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UNITED CONSULTING625 Holcomb Bridge Road | Norcross, GA 30071 | (770) 209-0029www.unitedconsulting.com
REPORT Geotechnical Exploration
Murphy Express 5800 West Street and
6200 South Street Salt Lake Valley County
West Valley, Utah
Project Number 2015.0388.01
May 22, 2015
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UNITED CONSULTING
May 22, 2015
Mr. Edward Allen Greenberg Farrow
1430 West Peachtree Street, NW Suite 200 Atlanta, Georgia 30309
Via Email: [email protected]
RE: Report of Geotechnical Exploration Murphy Express
5800 West Street and 6200 South Street West Valley, Salt Lake Valley County, Utah Report No.: 2015.0388.01
Dear Mr. Allen:
United Consulting is pleased to submit this report of our Geotechnical Exploration for the abovereferenced project. We appreciate the opportunity to assist you with this project. Please contact us if you have any questions or ifwe can be of further assistance.
Sincerely,
UNITED CONSULTING
�c� Chris L. Roberds Aaron C. Epstein, P.E.
Senior Geotechnical Engine Utah Registration No. 9356863-
Senior Executive Vice President
Kheibar Khanid okht Project Manager
KK/ ACE/CLR/em
http://ucblade l O/sites/geotechenv/5498/2015.0388.01/Geotechnical Doc11ments/2015.0388. 0 l. UTgeo Murphy oil.doc
625 HOLCOMB BRIDGE ROAD + NORCROSS, GEORGIA 30071 Tel: 770/209-0029 • Fax: 770/582-2900 + Client Services: 800/266-0990 http://www.unitedconsulting.com • E-mail: [email protected]
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TABLE OF CONTENTS
EXECUTIVE SUMMARY PROJECT INFORMATION ............................................................................................................2 PURPOSE ........................................................................................................................................3 SCOPE .............................................................................................................................................3 REGIONAL GEOLOGY .................................................................................................................3 USDA Soil Survey ........................................................................................................................ 4 SUBSURFACE CONDITIONS ......................................................................................................4 LABORATORY TESTING PROGRAM ........................................................................................4 DISCUSSION AND RECOMMENDATIONS ...............................................................................4
Site Preparation ............................................................................................................................5 Difficult Excavation .....................................................................................................................5 Groundwater Considerations ........................................................................................................5 Foundation Design and Construction ...........................................................................................6 Floor Slabs ....................................................................................................................................6 Pavement Design Parameters .......................................................................................................6 Pavement Design ..........................................................................................................................7 Seismic Site Class .........................................................................................................................8 Earthwork .....................................................................................................................................8 Caving Considerations ..................................................................................................................9 Fill Placement ...............................................................................................................................9
LIMITATIONS ................................................................................................................................9
FIGURE
Figure 1 – Boring Location Plan
APPENDIX
General Notes /Narrative of Drilling Operations Boring Logs (8) Exploration Procedures Laboratory Procedures Grain Size Distribution Curves (5) Liquid and Plastic Limits Test Report (1 Page) Moisture Density Test Report (1) CBR Sample Worksheet (1- Page) CBR Data Sheet (4-Pages)
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EXECUTIVE SUMMARY
United Consulting has completed a Geotechnical Exploration on the proposed Murphy Express Site, 5800 West Street and 6200 South Street in West Valley, Salt Lake Valley County, Utah. The results from this assessment are briefly summarized below. The text of the report should be reviewed for a discussion of these items.
TYPICAL DEPTHS GENERAL SUBSURFACE CONDITIONS ENCOUNTERED
Below Ground Surface-20’ Firm to very dense sand with varying amounts of silt and gravel, and trace to some clay (Natural) (GC, SC, GP-GM).
Auger Refusal/Rock Not Encountered.
Groundwater Not Encountered.
ANTICIPATED FUTURE CUT AND/OR FILL
Based on visual Minimal grading (2 feet or less) is expected to achieve final grade.
GEOTECHNICAL CONCERNS
Groundwater We expect that seasonal high groundwater levels are more than 80 inches in the area of the site, and groundwater was not encountered within the depths explored. We recommend that the USTs be anchored to resist buoyancy forces.
Frost Heave Susceptible Soils Soils at the site are expected to be susceptible to frost heave. We recommend that foundations be set to bear at least 2.5 feet below finished grade.
Moisture Sensitive Soils Much of the on-site soils contain relatively moderate amounts of silt and clay, and are considered to be moisture sensitive. The soils will become unstable if saturated and subsequently disturbed by construction activities. The contractor should be prepared to protect exposed soils from saturation and construction disturbance.
FOUNDATION RECOMMENDATIONS
Shallow Foundation Bearing Capacity and Settlement
Foundations (spread footings or circular piers) bearing at least 2.5 feet below final grade may be designed based on a net, maximum allowable soil bearing capacity of 3,000 psf. For this bearing capacity, about 1 inch of total settlement or ½ inch of differential settlement over a 30-foot span should be expected.
PAVEMENT RECOMMENDATIONS
Recommended CBR 12.0
Standard Duty Pavement 5-inches of 4,000 psi reinforced concrete over 4-inches of GAB.
Heavy Duty Pavement 8-inches of 4,000 psi reinforced concrete over 4-inches of GAB.
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PROJECT INFORMATION
The project site is located at 5600 West Street and 6200 South Street in West Valley City, Salt Lake Valley County, Utah. The client provided a site plan, which showed the locations of the proposed building, canopy, tank pit, and associated parking and drive areas. This site plan was used as a guide to locate the boundaries of the project site. The location of the project site is shown on the attached Boring Location plan (Figure 1).
At the time of our field work, the project site was accessed via a concrete driveway to the southwest of the site from 5600 West Street. The site was a ±0.86-acre undeveloped out-parcel, and was covered with gravel and partially asphalt paved. The site was bound on the north, east and south by undeveloped land, to the west by 5600 West Street, and to the northwest by a paved drive. The areas surrounding the project site consisted of a mixture of retail facilities, the Walmart shopping center, and residential and commercial property.
No site specific topographic information was provided at the time of our exploration. Based on visual observations, the topography at the site generally sloped down from the north and west to the south and east, respectively. At the time of our field work, the area of the proposed building and canopy were covered with gravel. See the attached Boring Location Plan (Figure 1) for site and boring locations.
The proposed finished floor elevation (FFE) was not provided at the time of this geotechnical exploration. Based on visual observation of the site and surrounding areas, we anticipate that the cuts and fills will be minimal (2 feet or less) within the area of the building, canopy and the parking and drive areas.
Based on the provided site plan, we understand that the facility will have a 6/2 MPD canopy with a 1200 square-foot service station building within the central area of the site. A total of 4 parking spaces with associated drive areas will be constructed in the north-northwest area of the site. The proposed underground storage tanks (USTs) are planned in the north-northeast area of the site. We understand that the structural loads are light with maximum column and wall loads not exceeding 30 kips and 2 kips per linear foot, respectively.
If the actual loads and site grading information vary significantly from the above anticipated values, United Consulting must be contacted to determine if revisions to our recommendations should be re-evaluated and/or revised.
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PURPOSE
The purpose of this geotechnical exploration was to assess the general type and condition of the subsurface materials present at the project site and to provide recommendations to guide in site development, foundation design and quality assurance.
SCOPE
The scope of our geotechnical exploration included the following items:
1. Drilling seven Standard Penetration Test (SPT) borings, with continuous sampling in thetop 10 feet and sampling at 5 feet intervals below 10 feet to determine the nature andcondition of the subsurface soils;
2. Obtaining one bulk sample for laboratory testing;
3. Conducting laboratory testing to include one California Bearing Ratio (CBR) Test, onemodified proctor test, five moisture content, and five Unified Soil Classification System(USCS) tests;
4. Visual evaluation of the soil samples obtained during our field testing for furtheridentification and classification;
5. Determine IBC seismic site class based on average N-values
6. Analyzing the field data and laboratory results in order to provide recommended soilparameters and CBR value to be used for rigid pavement design.
7. Preparing this report to document the results of the fieldwork, laboratory testing, andrecommendations.
REGIONAL GEOLOGY
The project site is located in the Middle Rocky Mountains Province of Utah. The Middle Rocky Mountains province in northeastern Utah consists of mountainous terrain, stream valleys, and alluvial basins. It includes the north-south trending Wasatch Range, comprised mainly of pre-Cenozoic sedimentary and Cenozoic silicic plutonic rocks, and the east-west trending Uinta Mountains, comprised mainly of Precambrian sedimentary and metamorphic rocks. According to the Geologic Map of Utah, the project site and immediately surrounding areas are underlain by Quaternary alluvium and colluviums which consist of clay, sand, gravel and silt.
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USDA Soil Survey
According to the Natural Resources Conservation Services (NRCS) Soil Survey of Salt Lake Valley County, Utah, soils at the project site are classified as Butterfield soils, 0 to 25% slopes (BuE). The Butterfield soils are generally classified as well drained, a seasonal high water table greater than 80 inches, and have a hydraulic permeability of about 0.00 to 0.20 inches per hour. The Butterfield soils generally have a low shrink-swell potential.
SUBSURFACE CONDITIONS
The borings initially encountered a surficial gravel layer or 2.5 to 3 inches of asphalt and 2 to 18 inches of gravel. Below the groundcover, natural soils were encountered in the borings. The natural soils generally consisted of firm to very dense sand (GC, SC, GP-GM) with varying amounts of gravel, silt and trace to some clay with the standard penetration test resistance (N-values) ranging from 11 bpf to 85 bpf.
No rock was encountered in the borings drilled to termination depths ranging from 10 to 20 feet. Groundwater was not encountered in the borings at the time of drilling. Groundwater levels should be anticipated to fluctuate with the change of seasons, during periods of very low or high precipitation, or due to changes in the floodplain or watershed upstream from the area.
The borings were backfilled with the auger cuttings upon completion of drilling for safety considerations. For a more precise description of the conditions encountered within the borings, please refer to the Boring Logs provided in The Appendix.
LABORATORY TESTING PROGRAM
One composite bulk soil sample was obtained from the auger cuttings of borings B-2, B-4 and B-5 at the approximate depths from zero to 5 feet. This sample was submitted to our laboratory for one Modified Proctor test and one CBR test. Laboratory testing for this project also included five moisture content tests, and five USCS classification tests (including wash 200 grain size tests, and Atterberg limits tests). Narrative descriptions of the laboratory tests and test results are included in The Appendix.
DISCUSSION AND RECOMMENDATIONS
The following recommendations are based on our understanding of the proposed construction, data obtained in our soil test borings, a site reconnaissance and our experience with soils and subsurface conditions similar to those encountered at this site.
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United Consulting requests the opportunity for a general review of final design documents and specifications in order to verify that earthwork and foundation recommendations have been properly interpreted and implemented in the design and specifications. We recommend that United Consulting, as the Geotechnical Engineer of Record, be consulted during construction to conduct Geotechnical Controls as the Owner's Representative. Site Preparation The project site was an open lot covered with gravel. Utilities, if present, should be properly capped off at the property boundary and removed or be re-routed around the planned new construction area. If the client wishes to leave abandoned utility pipes in place within the nonstructural areas of the site, they should be filled-in under pressure with cement grout having a minimum 28-days compressive strength of 500 pounds per square inch (psi). All trench excavations resulting from removal of utility lines should be backfilled with engineered fill. Following lowering the site grade where needed and prior to placement of additional fill, foundation, or slab, we recommend that the existing subgrade within construction areas be proofrolled. Proofrolling should be conducted under the observation of the Geotechnical Engineer or his representative. Proofrolling will serve to detect soft surficial zones that will require additional treatment. Proofrolling should consist of two complete coverages in each of two perpendicular directions using a fully loaded, tandem-axle, dump truck. Areas that exhibit “pumping” during proofrolling should be treated by a method recommended by the Geotechnical Engineer. This method may consist of undercutting and backfilling with a suitable compacted fill material, replacing with surge stone and a layer of crusher run, lime stabilization, use of an appropriate geotextile or some other method that he deems suitable. Difficult Excavation No rock was encountered and we do not envision difficult excavation conditions associated with rock for this project. Conventional excavation equipment should generally be sufficient for excavation of the foundations, tank pit, and utility trenches. Groundwater Considerations Groundwater was not encountered at the time of drilling, and we expect that seasonal high groundwater levels are more than 80 inches in the area of the site. Groundwater is not generally expected to significantly impact construction activities. We envision that perched water, if encountered, can be effectively managed with sumps and pumps. The contractor should be prepared to remove perched water or groundwater as needed. We recommend that the USTs be anchored to resist buoyancy forces.
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Foundation Design and Construction
Following site preparation as recommended, the proposed lightly loaded building and canopy structure could be supported on conventional shallow foundations (square or circular piers). The shallow foundations may consist of shallow strip and/or isolated column footings supported within and underlain by suitable bearing soils. A maximum net allowable soil bearing pressure of up to 3,000 pounds per square foot (psf) is recommended. Due to the potential for frost heave, we recommend that foundations be set to bear at least 2.5 feet below existing grades.
We recommend footing widths of at least 20 inches for strip footings and 24 inches for square footings. Footings should be constructed to bear at least 2.5 feet below the lowest adjacent finished grade; greater footing depths for the canopy foundations might be required for structural considerations related to uplift and overturning resistance.
The Geotechnical Engineer must evaluate each footing excavation prior to steel reinforcement or concrete placement. Conditions that are observed should be compared to the test boring data and design requirements. If unsuitable bearing material is encountered, it should be excavated and replaced or otherwise treated as recommended by the Geotechnical Engineer.
Surface water control should be maintained to prevent accumulation of water in footing excavations. Standing water in footing excavations should be removed promptly. Soil softened by the water should be removed, and the Geotechnical Engineer or his representative should reexamine the area.
Floor Slabs
We understand that the proposed modular structure will be structurally supported and will not have a slab-on-grade. If a slab-on-grade is to be used for utility sheds or other associated structures a “conventional” slab-on-grade, designed for a subgrade modulus of 200 pounds per cubic inch (pci), may be utilized for the proposed building, provided the site is prepared as recommended.
It has been our experience that the floor slab subgrade is often disturbed by weather, foundation and utility line installation, and other construction activities between completion of grading and slab construction. For this reason, our geotechnical engineer should evaluate the subgrade shortly prior to placing the concrete. Areas judged by the Geotechnical engineer to be unstable should be re-compacted or treated as recommended by the geotechnical engineer.
Pavement Design Parameters
United Consulting recommends the following values be considered for rigid pavement design for this project.
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California Bearing Ratio = 12.0 Subgrade Reaction, k = 200 pci Pavement Subgrade shall be compacted to at least 95% of the materials maximum dry density as per standard (ASTM D-698). United Consulting recommends that the aggregate base course for pavement construction be compacted to 100% of the materials Modified Proctor (ASTM D-1557) maximum dry density. The pavement should be constructed using the materials and construction procedures of the applicable Utah Department of Transportation specifications. Pavement Design We understand that rigid concrete pavement is the only pavement type being considered for the project. We recommend the following pavement sections for the project.
TABLE 1: RECOMMENDED STANDARD DUTY PAVEMENT SECTION
Standard Duty Pavement Section Material Thickness (in)
PAVEMENT 4,000 psi reinforced concrete 5 BASE UDOT approved aggregate base 4
TABLE 2: RECOMMENDED HEAVY DUTY PAVEMENT SECTION
Heavy Duty Pavement
Section Material Thickness (in) PAVEMENT 4000 psi reinforced concrete 8
BASE UDOT approved aggregate base 4 The heavy rigid pavement section is recommended in trash dumpster pad areas and areas where heavy trucks will maneuver. The pavement should be constructed using the materials and construction procedures of the applicable Utah Department of Transportation specifications. For the subgrade preparation recommended, these pavement sections should be suitable for the anticipated traffic loads. The heavy rigid pavement section is recommended over the tank pits and trash dumpster pad areas where heavy trucks will maneuver even if standard duty pavement is used elsewhere on the project. Reinforcement and appropriate joint spacing within the concrete pavements should be determined by the project designer. The reinforced area over the UST should extend at least 10 feet beyond the limits of the UST excavation. The most critical factor in providing long-term serviceability for a pavement is a well-prepared, uniform subgrade. The long-term effects of localized areas of improperly prepared subgrade may cause cracking or potholes to develop in the pavement. Even though the potholes will affect only limited parts of the total pavement area, the overall pavement serviceability will be significantly reduced.
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Pavement should be installed late in construction when most heavy construction traffic such as concrete trucks, material delivery trucks, etc. will no longer come on site. If desired, a layer of base course can be placed earlier to provide a working surface. The site should then be proofrolled again, new soft areas treated, the base leveled and thickened as required, and the site paved at the end of construction. The most critical factor in providing long-term serviceability for a pavement is a well-prepared, uniform subgrade. The long-term effects of localized areas of improperly prepared subgrade may cause cracking or potholes to develop in the pavement. Even though the potholes will affect only limited parts of the total pavement area, the overall pavement serviceability will be significantly reduced. Pavement should be installed late in construction when most heavy construction traffic such as concrete trucks, material delivery trucks, etc. will no longer come on site. Existing Asphalt Drive The existing asphalt road was noted to be mostly in fair to good condition. In the areas explored, the pavement section consisted of 2.50 to 3.00 inches of asphalt with 18 inches of graded aggregate base (GAB). Below the existing pavement, the soils encountered consisted of sand with varying amount of silt and gravel, and traces of clay. Based on the soil types encountered and the soil consistency observed during our testing, most of the soils in their current condition are believed to have well compacted. Based on our analysis, the existing pavement sections will be sufficient for car traffic and up to four, 18 wheel trucks per day. Seismic Site Class The seismic design is covered by the provisions of the 2012 International Building Code (IBC), and Chapter 20 of ASCE 7, Site Class Definitions. The site categories referenced in the IBC are defined in terms of the average shear wave velocity (Vs) in the top 100 ft of the profile. In absence of shear wave velocities, geotechnical parameters such as standard penetration resistance (N-values) and the undrained shear strength (Su) can be utilized. Based on the average N values from our boring data, we recommend that a seismic site classification of “Site Class C” for the indicated site. This recommendation is based on the soil below depths of 20 feet to be consistent (soil type and consistency) with those encountered in the top 20 feet. No deep borings were performed at this site. A site class determination based on the average N values is necessarily conservative. Earthwork Based on the results of the laboratory testing program and our visual classification, the soils at the site are generally considered to be suitable for reuse as engineered fill with proper moisture control. Much of the on-site soils contain relatively moderate amounts of silt and clay, and are considered to be moisture sensitive. The soils will become unstable if saturated and
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subsequently disturbed by construction activities. The contractor should be prepared to protect exposed soils from saturation and construction disturbance. Positive drainage should be maintained at all times to prevent saturation of exposed soils in case of sudden rains. Rolling the surface of disturbed soils will also improve runoff and reduce the potential for construction delays due to undercutting and/or stabilization of saturated soils. Caving Considerations All excavations should be conducted in accordance with the Occupational Safety and Health Administration (OSHA) guidelines. Flattening of the excavation sidewalls and/or the use of bracing may be needed to maintain stability during construction. Fill Placement Moisture-density determinations should be performed for each soil type used to provide data necessary for quality assurance testing. The natural moisture content at the time of compaction should be within moisture content limits, which will allow the required compaction to be obtained. This is generally within three percentage points of the optimum moisture. The contractor should be prepared to increase or decrease soil water content. Typical restrictions on suitable fill are no organics, plasticity index less than 20, and maximum particle size of four inches, with not more than 20 percent greater than ¾-inch. The fill should be placed in thin lifts and then compacted. We recommend that fill be compacted to at least 95 percent of Modified Proctor (ASTM D 1557) maximum dry density. A representative of the Geotechnical Engineer must monitor fill placement on a full-time basis. In-place density tests performed by that individual will evaluate the degree of compaction being attained.
LIMITATIONS This report is for the exclusive use of Greenberg Farrow, Murphy Oil USA and the designers of the project described herein, and may only be applied to this specific project. Our conclusions and recommendations have been prepared using generally accepted standards of Geotechnical Engineering practice in the State of Utah. No other warranty is expressed or implied. Our firm is not responsible for conclusions, opinions or recommendations of others. The right to rely upon this report and the data within may not be assigned without UNITED CONSULTING’S written permission. The scope of this evaluation was limited to an evaluation of the load-carrying capabilities and stability of the subsoils. Oil, hazardous waste, radioactivity, irritants, pollutants, molds, or other dangerous substance and conditions were not the subject of this study. Their presence and/or absence are not implied or suggested by this report, and should not be inferred.
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Our conclusions and recommendations are based upon design information furnished us, data obtained from the previously described exploration and testing program and our past experience. They do not reflect variations in subsurface conditions that may exist intermediate of our borings and in unexplored areas of the site. Should such variations become apparent during construction, it will be necessary to re-evaluate our conclusions and recommendations based upon “on-site” observations of the conditions. If the design or location of the project is changed, the recommendations contained herein must be considered invalid, unless the changes are reviewed by our firm, and our recommendations are either verified or modified in writing. When design is complete, we should be given the opportunity to review the foundation plan, grading plan, and applicable portions of the specifications to see if they are consistent with the intent of our recommendations. UNITED CONSULTING
APPENDIX
General Notes /Narrative of Drilling Operations Boring Logs (8)
Exploration Procedures Laboratory Procedures
Grain Size Distribution Curves (5) Liquid and Plastic Limits Test Report (1-page)
Moisture Density Test Report (1) CBR Sample Worksheet (1-page)
CBR Data Sheet (4-pages)
EXPLORATION PROCEDURES Eight (8) Standard Penetration Test (SPT) borings (numbered B-1 through B-8) were drilled at the approximate locations shown on the attached Boring Location Plan (Figure 1). Borings B-5 and B-6 were drilled on the canopy area to depths of 20 feet; borings B-4 and B-7 were drilled at two corners of the proposed building to depths of 20 feet. Boring B-2 was drilled in the proposed tank pit area to a depth of 20 feet, and borings B-1 and B-3 were drilled on the proposed parking and drive area to depths of 10 feet. Boring B-8 was drilled on the existing pavement located at northeast area of the site to determine the thickness of the asphalt and gravel. Soil samples obtained using the split spoon sampler were examined by the geotechnical engineer and classified according to the visual-manual procedure described in ASTM D 2488-00. Soil test borings were performed in general accordance with ASTM D 1586. A narrative of field operations is included in The Appendix. The borings were located in the field by the staff engineer based on a site plan prepared by client. The boring locations were established by measuring distances from existing curb lines and other features adjacent to the project site. The boring locations are shown on the attached Boring Location Plan and should be considered approximate. The borings were backfilled after completion of drilling.
LABORATORY PROCEDURES California Bearing Ratio (CBR) The California Bearing Ratio, generally abbreviated to CBR, is a punching shear test and is a comparative measure of the shearing resistance of a soil. The CBR is a semi-empirical index of the strength and deflection characteristics of a soil that has been correlated with pavement performance to establish pavement thickness design curves. The CBR is used with these empirical curves to select thickness of pavement components (i.e., surface course, base course, and sub base). CBR tests were run generally as described in ASTM D 1883. A representative sample was compacted at the optimum moisture content as determined per ASTM D-698 Standard Proctor. The test was performed on a 6-inch diameter, 4.585-inch thick disc of compacted soil that was confined in a cylindrical steel mold. CBR tests may be run on the compacted samples in either soaked or non-soaked conditions, a soaked test was performed for this project. During testing, a piston apparently 2 inches in diameter is forced into the soil sample at the rate of penetration 0.05 inches per minute. The CBR number is obtained as the ratio of the load to penetrate the sample to a certain depth to the load required to penetrate a standard sample of crushed stone to a sample depth. The CBR number is usually based on the load ratio for a penetration of 0.10 inches. If, however, the CBR value at a penetration of 0.20 inches is significantly larger, the test is redone. If a second test also yields a larger CBR number at 0.20 inches, the CBR for 0.20 inches is used. The design CBR value is estimated from a plot of Dry Density versus CBR values for 0.1-inch and 0.2-inch penetration. Design values corresponding to a CBR value interpolated at 95% Maximum Dry Density of Standard Proctor test (ASTM D698) is also included in the Appendix.
Standard / Modified Proctor This test determines the maximum dry density that could be achieved by using uniform compaction effort at varying moisture contents. Two primary methods of compaction are used. For standard Proctor, 5.5-lb. rammer is dropped 12 inches and for modified Proctor, 10-lb. rammer is dropped 18 inches for compaction on the bulk sample in the cylindrical mold. Compaction is done in 3 and 5 equal layers respectively. The methods are explained in ASTM D 698 and ASTM D 1557, respectively. The results of the Standard Proctor tests are included in The Appendix. Grain Size (Sieve) Analysis with or without Hydrometer Grain Size Analysis tests were performed to determine the particle size distribution of selected samples tested. The grain size distribution of soils coarser than a number 200 sieve was determined by passing the samples through a standard set of nested sieves. Materials finer than the number 200 sieves were suspended in water and the grain size distribution computed from
the time rate of settlement of the different size particles. Air-dried soil passed through a #200 sieve. 50 grams of that must soak in s/c agent for a minimum of 8 hours. Soil is then put in graduated cylinder with a hydrometer. Readings are taken at specified times. A graph is drawn from data. These tests were similar to those described by ASTM D 421 and D 422. The results are included in The Appendix. Unified Soil Classification System (USCS) Soils to be classified as per Unified Soil classification System (USCS) are generally required to perform grain size analysis (particle size distribution), liquid limit and plasticity index tests when precise classification is required. After performing the required tests, the classification is generally performed in accordance with ASTM D 2487. These classification tests are typically required by GDOT in the areas of construction of new pavement over existing paved shoulders, areas of muck, swamp, lake/pond bottom, etc. The results are included in The Appendix. Liquid and Plastic Limits (Atterberg Limits) Liquid Limit and Plastic Limit tests aid in the classification of the soils and provide an indication of the soil behavior with moisture change. The Plasticity Index is bracketed by the Liquid Limit (LL) and the Plastic Limit (PL). The Liquid Limit is the moisture content at which the soil will flow as a heavy viscous fluid and is the upper limit of the plastic range, as determined in accordance with ASTM D 4318. The Plastic Limit is the moisture content at which the soil begins to lose its plasticity, as determined in accordance with ASTM D 4318. The Plasticity Index is the difference between the Liquid Limit and Plastic Limit. The Liquidity Index is the ratio of the difference between the in-place moisture and the plastic limit to the Plasticity Limit. The data obtained are in the Appendix. Moisture Content The moisture content was determined for selected soil samples obtained in the split spoon sampler. A representative portion of each sample was weighed and then placed in an oven and dried at 110 degree Centigrade for at least 15 to 16 hours. After removal from the oven, the soil was again weighed. The weight of the moisture lost during drying thus was determined. From this data, the moisture content of the sample was then calculated as the weight of moisture divided by dry weight of the soil, expressed as a percentage. This test was conducted according to ASTM D 2216. The moisture content results are indicated on the attached boring logs. Moisture content is a useful index of a soil’s compressibility. If the soil is to be used as fill, the moisture content may be compared to the range of water content for which proper compaction may be achieved.
