Slide 1 of 43Revised 02/2013
14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
• Soil Borings.• Geotechnical Report (not covered).• Bearing Pressure Calculations.• Settlement Calculations.• Lateral Earth Pressure Calculations.• Retaining Wall Design Review.
OVERVIEWREVIEW OF 14.431 FOUNDATIONS & SOILS ENG.
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
OVERVIEW: BORINGS
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
• Very common test worldwide• 1902 - Colonel Gow of Raymond Pile
Co.• Split-barrel sample driven in borehole.• Conducted on 2½ to 5 ft depth intervals• ASTM D1586 guidelines• Drop Hammer (140 lbs falling 30 inches)• 3 or 4 increments of 6 inches each
– Three (3) Increments: Sum of last two increments = “SPT N value" (blows/ft)
– Four (4) Increments: Sum of last two increments = “SPT N value" (blows/ft)
• Correlations available with all types of soil engineering properties
• Disturbed Soil Samples Collected
STANDARD PENETRATION TEST (SPT) (ASTM D1586-11)
Text modified from FHWA NHI Course 132031 Subsurface Investigations
Marking of 6 inch Increments for SPT Test Photograph courtesy of physics.uwstout.edu
Slide 4 of 43Revised 02/2013
14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
Figures courtesy of J. David Rogers, Ph.D., P.E., University of Missouri-Rolla & FHWA NHI Course 132031
Typical Setup
Split Spoon Dimensions (after ASTM D1586)
STANDARD PENETRATION TEST (SPT) (ASTM D1586-11)
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
Figure courtesy of FHWA NHI Course 132031 Subsurface Investigations
STANDARD PENETRATION TEST (SPT) (ASTM D1586-11)
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
Figure courtesy of http://www.civil.ubc.ca
STANDARD PENETRATION TEST (SPT) (ASTM D1586-11)
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
STANDARD PENETRATION TEST (SPT)Factors Affecting SPT (after Kulhawy & Mayne, 1990 & Table 8. FHWA IF-02-034 )
Cause Effects Influence on N Value
Inadequate Cleaning of Borehole SPT not made in insitu soil, soil trapped, recovery reduced Increases
Failure to Maintain Adequate Head in Borehole Bottom of borehole may become quick Decreases
Careless Measure of Drop Hammer Energy varies Increases
Hammer Weight Inaccurate Hammer Energy varies Inc. or Dec.
Hammer Strikes Drill Rod Collar Eccentrically Hammer Energy reduced Increases
Lack of Hammer Free (ungreased sleeves, stiff rope, more than 2 turns on cathead, incomplete release of drop, etc.) Hammer Energy reduced Increases
Sampler Driven Above Bottom of Casing Sampler driven in disturbed soil Inc. Greatly
Careless Blow Count Recording Inaccurate Results Inc. or Dec.
Use of Non-Standard Sampler Correlations with Std. Sampler Invalid Inc. or Dec.
Coarse Gravel or Cobbles in soil Sampler becomes clogged or impeded Increases
Use of Bent Drill Rods Inhibited transfer of energy to sampler Increases
Slide 8 of 43Revised 02/2013
14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
CARE & PRESERVATION OF SOIL SAMPLES• Mark and Log samples upon
retrieval (ID, type, number, depth, recovery, soil, moisture).
• Place jar samples in wood or cardboard box.
• Should be protected from extreme conditions (heat, freezing, drying).
• Sealed to minimize moisture loss.• Packed and protected against
excessive vibrations and shock.
Text and Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
N
DR = relative densityT = unit weightLI = liquefaction index�' = friction anglec' = cohesion intercepteo = void ratioqa = bearing capacityp' = preconsolidationVs = shear waveE' = Young's modulus = dilatancy angleqb = pile end bearingfs = pile skin frictionSAND
cu = undrained strengthT = unit weightIR = rigidity index�' = friction angleOCR = overconsolidationK0 = lateral stress stateeo = void ratioVs = shear waveE' = Young's modulusCc = compression indexqb = pile end bearingfs = pile skin frictionk = permeabilityqa = bearing stress
CLAY
Courtesy of FHWA NHI Course 132031 Subsurface Investigations
What Do We Need? How Do We Get It?
STANDARD PENETRATION TEST (SPT)
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
CORRECTIONS TO SPT N VALUENmeasured = Raw SPT Value from Field Test (ASTM D1586-11)N60 = Corrected N values corresponding to 60% Energy Efficiency
(i.e. The Energy Ratio (ER) = 60% (ASTM D4633-10)Note: 30% < ER < 100% with average ER = 60% in the U.S.
Factor Term Equipment Variable Correction
Energy Ratio CE = ER/60Donut HammerSafety Hammer
Automatic Hammer
0.5 to 1.00.7 to 1.20.8 to 1.5
Borehole Diameter CB
65 – 155 mm150 mm200 mm
1.001.051.15
Sampling Method CSStandard Sampler
Non-Standard Sampler1.0
1.1 to 1.3
Rod Length CR
3 – 4 m4 – 6 m6 – 10 m> 10 m
0.750.850.951.00
N60 = CECBCSCRNmeasured
For Guidance Only. Actual ER values should be measured per ASTM D4633
SPT Corrections(From Table 9,
FHWA IF-02-034)
Slide 11 of 43Revised 02/2013
14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
Data from Robertson, et al. (1983), Courtesy of FHWA NHI Course 132031 Subsurface Investigations
4
6
8
10
12
14
16
0 10 20 30 40 50
Measured N-values
Dep
th (m
eter
s)
Donut
Safety
Sequence
ER = 34 (energy ratio)
45
40
41
41
39
47
56
5560
5663
63
63
64
69
4
6
8
10
12
14
16
0 10 20 30 40 50
Corrected N60
Dep
th (m
eter
s)
Donut
Safety
Trend
CORRECTIONS TO SPT N VALUETWO BORINGS/ONE SITE EXAMPLE:
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
NORMALIZED SPT N VALUE (N1)60(N1)60 = N60 values normalized to 1 atmosphere overburden
stress.
(N1)60 = CNN60
Where:CN = (Pa/'vo)n
Pa = Atmospheric Pressure (1 atm = 14.7 psi = 2116 psf)'vo = Insitu Vertical Effective Stress
n = 1 (clays) and 0.5 to 0.6 (sands)
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
Triaxial Database from Frozen Sand Samples
20
25
30
35
40
45
50
55
0 10 20 30 40 50 60Normalized (N1)60
Frict
ion
Ang
le,
' (de
g)
Sand (SP and SP-SM)
Sand Fill (SP to SM)
SM (Piedmont)
H&T (1996)
' = [15.4(N1)60]0.5+20
EFFECTIVE FRICTION ANGLE (') FOR SANDS - SPT
Figure 9-12. FHWA NHI Course 132031 Subsurface Investigations
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
SOIL SHEAR STRENGTH CORRELATIONSFROM IN-SITU TESTING
Shear Strength
Parameter
Insitu Testing Method
SPT CPT DMT
Effective Soil Friction
Angle (′)
See Slide 15 arctan[0.1+0.38log(qt/′vo)] 28°+14.6°log(KD)-2.1°log2KD
See Slide 15 Robertson and Campanella(1983)
Marchetti et al. (2001)ISSMGE TC 16 Report
Undrained Shear
Strength (Su)
NO ACCEPTABLE CORRELATIONS
(qt-vo)/Nkt(Nkt = 15 for CHS) 0.22′vo(0.5KD)1.25
Aas et al. (1986) Marchetti et al. (2001)ISSMGE TC 16 Report
NOTES:1. (N1)60 = N60(Pa/′vo)0.5 for sands. Pa = Atmospheric Pressure = 1 bar ≈ 1 tsf.2. ′vo = Insitu Effective Overburden Pressure = Insitu Vertical Effective Stress.3. vo = Total Overburden Pressure = Insitu Vertical Total Stress.
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
Equation Reference
' = 54° - 27.6034*exp(-0.014(N1)60)
Peck, Hanson, & Thorton (1974) from Kulhawy & Mayne (1990)
' = [20*(N1)60]0.5 + 20°for 3.5 (N1)60 30
Hatanaka & Uchida (1996)
' = 27.1° +0.3*(N1)60 –0.00054(N1)2
60
Peck, Hanson, & Thorton (1974)
from Wolff (1989)
' = [15.4(N1)60]0.5 + 20°Mayne et a. (2001)
based on Hatanaka &
Uchida (1996)
' = [15(N1)60]0.5 + 15°for (N1)60 > 5 and 45°
JRA (1996)
Effective Soil Friction Angle (′) Summary from NCHRP Report 651 (2010)
SOIL SHEAR STRENGTH CORRELATIONSFROM IN-SITU TESTING
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
after Fang et al. (1991) and EM 1110-1-1905.NOTE: 1 MPa = 10.44 tsf
Soil Density/Consistency N qt(MPa)
t(pcf)
′(°)
SANDS
V. Loose 0-4 0-2 90-105 <30
Loose 5-10 2-5 95-110 30-35
Medium Dense 11-30 5-15 105-120 35-38
Dense 31-50 15-25 115-130 38-41
Very Dense >50 >25 125-140 41-44
COHESIVE SOILS
Very Soft 0-2 0-0.5 90-100
NA
Firm 2-8 0.5-1.5 90-110
Stiff 9-15 1.5-3 105-125
Very Stiff 15-30 3-6 115-135
Hard >30 >6 120-140
SOIL ENGINEERING PROPERTY CORRELATIONS FROMIN-SITU TESTING (TABLE 1)
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
N160 = CNN60Where:
CN = [0.77log10(40/'vo)](CN < 2.0)'vo = Insitu Vertical Effective Stress (ksf)N60 = SPT Blow Count corrected for hammer eff.
N160 f (°)<4 25-304 27-32
10 30-3530 35-4050 38-43
Table 10.4.6.2.4-1. N160 vs. f(after Bowles, 1977).
* Assume ER = 60% (Cathead) & 80% (Automatic)
NORMALIZED SPT N VALUE N160(AASHTO 2010)
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
AASHTO (2010) 10.6 – SPREAD FOOTINGS10.6.1.3 – Effective Footing Dimensions
Figure C10.6.1.3.1. – Reduced Footing Dimensions.
B’ = B – 2ebL’ = L – 2eL
Where:eb = Eccentricity parallel to
Dimension B.eL = Eccentricity parallel to
Dimension L.
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
AASHTO (2010) 10.6 – SPREAD FOOTINGS10.6.3.1 – Bearing Resistance of Soil
qR = φb qnWhere:
qR = Factored Resistanceφb = Resistance Factor
(see Article 10.5.5.2.2)qn = Nominal Bearing Resistance
= qult in 14.431
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
REVIEW – BEARING CAPACITY EQUATION(after Meyerhof, 1963)
qu = c'NcFcsFcdFci + qNqFqsFqdFqi + 0.5BNFsFdFi
CohesionComponent
Surcharge ComponentSoil Above Footing
Soil ComponentSoil BelowFooting
Where:c' = Soil Cohesion Nc = Bearing Capacity Factor - Cohesionq = Surcharge = Df Nq = Bearing Capacity Factor - Surcharge = Soil Unit Weight N = Bearing Capacity Factor – Soil B = Footing WidthFcs, Fqs, Fs = Shape FactorsFcd, Fqd, Fd = Depth FactorsFci, Fqi, Fi = Inclination Factors
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
BEARING CAPACITYFACTORS
(Dimensionless, based on ')
0 5 10 15 20 25 30 35 40 45Effective Friction Angle (') (°)
1
10
100
2
4
6
8
20
40
60
80
Bea
ring
Cap
acity
Fac
tor (
Nc,
Nq,
N)
0 5 10 15 20 25 30 35 40 45
1
10
100
2
4
6
8
20
40
60
80
Nc
Nq
N
Nc
Nq
N
cot1qc NN
tan12 qNN
tan2
245tan eNq
Also see Table 12.1, Das FGE (2006) forTabular Data
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
BEARING CAPACITY FACTORS (Table 12.1 Das FGE 2006)
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
Factor Cohesion Surcharge Unit Weight
Shape(De Beer, 1970)
Depth(Df/B ≤1)
(Hanson, 1970)
Depth(Df/B >1)
(Hanson, 1970)
InclinationHanna &
Meyerhof (1981)
= Inclination of Load with respect to verticalThe factor tan-1(Df/B) is in radians
BD
F fqd
12 tansin1tan21
BD
F fcd 4.01
1iF
1dF
tan1LBFqs
c
qcs N
NLBF 1
LBF s 4.01
BD
F fcd
1tan4.01
B
DF f
qd2sin1tan21
2
901
qiF
1dF
2
901
ciF
BEARING CAPACITY FACTORS
Slide 24 of 43Revised 02/2013
14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
BEARING CAPACITY EQUATION(AASHTO LRFD Design Specifications, 5th Ed., 2010)
qn = cNcm + DfNqmCwq + 0.5BNmCwCohesionComponent
Surcharge ComponentSoil Above Footing
Soil ComponentSoil BelowFootingWhere:
c = Undrained Shear StrengthNcm = NcscicNc = Cohesion BCF for
undrained loading (see Table 10.6.3.1.2a-1)
sc = Footing Shape Correction Factor (see Table 10.6.3.1.2a-3)
ic = Load Inclination Factor (Eq. 10.6.3.1.2a-5 or 6)
= Moist Unit Weight of soil above footing
Df = Footing Embedment Depth
Nqm = NqsqdqiqNq = Surcharge BCF (see
Table 10.6.3.1.2a-1)sq = Footing Shape Correction
Factor (see Table 10.6.3.1.2a-3)
dq = Depth Correction Factor (see Table 10.6.3.1.2a-4)
iq = Load Inclination Factor (Eq. 10.6.3.1.2a-7)
Cwq = Groundwater CF (Table 10.6.3.1.2a-2)
= Moist Unit Weight of soil below footing
B = Footing WidthNm = NsiN = Unit Weight BCF (see
Table 10.6.3.1.2a-1)s = Footing Shape Correction
Factor (see Table 10.6.3.1.2a-3)
i = Load Inclination Factor (Eq. 10.6.3.1.2a-8)
Cw = Groundwater CF (Table 10.6.3.1.2a-2)This is Munfakh et al. (2001)
for determining φb
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
Material USCS qall (ksf)
Crystalline Bedrock 12
Sedimentary and Foliated Rock 4
Sandy Gravel and/or Gravel GW & GP 3
Sand, Silty Sand, Clayey Sand, Silty Gravel, & Clayey Gravel
SW, SP, SM, SC, GM, GC 2
Clay, Sandy Clay, Silty Clay, Clayey Silt, Silt, and Sandy Silt CL, CH, ML, MH 1.5
Mud, Organic Silt, Organic Clays, Peat, and Unprepared Fill TBD
PRESUMPTIVE MAXIMUM ALLOWABLE BEARING PRESSURES(from Table 1804.2, IBC 2006)
See also Table 1 NAVFAC DM7.02 (p. 142) andTable C10.6.2.6.1-1 AASHTO (2010).
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
AASHTO (2010) 10.6 – SPREAD FOOTINGSOther Bearing Capacity Considerations
Figure C10.6.1.3.2b-1.Punching Failure
(Reduction in Shear Strength)Figure C10.6.1.3.2c-1 (& c-2).
Footing on Slopes(Reduction in Bearing Factors)
Figure C10.6.1.3.2e-2.Footing on Two Layer Soil
Systems (Dependent).
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
scet SSSS Where:
St = Total SettlementSe = Elastic SettlementSp = Primary Consolidation SettlementSs = Secondary Consolidation Settlement
AASHTO (2010) 10.6 – SPREAD FOOTINGS10.6.2.4.2 – Settlement Analysis
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
Se qo(1
2 ) A144EszWhere:
Se = Elastic Settlementqo = Applied Vertical Stress (ksf)A’ = Effective Area of Footing (ft2)Es = Young’s Modulus of Soil (ksi)
(See Article 10.4.6.3 if directmeasurements are not available)
Elastic Half-SpaceMethod:
= Soil Poisson’s Ratio(See Article 10.4.6.3 if directmeasurements are not available)
z = Shape Factor (dimensionless)(As specified in Table 10.6.2.4.2-1)
Unless Es varies significantly with depth, Es should be determined at a depth of about ½ to 2/3 of B below the footing. If the soil modulus varies significantly with depth, a weighted average value of Es should be used.
AASHTO (2010) 10.6 – SPREAD FOOTINGS10.6.2.4.2 – Settlement (Cohesionless Soils)
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
Figure courtesy of Marchetti (1999) - The Flat Dilatometer (DMT) andIt's Applications to Geotechnical Design
ELASTIC SETTLEMENT OF SOIL (DMT)
Uses Direct Measurement
of Soil to Calculate
Settlement
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
ZM
SDMT
e
Stress Distribution
Figure courtesy of Marchetti (1999) - The Flat Dilatometer (DMT) and It's Applications to Geotechnical Design
Where:Se = Elastic Settlement = Change in StressMDMT = Constrained ModulusZ = Depth
ELASTIC SETTLEMENT OF SOIL (DMT)
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
LATERAL EARTH PRESSURESCOULOMB OR RANKINE REVIEW
Rankine “State of Stress” Theory:• Does not account for wall friction.• Requires vertical wall.• Conservative relative to other
methods.• Fixed plane of failure.• Favored by the transportation
agencies (AASHTO and FHWA) . See AASHTO Standard Specifications for Highway Bridges.
Coulomb “Wedge”Theory:• Accounts for wall friction.• Unique failure angle for each design.• Used by National Masonry Concrete
Association (NCMA) & USACE.• Inaccurate passive earth pressures
w/large wall angles or friction angle (particularly for ' > ' /2) .
• Decreased accuracy w/ depth.• Calculates lower active earth
pressure than Rankine for level backslope.
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
ap
p
p
a
a
KK
K
K
K
K
1
)2/45(tansin1sin1
)2/45(tansin1sin1
2
2
LATERAL EARTH PRESSURESCOULOMB OR RANKINE REVIEW
RankineCoulomb
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
LATERAL EARTHPRESSURES
COULOMB ORRANKINE?
Figure C3.11.5.3-1 –Application of (a) Rankine
and (b) Coulumb Earth Pressure Theories in
Retaining Wall Design (AASHTO 2012).
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
REVIEW: RETAINING WALL DESIGN ANALYSES
Overturning Sliding(Strength)
Figure 13.4. Das FGE (2005) and Figure C11.6.2.3-1 (AASHTO 2012).
BearingCapacity(Strength)
Overall Stability(Service)
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
AASHTO (2010) SECTION 11 – ABUTMENTS11.5.2 – Service Limit States
Abutments, piers, and wall shall be investigated for:• Excessive vertical and lateral displacements
• Vertical: Dependent on wall• Lateral: < 1.5 inches (C11.5.2)
• Overall Stability• Can use Modified Bishop, Simplified Janbu, and Spencer
Analysis Methods (11.6.2.3)
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
AASHTO (2010) SECTION 11 – ABUTMENTS11.5.3 – Strength Limit States
Abutments and walls shall be investigated at the strength limit states using Eq. 1.3.2.1-1 for:• Bearing Resistance Failure (i.e. bearing capacity)• Lateral Sliding• Excessive Loss of Base Contact• Pullout Failure of anchors and soils
reinforcements• Structural Failure
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
AASHTO (2010) SECTION 11 – ABUTMENTS11.5.5 – Load Combinations & Load Factors
Figure C11.5.5-2 – Typical Application of Load Factors for Sliding and Eccentricity.
Where:DC = Dead Load of Structural ComponentsDW = Dead Load of Wearing Surfaces and UtilitiesEH = Horizontal Earth Pressure LoadES = Earth Surcharge LoadEV = Vertical Pressure from Dead Load of Earth FillWA = Water Load and Stream Pressure
Slide 38 of 43Revised 02/2013
14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
AASHTO (2010) SECTION 11 – ABUTMENTS11.5.5 – Load Combinations & Load Factors
Figure C11.5.5-2 – Typical Application of Load Factors for Sliding and Eccentricity.
Where:DC = Dead Load of Structural ComponentsDW = Dead Load of Wearing Surfaces and UtilitiesEH = Horizontal Earth Pressure LoadES = Earth Surcharge LoadEV = Vertical Pressure from Dead Load of Earth FillWA = Water Load and Stream Pressure
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
AASHTO (2010) 11 – ABUTMENTS11.5.5 – Load Combinations & Load Factors
Figure C11.5.5-3 – Typical Application of Live Load Surcharge.
Where:LS = Live Load Surcharge
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14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
Figure 11.6.3.2.-1 – Bearing Stress Criteria for Conventional Wall Foundations on Soil.
eBV
v 2
AASHTO (2010) SECTION 11 –ABUTMENTS
11.6.3.2 – BEARINGRESISTANCE (SOIL)
Where:V = Sum of Vertical ForcesB = Footing Widthe = Eccentricity
Slide 41 of 43Revised 02/2013
14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
AASHTO (2010) SECTION 11 – ABUTMENTS11.6.3.6 – Sliding (refer to 10.6.3.4 – Failure by Sliding)
RR = φRn = φR + φepRepWhere:
RR = Factored Resistance against Failure by SlidingRn = Nominal Sliding Resistanceφ = Shear Resistance Factor (see Table 10.5.5.2.2-1)R = Nominal Shear Resistance (=V*tan)φep = Passive Resistance Factor (see Table 10.5.5.2.2-1)Rep = Nominal Passive Resistance
Slide 42 of 43Revised 02/2013
14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
AASHTO (2010) SECTION 11 – ABUTMENTS11.6.3.5 – Passive Resistance
• Neglected in Stability Calculations• Unless base of the wall extends below the depth of
maximum scour, freeze-thaw, or other disturbances• Neglected is soil providing passive resistance is,
or is likely to become, soft, loose, or disturbed, or if contact between the soil and ground is not tight.
Slide 43 of 43Revised 02/2013
14.485 CAPSTONE DESIGNModule 4 – Geotechnical Engineering
NOTE:⅓' ' < ⅔'
INTERFACIAL FRICTION ANGLES(NAVFAC DM7.02)
Section 10.6.3.4:Concrete Cast against Soil:tan = tan fPrecast Concrete Footing:tan = 0.8*tan f