Revised 2/2010

CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 1 of 25 Figures after Crawford, 1972 (CBD-148)

TYPES OF SETTLEMENT L L L

Uniform Settlement

Tilt Non-Uniform Settlement

!"!"

Where:

St = Total Settlement (Typically limited to 1 inch) ! = Maximum Differential Settlement L = Building (or Span) Length Deflection Ratio = !/L

Table 2-1. Maximum Allowable St (EM1110-1-1904)

St

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 2 of 25 Figures after Crawford, 1972 (CBD-148)

TYPES OF SETTLEMENT L L L

Uniform Settlement

Tilt Non-Uniform Settlement

!"!"

Where:

St = Total Settlement ! = Maximum Differential Settlement L = Building (or Span) Length Deflection Ratio = !/L

Table 2-2. Limiting !/L (EM1110-1-1904)

St

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 3 of 25

Figure 2-1. EM1110-1-1904

DIFFERENTIAL SETTLEMENT

Where:

! = Max. Differential Settlement # = Differential Settlement between 2 Pts L = Building (or Span) Length l = Length between 2 Points Angular Distortion $ = #/l

Differential Settlement

Interference w/ Adjacent Structures Disruption of Machinery & People Cracking Jammed Floors & Windows Uneven Floors Reduction of waterstop efficiency Structural Failure

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 4 of 25

Figure 2-1. EM1110-1-1904

DIFFERENTIAL SETTLEMENT Table 2-3. Limiting $/l to Avoid Damage (EM1110-1-1904)

*Based on field surveys of damage

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 5 of 25

Figure 2-1. EM1110-1-1904

DIFFERENTIAL SETTLEMENT

Table 2-3. Empirical Correlations between ! and $ (EM1110-1-1904)

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 6 of 25 Figure 1-3. EM1110-1-1904

FOUNDATION CONTACT PRESSURES RIGID FOUNDATIONS

Typically Experience Uniform Settlement

FLEXIBLE FOUNDATIONS Typically Experience

Differential Settlement

Figure 12-14. Das FGE (2005)

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 7 of 25

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 in Cohesive Soils.

a.k.a. Long-Term. Primary Settlement Component

of Cohesive Soils. Covered in CIVL409

St = Se + Sc

Foundation Loads/Pressures Changes in Vertical Soil Stress (!%) Foundation Size and Location Soil Profile Soil Properties: Elastic Settlement: Es, " Consolidation Settlement: 1D Consolidation Test Data

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 8 of 25

Boussinesq Distributions Figure 1-2. EM 1110-1-1904

STRIP

VERTICAL STRESS INCREASE (!%) IN SOILS (REVIEW) SQUARE

Westergaard Distributions Figure 11. NAVFAC DM7.01

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 9 of 25

APPROXIMATE 2V:1H DISTRIBUTION METHOD

Figure C-1. EM1110-1-1904

Where:

!% = Change in Total Vertical Stress Q = Applied Foundation Load B = Foundation Width L = Foundation Length

VERTICAL STRESS INCREASE (!%) IN SOILS (REVIEW)

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 10 of 25

Table C-1. Boussinesq Solutions (EM 1110-1-1904).

VERTICAL STRESS INCREASE (!%) IN SOILS (REVIEW)

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 11 of 25

Table C-1. Boussinesq Solutions (EM 1110-1-1904).

VERTICAL STRESS INCREASE (!%) IN SOILS (REVIEW)

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 12 of 25

VERTICAL STRESS INCREASE (!%) IN SOILS (REVIEW)

Table C-1. Boussinesq Solutions (EM 1110-1-1904).

Revised 2/2010

CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 13 of 25 Figures courtesy of http://www.taunton.com

VERTICAL STRESS INCREASE (!%) IN SOILS Depth of Influence of !% for Settlement Calculations

SQUARE: Depth = 2B STRIP: Depth = 4B

Revised 2/2010

CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 14 of 25

VERTICAL STRESS INCREASE (!%) IN SOILS Depth of Influence of !% for Settlement Calculations

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 15 of 25

Where: Se = Elastic Settlement qo = Contact Stress & = Foundation Location Factor for Settlement under Center & = 1, m = L/B, n = H/(B/2) For Settlement under Corner & = 1, M = L/B, n = H/B B = Width use B for Settlement @ Corner use B/2 for Settlement @ Center

General Elastic Relation (Flexible Foundation):

s = Soil Poissons Ratio Es = Soil Elastic Modulus Is = Shape Factor f(s, F1, F2) Table 12.3 Das FGE (2005)

If = Depth Factor f(Df/B, s, L/B) Table 12.4 Das FGE (2005)

General Elastic Relation (Rigid Foundation):

ELASTIC SETTLEMENT OF SOIL

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 16 of 25

ELASTIC SETTLEMENT OF SOIL TABLE 12.3 Das (2005)

Center of Footing:

Corner of Footing:

H = Depth to rigid layer

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 17 of 25

ELASTIC SETTLEMENT OF SOIL TABLE 12.4 Das (2005)

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 18 of 25

ELASTIC SETTLEMENT OF SOIL TABLE 12.4 Das (2005)

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 19 of 25

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)

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 20 of 25

Figure courtesy of Marchetti (1999) - The Flat Dilatometer (DMT) and It's Applications to Geotechnical Design

ELASTIC SETTLEMENT OF SOIL - DMT

Uses Direct Measurement of Soil to

Calculate Settlement

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 21 of 25

ELASTIC SETTLEMENT OF SOIL - DMT

Stress Distribution

Figure courtesy of Marchetti (1999) - The Flat Dilatometer (DMT) and It's Applications to Geotechnical Design

Where: Se = Elastic Settlement !% = Change in Stress MDMT = Constrained Modulus Z = Depth

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 22 of 25

ELASTIC SETTLEMENT OF SOIL - DMT

Marchetti (1999) - The Flat Dilatometer (DMT) and It's Applications to Geotechnical Design

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 23 of 25 Figure from Hayes (1990)

ELASTIC SETTLEMENT OF SOIL - DMT

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 24 of 25

DMT SETTLEMENT EXAMPLE (NTS)

Depth (ft)

0

10.2 GWT 10 ft

Silty Sand (SM) 't = 115 pcf, (' = 34

3ft Sq. Column Q = 27 kips

Df = 1ft Df = 1ft

2ft x 4.5 ft Column Footing Q = 27 kips

Determine Settlement of Both Footings using the provided

DMT Data

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CIVL410 Geotechnical Engineering II Shallow Foundations

Slide 25 of 25

DMT SETTLEMENT

EXAMPLE

DMT Data