Back Plate

CablesCell

NOTE: See Sheet 3 of 4 for Welding DetailsDETAIL 3: SIDE VIEW ANGLE PROTECTION

Sheet Pile

DETAIL 4: ANGLE PROTECTION END -SIDE VIEW

4" x 4" x 1/4" AngleNotched to fit overBack Plate

Back Plate

Welded Cover

Cell

NOTCHED ANGLE BEFORE WELDING

Figure 4.23 Details of instrumentation angle protection (Paikowsky et al., 2002)

187

SCALE:PROJECT:01.150


DRAWN BY:JCA N/A

DATE:11/01/02


SHEET:7 of 8

FRONT VIEW BACK VIEW

STEEL PLATE

PRESSURE CELL

SHEET PILE

20in

8in

9in

13.5in

0.2in

TEKSCAN/GTR PRESSURE CELL AND BACK PLATE LAYOUT

Figure 4.24 Details of tactile cell mounting over the sheet pile (Paikowsky et al., 2002)

188

189

CHAPTER 5 CALIBRATION OF THE VIBRATING WIRE TOTAL PRESSURE CELLS (TPC) 5.1 GENERAL

The vibrating wire total pressure cells (VW TPC) and earth pressure cells (EPC) are

designed to measure the total stress acting on and in bulk materials. For example, in embankments, mine backfill and mass concrete, or used in measuring the contact pressures on the tunnel linings, foundations, slurry and retaining walls, culverts or other embedded structures. Chapter 4 describes the cells construction and design as part of the sheet pile instrumentation. In all, 30 TPC cells had been calibrated at the geotechnical engineering research laboratory of the University of Massachusetts Lowell for the instrumentation of the sheet pile installed in the peat and monitored in this project. The following sections describe the calibration of the cells prior to their installation in the sheet piles. 5.2 THE TPC CALIBRATION SYSTEM The schematic of the calibration system for the TPC is presented in figure 5.1 and is made up of four major components:

(1) Pressure control system (2) Temperature controlled chamber Pressure chamber (3) Readout system. FlexPanel manufactured by Humboltd Mfg. Co. shown in figure 5.2, was used as a

pressure control system. The panel is used to control and monitor flow of liquids in and out of various testing apparatuses. This equipment is designed to work with a maximum air pressure of 150 psi. By applying air pressure on water in a burette, the water pressure can be applied via a bladder in a pressure chamber to the TPC.

The temperature controlled chamber presented in figure 5.3 was constructed of an insulated sealed small structure (L8ft×H6ft×W4ft) with one air conditioner for temperature reduction. A bypass of the air conditioner control system allowed its continuous operation and the maintenance of a constant temperature as desired. The small structure housed the pressure chamber system, allowing the TPC calibration for different temperatures.

Figure 5.4 presents a cross-sectional view of the pressure chamber used for testing the TPC in peat. This system was initially developed in the Geotechnical Eng. Research Laboratory at UML for testing mat tactile sensors and is described by Palmer (1999). The system includes a water filled rubber bladder in the lower chamber as shown in figure 5.5. The bladder is connected to the pressure control system by a ¼” hose at its bottom, by which the pressure is controlled. A pressure transducer is connected at the bladder connection for direct measurement of the applied pressure. The bladder is then covered with a layer of peat on which the transducers rest. A rigid cover is then applying as a reaction and the view of the closed system is shown in figure 5.6. Upon application of pressure to the bladder, the bladder transmits the pressure via the peat to the pressure pads of the TPC.

Figure 5.7 presents a photograph of the read-out systems. A vibrating wire readout box GK-403 designed to be used with all of Geokon’s vibrating wire sensors was used for reading the TPC output. The GK-403 allows to read and display readings including

190

temperature, and store all the data in the memory that later can be transmitted to a host computer. The readout system also includes the voltmeter (manufactured by Hewlett Packard) with the accuracy of 0.001 mV used for the pressure transducer as shown in figure 5.7. 5.3 CALIBRATION PROCEDURE

The calibration procedure included the following steps: • Step 1: Calibration of the pressure transducer (performed one time before the

tests) and establishing a calibration factor. The calibration was performed using a special pressure device. See Appendix E for results.

• Step2: Connect all the elements together as shown in figure 5.1. • Step 3: Cover the surface of the bladder with a plastic sheet and fill the gap above

the bladder with peat layer about 0.5 inch thick as shown in figure 5.8. • Step 4: Obtain the pressure cells’ initial readings before their installation in the

calibration chamber. • Step 5: Place two TPC attached by the notched wood cover such that the pad is in

the peat. The TPC and the wood are installed in the chamber as shown in figure 5.9.

• Step 6: Install the stiff metal cover over the pressure chamber and tighten the bolts as shown in figures 5.4 and 5.6.

• Step 7: Connect the cables from the pressure cells to the vibrating wire instrumentation readout box.

• Step 8: Close the door of the temperature chamber and operate the air conditioner (if needed) to reduce the temperature to the one required for the testing and achieve stabilized temperature. The TPC were calibrated in temperatures of 40°, 60°, and 80°F.

• Step 9: Apply pressure via the pressure control system and record the readings of the pressure cells using the readout box while continue to record the applied pressure via readings of the pressure transducer using a voltmeter.

• Step 10: Increase gradually the pressure usually by steps of 1 psi to the required peak pressure of 15 or 35 psi (see table 4.3), and then unload the pressure in steps and record the readings.

• Step 11: Record final readings when the pressure decreases back to zero and the readings stabilized.

• Step 12: Close the pressure control system, disconnect the cables and pressure transmission hose, disassemble the pressure chamber and extract the TPC.

• Step 13: Analyze the readings to obtain the calibration factors. It should be noted that the pressure values appeared on the pressure control system

are not the correct pressures acting on the pressure cells. The pressure acting on the TPC cells should be equal to the readings measured by the transducer, which is equal to the pressure appearing on the pressure control system plus the water pressure in the burette. The transducer pressure values were therefore used in the calibration process.

191

5.4 CALIBRATION FACTORS 5.4.1 Overview

During the calibration process, each TPC was loaded and unloaded (to 15 or 35 psi) at

40°F, 60°F, and 80°F. The relationship between the gage readings and the applied pressure acting on them at different temperatures was drawn and analyzed. The results show that the gages respond linearly with the pressure both in loading and unloading. The obtained relations for the different TPC calibrations under constant pressure or temperature were plotted and are presented in appendix E. Overall, the temperature effect on the TPC readings under the constant pressure are minimal. The following section presents in detail the calibrated results for one TPC with a summary presenting the calibration factors for all the TPC provided in tables 5.1 to 5.3. 5.4.2 Presentation of the Calibration Factors

Figure 5.10, 5.11 and 5.12 present the calibration results for TPC cell 78E2371 at

temperatures 40°F, 60°F, and 80°F, respectively. It can be observed that the gage readings at the different temperatures decrease linearly with the increasing of the pressure. The temperature has a small influence on the calibration factors. The following equation is used in the interpretation of the vibrating wire total pressure cells: P = CF × (L1-L0) (8.1) Where: P = calculated pressure, in psi CF = calibration factor, in psi/LU L0, L1 = initial and current reading, in LU Figures 5.13 to 5.15 present the calibration error for TPC cell 78E2371 at temperatures 40°F, 60°F, and 80°F, respectively. The error estimation was calculated by taking the difference between the actual pressure (for the given temperature) and that calibrated pressure using the manufacturer’s calibration factors (from the factory) determined at 70°F (see table 5.1 to 5.3 and Appendix E). This error calculation is expressed as: Error (%) = (P1 – P0)*100 / P1 (8.2) Where: P1 = actual Pressure, in psi P0 = calculated Pressure, in psi This error calculation does not use the developed calibration factor, hence guarantees the maximum possible error with consideration of temperature. Error calculations and graphs for all 30 TPC’s are presented in Appendix E. Based on the error calculations it can be concluded that using the manufacturer’s calibration would result with an error that does not exceed 5% during either loading or unloading. Figures 5.16 to 5.18 present the percent error of the readings when using the calibration factors provided by the factory against the applied pressure. The error estimation was calculated by taking the difference between the TPC reading under a certain pressure (for the given temperature) and that measured during the factory calibration under the same

192

pressure in 70°F. This error calculation guarantees the maximum possible error without consideration of temperature calibration which was used for in developing figures 5.13 to 5.15 and was also used in the interpretation of the actual field measurements. It can be observed that although greater than before, under a wide range of temperatures, the percent error does not exceed ±5% during either loading or unloading. Figure 5.19 presents the affect of temperature on the gage readings for TPC 78E2371. It can be noticed that under the constant loading, the gage readings of the cell changed very little with the changes of temperatures, which supports the aforementioned conclusion that the effect of the calibrated temperature in the examined range is limited and even without its consideration the practical significance for the field measurements is limited.

5.4.3 Summary of Results

Calibration factors were developed based on the data analysis of the relations between

the applied pressure and gage readings under three temperatures for all 30 vibrating wire total pressure cells (TPC). For all TPCs, the gage readings decreased linearly with the increasing in the applied pressure. The temperature effects are limited and the gage readings linearly change with the temperature. The use of the factory calibration factors results with maximum expected errors, commonly less than 5% for all the 30 cells, under different temperatures. Table 4.3 presents the serial numbers for all the VW TPC including their cable length, allowable applied pressure range, and readout instrument. All the readings obtained by using GEOKON readout box GK-403, should be multiplied by 1.0156, when compared to the readings obtained using the RocTest box. All the calibration factors for the TPC cells derived from the RocTest readings including those calibrated in the factory. Tables 5.1 to 5.3 present the calibration factors for all the 30 TPC at different temperatures. Appendix E provides all the calibration data, graph and error assessment for all the cells. Based on the measured temperature effects on the TPC, it can be assumed that the calibration factors of the TPC are linearly changing with the temperature. If gage readings of the TPC cells are taken at one temperature, the actual pressure acting on the pressure pad at another temperature can be calculated using interpolated calibration factors for that temperature. The interpretation of the field readings used this observation and applied interpolated calibration factors based on the TPC temperature reading in the field and the calibration factors for the various temperatures presented in tables 5.1 to 5.3. Procedure is described in Chapter 8.

193

Table 5.1 Reported and measured TPC calibration factors

Series Number (TPC)

78E 2365

(psi/lu)

78E 2366

(psi/lu)

78E 2367

(psi/lu)

78E 2368

(psi/lu)

78E 2369

(psi/lu)

78E 2370

(psi/lu)

78E 2371

(psi/lu)

78E 2372

(psi/lu)

78E 2373

(psi/lu)

78E 2374

(psi/lu)

Factory -0.02237 -0.02835 -0.02137 -0.02021 -0.01880 -0.02049 -0.01947 -0.02171 -0.02195 -0.02010

40°F -0.02277 -0.02794 -0.02383 -0.02216 -0.01903 -0.01976 -0.01879 -0.02166 -0.02302 -0.01863

60°F -0.02290 -0.02809 -0.02408 -0.02220 -0.01905 -0.01985 -0.01885 -0.02155 -0.02304 -0.01863

80°F -0.02280 -0.02820 -0.02258 -0.02222 -0.01904 -0.01967 -0.01875 -0.02141 -0.02309 -0.01878


Series Number (TPC)

78E 2375

(psi/lu)

78E 2376

(psi/lu)

78E 2377

(psi/lu)

78E 2378

(psi/lu)

78E 2379

(psi/lu)

78E 2380

(psi/lu)

78E 2381

(psi/lu)

78E 2382

(psi/lu)

78E 2383

(psi/lu)

78E 2384

(psi/lu)

Factory -0.02158 -0.02056 -0.02036 -0.02060 -0.02178 -0.02125 -0.02194 -0.02030 -0.01972 -0.02032

40°F -0.02444 -0.02242 -0.02054 -0.02222 -0.02117 -0.02042 -0.02386 -0.01952 -0.02034 -0.02168

60°F -0.02444 -0.02250 -0.02064 -0.02227 -0.02118 -0.02039 -0.02385 -0.01935 -0.02008 -0.02170

80°F -0.02164 -0.02252 -0.02062 -0.02227 -0.02118 -0.02042 -0.02381 -0.01938 -0.02002 -0.02161


Series Number (TPC)

78E 2385

(psi/lu)

78E 2386

(psi/lu)

78E 2387

(psi/lu)

78E 2388

(psi/lu)

78E 2389

(psi/lu)

78E 2390

(psi/lu)

78E 2391

(psi/lu)

78E 2392

(psi/lu)

78E 2393

(psi/lu)

78E 2394

(psi/lu)

Factory -0.02013 -0.02056 -0.02220 -0.02122 -0.01997 -0.02132 -0.02295 -0.02182 -0.02121 -0.02103

40F0 -0.02113 -0.02153 -0.02209 -0.02264 -0.02202 -0.02027 -0.02380 -0.02320 -0.02289 -0.02186

60F0 -0.02076 -0.02151 -0.02201 -0.02264 -0.02201 -0.02045 -0.02378 -0.02323 -0.02304 -0.02176

80F0 -0.02060 -0.02149 -0.02316 -0.02262 -0.02197 -0.02031 -0.02360 -0.02306 -0.02297 -0.02290

194

Water Supply Pressure Control System

Air Pressure Supply

Peat

Deairing System

TPC

Temperature Control System

Bladder

Pressure Transducer

Voltage Readout

Steel Cover Wood Cover

Switch Vibrating Wire Readout Pressure Chamber

Figure 5.1 Schematic of the calibration system

Figure 5.2 Photograph of the FlexPanel used as pressure control system (manufactured by

Humboltd Mfg. Co.)

195

nut

washerfillet welds

19.05 mm (3/4") threaded rod102 mm x 51 mm (4" x 2")aluminum channel

6.4 mm (0.25") thick plate

25.4 nn (1") sq. x 3.2 mm (0.125") w.t. Al. tubing

6.4 mm (0.25")thick plate

6.4 mm (1/4-20) bolt

15.9 mm typ.

6.4 mm (0.25") thick bottom reation plate

38.1 mm (1.5") thick wood table

Steel I-shape supports locatedbelow table surface

15.9 mm (0.625 in.) materialretention frame

masking tape

Pressure bladder

To electro-pneumatic transducer

PeatTPC Wood Cover

Figure 5.3 Photograph of the temperature controlled structure

Figure 5.4 Cross-section of the adopted for the TPC pressure chamber system (modified from

Palmer, 1999)

196

Figure 5.5 Photograph of the pressure bladder in the chamber

Figure 5.6 Photograph of the pressure chamber with the pressure cells

197

Figure 5.7 Photograph of the readout system for the vibrating wire TPC and the voltmeter of the pressure transducer attached to the bladder

Figure 5.8 Photograph of the peat overlaying the bladder in the chamber

198

78E2371 at 40F

Loading: P(psi) = -0.01879*(Li-Lo) + 0.01938R2 = 0.99999

Unloading: P(psi) = -0.01873*(Li-Lo) + 0.07878R2 = 0.99996

Combined: P(psi) = -0.01877*(Li-Lo) + 0.04701R2 = 0.99996

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

-1000.0 -800.0 -600.0 -400.0 -200.0 0.0Li-Lo (LU)

App

lied

Pre

ssur

e (p

si)

loading

unloading

Combined

Linear (loading)

Linear (unloading)

Linear (Combined)

Figure 5.9 Photograph of the TPC embedded in the peat and covered by a wood to accommodate the pressure tubes

Figure 5.10 Gage readings vs. applied pressure for TPC 78E2371 at 40F

199

78E2371 at 60F




0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

-1000.0 -800.0 -600.0 -400.0 -200.0 0.0Li-Lo (LU)

App

lied

Pres

sure

(psi

)

loading

unloading

Combined

Linear (loading)

Linear (unloading)

Linear (Combined)

78E2371 at 80F




0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

-1000.0 -800.0 -600.0 -400.0 -200.0 0.0Li-Lo (LU)

App

lied

Pres

sure

(psi

)

loading

unloading

Combined

Linear (loading)

Linear (unloading)

Linear (Combined)



200

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17Applied Pressure (psi)

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

Erro

r (%

)

0 10 20 30 40 50 60 70 80 90 100 110

Applied Pressure (kPa)

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

Erro

r (%

)

TPC # 78E2371 at 40oFLoadingUnloading


-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

Erro

r (%

)

0 10 20 30 40 50 60 70 80 90 100 110


-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

Erro

r (%

)


Figure 5.13 Calculated error for TPC 78E2371 at 40°F


201


-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

Erro

r (%

)

0 10 20 30 40 50 60 70 80 90 100 110Applied Pressure (kPa)

0

0.5

1

1.5

2

2.5

3

3.5

4

Erro

r (%

)

TPC # 78E2371 at 40F0

Loadingunloading

Figure 5.16 Maximum possible error for TPC 78E2371 at 40F compared to factory calibration


-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

Erro

r (%

)

0 10 20 30 40 50 60 70 80 90 100 110


-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

Erro

r (%

)



202


-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

Erro

r (%

)


0

0.5

1

1.5

2

2.5

3

3.5

4

Err

or (%

)

TPC # 78E2371 at 60F0

Loadingunloading


-5-4.5

-4-3.5

-3-2.5

-2-1.5

-1-0.5

00.5

11.5

22.5

33.5

4

Err

or (%

)


0

0.5

1

1.5

2

2.5

3

3.5

4

Err

or (%

)

TPC # 78E2371 at 80F0

Loadingunloading



203

35 40 45 50 55 60 65 70 75 80 85Temperature (Fo)

3200

3300

3400

3500

3600

3700

3800

3900

4000

4100

4200TP

C R

eadi

ngs

(LU

) Temperature Effect(TPC # 78E2371)

2.5 psi5.0 psi7.5 psi10.0 psi12.5 psi15.0 psi

Figure 5.19 Temperature effect on the gage readings for TPC 78E2371

204

205

CHAPTER 6 CALIBRAION OF THE SINGLE CELL TACTILE PRESSURE SENSORS 6.1 GENERAL Single load cell tactile sensors were developed for experimentation (of the new technology) and implemented for the first time in this project. The construction of the instruments and their layout on the sheet piles are described in Chapter 4. Twelve pressure measurement units were constructed, each made of two single tactile sensor elements. The calibration of these units in the complete load cell arrangement is described in this chapter.

6.2 THE SINGLE CELL TACTILE SENSOR CALIBRATION SYSTEM

The conventional calibration system for TekScan tactile sensors is described by

Paikowsky and Hajduk (1996). The system includes an electronic control pressure application system, a pressure chamber and a data acquisition system. Adaptation of that system to the total pressure cell is presented in Chapter 5. The calibration of the simple tactile single load cells calibration was carried out using the same system as that described in Chapter 5 with the only major difference being the data collection device. A resistance measurement was used directly employing an ohmmeter, manufactured by Hewlett Packard (HP). As only single cell is measured at a time, in line with the TekScan conductive ink and sensor technology, the resistance of the individual cell decreases with an increase in the applied force. Each single load cell was therefore calibrated by individual resistance reading under different pressures and temperatures, examining also creep effects subjecting the sensors to constant load with time. The schematic of the calibration system for the simple single cell tactile pressure sensors is shown in figure 6.1. This system is made up four major components:

(1) Pressure control system (2) Temperature control system (3) Pressure chamber system (4) Readout system

The pressure control system, the pressure transducer readout, the pressure chamber, and the temperature control system used in the calibration of the single load cell tactile sensors are identical to those used for the calibration of the vibrating wire total pressure cells (TPC), which has been presented in section 5.2. 6.3 CALIBRATION PROCEDURES The calibration procedure is similar to the one followed for the TPC cells and described in section 5.3.

• Step 1: Calibration of the pressure transducer (performed one time before the tests) and establishing a calibration factor. The calibration was performed using a special pressure device. See Appendix F for results.

• Step 2: Connect all the elements together as shown in figure 6.1.

206

• Step 3: Cover the surface of the bladder with a plastic sheet and fill the gap above the bladder with about 0.5 inch thick peat layer as shown in figure 5.8.

• Step 4: Obtain the single load cells’ initial readings before their installation in the calibration chamber.

• Step 5: Place two single load cells attached by the notched wood cover such that the pad is in the peat.

• Step 6: Install the stiff metal cover over the pressure chamber and tighten the bolts as shown in figures 5.4 and 5.6.

• Step 7: Connect the cables from the single load cells to the ohmmeter. • Step 8: Close the door of the temperature chamber and operate the air conditioner

(if needed) to reduce the temperature to the one required for the testing and achieve stabilized temperature. The single load cells were calibrated in temperatures of 40°, 60°, and 80°F.

• Step 9: Apply pressure via the pressure control system and record the readings of the individual load cells using ohmmeter while continue to record the applied pressure via readings of the pressure transducer using a voltmeter.

• Step 10: Increase gradually the pressure usually by steps of 1 psi to the required peak pressure of 15, (see table 4.3), and then unload the pressure in steps and record the readings.

• Step 11: Record final readings when the pressure decreases back to zero and the readings stabilized.

• Step 12: Close the pressure control system, disconnect the cables and pressure transmission hose, disassemble the pressure chamber and extract the single load cells.

• Step 13: Analyze the readings to obtain the calibration factors. In order to investigate the effect of creep on the single tactile sensors, they were

calibrated under a constant temperature and pressure over time. For temperature effects, the sensors were calibrated under a constant pressure at different temperatures.

6.4 CALIBRATION RESULTS 6.4.1 Overview

In total, 24 single cell tactile pressure sensors were calibrated with the detailed results

presented in appendix F. The calibration results include for each single load cell the change in resistance with loading, temperature and creep. The readings of the single load cell at different loadings were also summarized in tables. 6.4.2 Presentation of Results

Based on the measurements, analyses and observations of the 24 tested single cell

tactile pressure sensors, it was found that all the tested units had similar reaction under loading and unloading. Figures 6.2 and 6.3 present the resistance measured for cells number 8 and 9 under applied pressure. When not subjected to pressure, the resistance of the cells is infinite, and it decreases with the increasing pressure. The slope of the resistance vs. pressure increases with the pressure. At low pressures, smaller than 4.5 psi, the slope is moderate and

207

is about 0.01 psi/kς. At higher pressure the sensitivity decreases by about 100 times and is approximately 1 psi/kς. It means that at lower pressures large changes in the resistance take place under small pressure increments. At higher pressures, smaller changes of resistance take place under larger pressure increments. The curves describing the relations between pressure and resistance under loading and unloading are almost identical.

Figure 6.4 presents the creep behavior of cells number 8 and 9. Under a constant pressure of 9 psi, the resistance of the cells did not change with time, suggesting that the pressure cells are stable and are not influenced by constant loading over a lengthy period.

Figure 6.5 presents the temperature influence on the resistance of cells number 8 and 9 under a constant pressure. It can be observed that the resistance of the cells increases very little with the increase in the temperature, suggesting that the cells’ resistance is influenced by less than 10% due to temperature changes over a range between 38°F and 83°F. 6.4.3 Calibration Methodology The testing of the single cell tactile pressure sensors lead to the following observations:

1. The cells’ resistance approaches infinity under no load and decreases with pressure increase.

2. The loading and unloading pressure-resistance relations are identical for all practical purposes.

3. The sensors are marginally sensitive to temperature variation and are not sensitive to creep.

4. The sensor’s sensitivity (pressure over resistance) changes dramatically at a given pressure level of about 5 psi, below it the sensitivity is lower compared to that about it with a ratio of about 100.

The two sensitivity levels observed in the sensor’s response can be represented by bi-linear relations of two intersecting lines with different slopes as shown in figure 6.6. For known resistance, the pressure can be calculated using the following relations:

( ) ( ) bkRkpsiKpsiP +Ω×⎟

⎠⎞⎜

⎝⎛

Ω= (6.1)

where: R = cell’s resistance in kς K = slope of line in psi/ kς P = calculated pressure.

The two lines each represent a different slope and a range for which the calculated slope is relevant. For example, following the behavior of sensor #9 as depicted by independent curves in figure 6.7, the following calibration is obtained:

range 0-17.5 kς P (psi) = -2.53R(kς)+40.840 17.5-: kς P (psi) = -0.00923R(kς)+4.817

Figure 6.8 presents the calculated error for tactile single load cell # 9. It was noticed that when the applied pressure is less than 4.50 psi, the error is around 0.5% to 5.5%; when the applied pressure is more than 4.50 psi, the error is around 2% to 3%.

208

6.4.4 Summary of Results The cells’ calibration results are summarized in appendix F. Tables 6.1 summarize the calibration factors for all the single tactile pressure cells

using equation 6.1 and the simplified way described in section 6.4.3. Pressure calculations using this equation are not accurate in every region and are appropriate for the expected pressure range.

209

Table 6.1 Calibration factors for single cell tactile pressure sensors

( ) ( )psibkRkpsiKpsiP +Ω×⎟

⎠⎞⎜

⎝⎛

Ω=)(

Sensor number #1 #2 Calculation Range ( )Ωk (0,15) (15, ∞+ ) (0,15) (15, ∞+ )

Factor K ⎟⎠⎞⎜

⎝⎛

Ωkpsi -1.561 -0.0696 -2.327 -0.038

Intercept b ( )psi 30.904 6.922 34.648 5.477



⎝⎛

Ωkpsi -2.535 -0.062 -4.343 -0.066

Intercept b ( )psi 34.938 5.804 47.000 5.480



⎝⎛

Ωkpsi -2.023 -0.0749 -4.527 -0.204

Intercept b ( )psi 32.111 6.526 50.361 8.433



⎝⎛

Ωkpsi -2.506 -0.0913 -2.000 -0.010

Intercept b ( )psi 33.852 5.735 39.221 -5.017

Sensor number #9 #10 Calculation Range ( )Ωk (0,17.5) (17.5, ∞+ ) (0,22) (22, ∞+ )


⎝⎛

Ωkpsi -2.500 -0.092 -0.804 -0.046

Intercept b ( )psi 40.840 4.817 22.105 5.799

210

Table 6.1 Calibration factors for single cell tactile pressure sensors (cont’d)


⎠⎞⎜

⎝⎛

Ω=)(



⎝⎛

Ωkpsi -0.648 -0.023 -2.483 -0.103

Intercept b ( )psi 16.658 3.771 34.874 7.287



⎝⎛

Ωkpsi -3.078 -0.089 -1.261 -2.261

Intercept b ( )psi 35.581 6.227 27.756 6.895



⎝⎛

Ωkpsi -0.564 -0.009 -1.035 -0.042

Intercept b ( )psi 27.706 4.527 22.73 4.843



⎝⎛

Ωkpsi -1.012 -0.041 -0.616 -0.012

Intercept b ( )psi 22.315 4.755 20.980 3.928



⎝⎛

Ωkpsi -1.699 -0.108 -0.977 -0.018

Intercept b ( )psi 31.500 6.751 26.096 4.591

211

Table 6.1 Calibration factors for single cell tactile pressure sensors (cont’d)


⎠⎞⎜

⎝⎛

Ω=)(



⎝⎛

Ωkpsi -0.913 -0.036 -0.386 -0.007

Intercept b ( )psi 24.367 5.702 26.705 4.467



⎝⎛

Ωkpsi -1.482 -0.080 -1.113 -0.016

Intercept b ( )psi 28.796 6.614 25.505 3.828

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Water Supply Pressure Control System

Air Pressure Supply

Peat

Deairing System

Sensor

Temperature Control System

Bladder

Pressure Transducer

Voltage Readout

Steel Cover Wood Cover

Switch Resistance Readout Pressure Chamber

Figure 6.1 Schematic of the calibration system used for the single tactile pressure sensors

Figure 6.2 Measured resistance vs. applied pressure for cell # 8 at 70F

Resistance (kΩ)

Cell # 8 at 70 F

0

5

10

15

20

25

30

0 50 100 150 200 250 300 350

Pres

sure

(psi

)

Loading (Tekscan 8)

Unloading (Tekscan 8)

213

Cell # 9 at 70 F

0

5

10

15

20

25

30

35

0 50 100 150 200 250 300 350

Pres

sure

(psi

)

Loading (Tekscan 9)

Unloading (Tekscan 9)

Figure 6.3 Measured resistance vs. applied pressure for cell # 9 at 70F

Figure 6.4 Examination of creep for cells number 8 and 9

Constant Pressure 9 psi

15

15.5

16

16.5

17

17.5

18

18.5

19

19.5

20

0 20 40 60 80 100 120 140Time (minute)

TekScan 8

TekScan 9

Res

ista

nce

(kΩ

)

Resistance (kΩ)

214

0 50 100 150 200 250 300 350Resistance (kς )

0

5

10

15

20

25

30

App

lied

Pre

ssur

e (p

si)

0 50 100 150 200 250 300 350Resistance (kς )

0

5

10

15

20

25

30

App

lied

Pre

ssur

e (p

si)

Single Load Cell #9LoadingUnloading

P (psi) = -0.0092 (psi/kς )3 R (kς ) + 4.8168, P < 4.5 psi

P (psi) = -2.50 (psi/kς )3 R (kς ) + 40.84, P > 6.75 psi

Figure 6.5 Examination of temperature effects on the resistance of single load cell s number 8

and 9

Figure 6.6 Example analysis of simplified bilinear calibration for cell # 9

Constant pressure (11.5psi)

9

9.5

10

10.5

11

11.5

12

35 40 45 50 55 60 65 70 75 80 85

Tekscan 8

Tekscan 9

Temperature

Res

ista

nce

215

Figure 6.7 Independent presentation of the simplified bilinear-calibration for cell # 9

Figure 6.8 Calculated error for tactile single load cell # 9 at 70F

0 3 6 9 12 15Resistance (kς )

0

3

6

9

12

15

18

21

24

27

30

App

lied

Pre

ssur

e (p

si)

0 3 6 9 12 15Resistance (kς )

0

3

6

9

12

15

18

21

24

27

30

App

lied

Pre

ssur

e (p

si)

30 60 90 120 150 180 210 240 270 300 330Resistance (kς )

0

1

2

3

4

5

6

7

8

9

10

App

lied

Pre

ssur

e (p

si)

30 60 90 120 150 180 210 240 270 300 330Resistance (kς )

0

1

2

3

4

5

6

7

8

9

10

App

lied

Pre

ssur

e (p

si)

Single Load Cell # 9 at 70Floadingunloading


P (psi) = -2.50 (psi/kς )3 R (kς ) + 40.84

P (psi) = -0.0092 (psi/kς )3 R (kς ) + 4.8168

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5Applied Pressure (psi)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

6

Err

or (%

)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5Applied Pressure (psi)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

6

Err

or (%

)

4.5 9 13.5 18 22.5 27 31.5Applied Pressure (psi)

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

Err

or (%

)

4.5 9 13.5 18 22.5 27 31.5Applied Pressure (psi)

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

Err

or (%

)



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CHAPTER 3 PROJECT DESCRIPTION AND SITE … 3 PROJECT DESCRIPTION AND SITE CONDITION ... This chapter describes Route 44 relocation project. ... A series of lab tests including direct