cive.4310 shallow foundation settlement
TRANSCRIPT
Slide 1Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
Figures after Crawford, 1972 (CBD-148)
TYPES OF SETTLEMENTL L L
UniformSettlement
Tilt Non-UniformSettlement
DD
Where:
St = Total Settlement(Typically limited to 1 inch)
D = Maximum Differential SettlementL = Building (or Span) LengthDeflection Ratio = D/L
Table 2-1. Maximum Allowable St (EM 1110-1-1904)
St
Slide 2Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
Figures after Crawford, 1972 (CBD-148)
TYPES OF SETTLEMENTL L L
UniformSettlement
Tilt Non-UniformSettlement
DD
Where:
St = Total SettlementD = Maximum Differential SettlementL = Building (or Span) LengthDeflection Ratio = D/L
Table 2-2. Limiting D/L (EM1110-1-1904)
St
Slide 3Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
Figure 2-1. EM1110-1-1904
DIFFERENTIAL SETTLEMENT
Where:
D = Max. Differential Settlementd = Differential Settlement between 2 PtsL = Building (or Span) Lengthl = Length between 2 PointsAngular Distortion b = d/l
Differential Settlement
Interference w/ Adjacent StructuresDisruption of Machinery & PeopleCrackingJammed Floors & WindowsUneven FloorsReduction of waterstop efficiencyStructural Failure
Slide 4Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
Figure 2-1. EM1110-1-1904
DIFFERENTIAL SETTLEMENT
Table 2-3. Limiting b/l to Avoid Damage(EM1110-1-1904)
*Based on field surveys of damage
Slide 5Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
Figure 2-1. EM1110-1-1904
DIFFERENTIAL SETTLEMENT
Table 2-3. Empirical Correlations between D and b (EM1110-1-1904)
Slide 6Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
Figure 1-3. EM1110-1-1904
FOUNDATION CONTACT PRESSURESRIGID FOUNDATIONS
Typically ExperienceUniform Settlement
FLEXIBLE FOUNDATIONSTypically Experience
Differential Settlement
Figure 12-14. Das FGE (2005)
Slide 7Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
WHAT DO YOU NEED TO CALCULATE SETTLEMENT?
FOUNDATION SETTLEMENT COMPONENTS
Total Foundation Settlement = Elastic Settlement + Consolidation Settlement
a.k.a. Immediate.Primary Settlement Component
of Sands but also occurs inCohesive Soils.
a.k.a. Long-Term.Primary Settlement Component
of Cohesive Soils.Covered in Soil Mechanics
St = Se + Sc
Foundation Loads/PressuresChanges in Vertical Soil Stress (Ds)Foundation Size and LocationSoil ProfileSoil Properties:
Elastic Settlement: Es, mConsolidation Settlement: 1D Consolidation Test Data
Slide 8Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
Boussinesq DistributionsFigure 1-2. EM 1110-1-1904
STRIP
VERTICAL STRESS INCREASE (Ds) IN SOILS (REVIEW)
SQUARE
Westergaard DistributionsFigure 11. NAVFAC DM7.01
Slide 9Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
APPROXIMATE 2V:1H DISTRIBUTION METHOD
))(( zLzB
Q
Ds
Figure C-1. EM1110-1-1904
Where:
Ds = Change in Total VerticalStress
Q = Applied Foundation LoadB = Foundation WidthL = Foundation Length
VERTICAL STRESS INCREASE (Ds) IN SOILS (REVIEW)
Slide 10Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
Table C-1. Boussinesq Solutions (EM 1110-1-1904).
VERTICAL STRESS INCREASE (Ds) IN SOILS (REVIEW)
Slide 11Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
Table C-1. Boussinesq Solutions (EM 1110-1-1904).
VERTICAL STRESS INCREASE (Ds) IN SOILS (REVIEW)
Slide 12Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
VERTICAL STRESS INCREASE (Ds) IN SOILS (REVIEW)
Table C-1. Boussinesq Solutions (EM 1110-1-1904).
Slide 13Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
Figures courtesy of http://www.taunton.com
VERTICAL STRESS INCREASE (Ds) IN SOILS
Depth of Influence of Ds for Settlement Calculations
SQUARE: Depth = 2B STRIP: Depth = 4B
Slide 14Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
VERTICAL STRESS INCREASE (Ds) IN SOILSDepth of Influence of Ds for Settlement Calculations
Slide 15Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
21 1
21FFI
s
ss m
m
Se qo a ¢B( )1ms2
Es
IsI fWhere:
Se = Elastic Settlementqo = Contact Stressa = Foundation Location Factor
for Settlement under Centera = 1, m’ = L/B, n’ = H/(B/2)For Settlement under Cornera = 1, M’ = L/B, n’ = H/B
B’ = Widthuse B for Settlement @ Corneruse B/2 for Settlement @ Center
General Elastic Relation(Flexible Foundation):
ms = Soil Poisson’s RatioEs = Soil Elastic ModulusIs = Shape Factor
f(ms, F1, F2) – Table 12.3 Das FGE (2005)
If = Depth Factorf(Df/B, ms, L/B) – Table 12.4 Das FGE (2005)
General Elastic Relation(Rigid Foundation):
),(93.0 centerflexibleee SS
ELASTIC SETTLEMENT OF SOIL
Slide 16Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
( )2/;'B
Hn
B
Lm ¢
ELASTIC SETTLEMENT OF SOIL – TABLE 12.3 Das (2005)
B
Hn
B
Lm ¢ ;'Center of
Footing:Corner ofFooting:
H = Depth to rigid layer
Slide 17Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
ELASTIC SETTLEMENT OF SOIL – TABLE 12.4 Das (2005)
Slide 18Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
ELASTIC SETTLEMENT OF SOIL – TABLE 12.4 Das (2005)
Slide 19Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
ELASTIC PARAMETERS OF SOIL
Table 12.5. Typical Elastic Parameters of Soils(Das FGE (2005)
Table D-3. Typical Soil Elastic Moduli(EM1110-1-1904)
Slide 20Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
Se qo(1n
2 ) ¢A144Esbz
Where:
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:
ELASTIC SETTLEMENT OF SOIL (AASHTO, 2010)
n = Soil Poisson’s Ratio(See Article 10.4.6.3 if directmeasurements are not available)
bz = 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.
Slide 21Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
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
Slide 22Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
DD
ZM
SDMT
es
ELASTIC SETTLEMENT OF SOIL - DMT
Stress Distribution
Figure courtesy of Marchetti (1999) - The Flat Dilatometer (DMT) andIt's Applications to Geotechnical Design
Where:
Se = Elastic SettlementDs = Change in StressMDMT = Constrained ModulusZ = Depth
Slide 23Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
ELASTIC SETTLEMENT OF SOIL - DMT
Marchetti (1999) - The Flat Dilatometer (DMT) andIt's Applications to Geotechnical Design
Slide 24Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
Figure from Hayes (1990)
ELASTIC SETTLEMENT OF SOIL - DMT
Slide 25Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
DMT SETTLEMENT EXAMPLE (NTS)
Depth(ft)
0
10.2GWT 10 ft
Silty Sand (SM)gt = 115 pcf, f' = 34°
3ft Sq. ColumnQ = 27 kips
Df = 1ft Df = 1ft
2ft x 4.5 ft Column FootingQ = 27 kips
Determine Settlement of Both Footings using the provided
DMT Data
Slide 26Revised 03/2020
CIVE.4310 FOUNDATION & SOIL ENGINEERINGSHALLOW FOUNDATIONS - SETTLEMENT
DMT SETTLEMENT
EXAMPLE
DMT Data