Bearing Capacity

BEARING CAPACITY OF A SHALLOW FOOTING

document.xls:Homogeneous soil Page 1 04/08/2023:05:11:12

THEORETICAL BEARING CAPACITY OF SHALLOW FOUNDATIONS

Muni Budhu "Soil Mechanics and Foundations", John Wiley & Sons, NY, 2006 Table of Computed Bearing Capacity Factors - short side failure Contribution to Caquot andMeyerhof

Parameter Value Units Basic Rigidity Shape Inclination Base Tilt Ground Slope Embedment Groundwater Bearing Capacity

0 kPa Help N r s i b g d w

36 ° FINAL RESULTS q 37.75 1.00 1.00 1.00 1.00 1.00 1.06 1.00 1053 kPa

Relative density 75 % SHORT SIDE FAILURE 36.75

0 kPa 3466 kPa c 5.14 1.00 1.00 1.00 1.00 1.00 1.08 1.00 0 kPa

18 3439 kPa g 43.90 1.00 1.00 1.00 1.00 1.00 1.00 1.00 2386 kPa 3061 4829

18 46.0 3439 kPa 4114 5883

1.5 m 37.8

0 m Table of Computed Bearing Capacity Factors - long side failure Contribution to

st m Basic Rigidity Shape Inclination Base Tilt Ground Slope Embedment Groundwater Bearing Capacity

6.600 m Davis and Booker 43.9 N r s i b g d wSmooth (s) or rough (r) r ° Caquot and Kerisel (Vesic) 56.3 q 37.75 1.00 1.00 1.00 1.00 1.00 1.24 1.00 1267 kPa

535 kN Meyerhof 88.9

0 kN c 5.14 1.00 1.00 1.00 1.00 1.00 1.32 1.00 0 kPa

0 kNm g 43.90 1.00 1.00 1.00 1.00 1.00 1.00 1.00 2608 kPa

0.000 m 3874 kPa

0 kN

150 kNm

0.2803738318 m

18 m

0 °

Load inclined along length,L, or width,B B

0 °

0 °

0 °

25

5. Target Factor of Safety 3 -3

46.03 -71.66

Calculated QuantitiesTarget - Computed Factor of Safety -43.03

Volume of concrete in footing 0.0000.000 kN

Weight of equivalent soil 0.000 kN

27.000 kPa <==at base of footing (effective stress)

86.400 kPa <==at B/2 below base of footing (effective stress)

10000.000 -

324.884 -535.000 kN

0.000 kN

2.000 -

2.000 -

2.000 -Inclination n value to use 2.000

3439 kPa

3412 kPa

20606.920 kNMax vertical stress-short side 101.7 kPaMax vertical stress-longside 81.1 kPaFriction angle 0.6283185307 rad

0 rad0 rad0 rad0 rad

Effective width,B' 6.0392523364 mEffective length,L' 1 m

Davis and Booker expressions are the default for Ng

1. Soil PropertiesUndrained Shear strenght, su

Angle of friction, fp

Shear modulus, G Ultimate bearing capacity, qult

Bulk unit weight, gb kN/m3 Net bearing capacity, qu

Saturated unit weight, gs kN/m3 Computed Factor of Safety, FS2. Proposed Footing GeometryDepth of embedment, D Nqvalue (rough footing)Thickness, T

Footing length, L, or "d", or "s" Ng values (rough footing)Footing width, B

3. Loading ConditionsApplied Vertical Load, P

HB

MB

eL

HL

ML

eB

Depth to Groundwater Table, Dw

Inclination of load to vertical, w

Inclination of load to longitudinal axis, qBase tilt, hGround Slope, bUnit weight of concrete, gc kN/m3

Computed Factor of Safety - short side, FComputed Factor of Safety - long side, F

m3

==> Weight of footing, W

Initial effective overburden pressure, qs

Representative stress level, qr

Rigidity index, Ir

Critical rigidity index, Irc

Vertical component of load, NHorizontal component of load, T

Power for inclination factor, nB

Power for inclination factor, nL

Power for inclination factor, nq

Ultimate bearing capacity, qult

Net bearing capacity, qu

Ultimate net load, Qun

Inclination of load to vertical, bInclination of load to longitudinal axis, qBase tilt, aGround Slope, w

longitudinal axislongitudinal axis

minor axisminor axis

LL

+b+b

BB

PP

DD

D1

Budhu: Input values or letters in the yellow shaded cells.

A4

Set this value to zero for long-term condition (effective stress analysis)

D4

Budhu: <== The values in the yellow cell are input quantities <== Do not manipulate the cells in white color or other than yellow color ------------------------------------------------------------------------------------ NOTES: 1.Nq is Prandtl expression 2.The default bearing capacity is based on Ng is from Davis and Booker (1971). Bearing capacity based on Ng from Vesic and Meyerhof are calculated in cells R9 and S9.

A5

Peak friction angle in degrees. Set this value to zero for short-term condition (total stress analysis) for fine-grained soils.

A6

Set this value to zero if you want to calculate the rigidity factor using shear modulus, G. If this vale is greater that 70 the soil is practically incompressibel and the rigidity factor is set to 1

A7

Mylonite: Specify 50000 if unsure (=>Rigidity factors = 1) Spefify 0 if you want to use relative density to calculate the rigidity factor

A11

This value will be used to calculate the weight of the footing. You can set this value to zero if you do not know the thickness of the footing.

A12

budhu: 'Input a length value or d=circle, s=square, st= strip footing.

A13

Mylonite: Note: B must be less than (or equal to) L

A16

The horizontal load in the direction of the width , B, (you would see this force in a free body diagram showing B in elevation)

A17

The moment is applied in the long direction of the footing, MB is about the B-axis (this moment would be seen in a free body diagram showing the dimension L in elevation).

A18

The eccentricity of the footing in the direction of the length, L, due to a moment about the axis of the width.

A19

The horizontal load in the direction of the length (you would see this force in a free body diagram showing length in elevation)

A20

The moment is applied in the short direction of the footing, ML is about the axis of the length, L, (this moment would be seen in a free body diagram showing the dimension of the width in elevation).

A21

The eccentricity of the footing in the direction of the width due to a moment about the axis along the length

A22

Measured from the ground surface

A24

If the load is inclined along the length, insert L; if along the width, insert B

A25

If the load is inclined in the direction of the length, L, set this value to zero. If the load is is inclined in the direction of the width,B , set this value to 90.

K30

Budhu: *projection of down ward load vector on B,L plane * the b + ve in anticlock wise direction,when measured from load vector towards longer axis.

A40

If the relative density is > 70 %, this value is set to 10000, so that the riigity factor becomes 1

FOS

Page 2

1.65322917

BEARING CAPACITY OF SHALLOW FOOTINGS USING SPT DATA Muni Budhu "Foundation Engineering", John Wiley & Sons, NY, 2006

Eq (A)/FS Eq (B) Help

1033 1102 kPa

25 1

Width of footing 2 m 0

Depth of footing 0.9 m 1.00

Length of footing 2 m 0.014

Groundwater 5 m 1.70 mFS 3 Ho 3.3 m

Variation in N 0 1Consider ground water No

Depth Unit weight Vertical N

effective stress Calc. use

(m) (kPa)0 0 0 0 0 0 0

0.6 18.5 11.1 2.9 2.0 25 500.9 19 16.8 2.4 2.0 28 56 footing base1.2 20 22.8 2.0 2.0 33 66 1.5 19 28.5 1.8 1.8 29 53 2.1 19 39.9 1.5 1.5 28 43 2.7 19 51.3 1.4 1.4 29 40 3 20 57.3 1.3 1.3 31 40

3.3 20.5 63.45 1.2 1.2 35 43 4.2 20.5 81.9 1.1 1.1 41 44

Avg 31 48

qa

ra Cw1

Cw2

fs

Ic

z1

f1

Cn Cn N1

kN/m3

F3

Muni Budhu: Insert input values in the cells highlighted by the yellow color

B11

Muni Budhu: Set 0 if N increases with depth or is constant, else set 1

B12

Muniram Budhu: If you want to include grounwater effects, select Yes else select No.

Eq (A) AASHTO (1998)

Eq (B) Burland and Burbridge (1985)

footing base

fult 60 w1 w 2

Dq 32N B C C

B +

a 0.7s 1 c

qf f B I

r

NoYes

BEARING CAPACITY AND SETTLEMENTOF SHALLOW FOOTINGS USING CPT DATA Muni Budhu "Foundation Engineering", John Wiley & Sons, NY, 2006Condition 1 Axisymmetric HELPSettlement 26.3 mmBearing capacity 7.7 MPa

q 217 kPa 0.96

1 m 1.20

g 17

200 kPaB 3 mL 3 m

0.780056t 1 yr

Layer z z/B

m m m MPa MPa.m

01 0.20 0.20 0.07 0.19 8.40 0.005 1.682 2.90 2.70 0.97 0.54 6.30 0.230 17.013 4.60 1.70 1.53 0.24 8.00 0.052 13.604 6.00 1.40 2.00 0.00 10.10 0.000 14.14

Sum 0.286 46.43

cD

Df ct

kN/m3

snet

Icp

Dz Ico qc (Ico/qc)Dz qcDz

0 2 4 6 8 10 12

0

2

4

6

8

10

12

Influence factor

Ax-isym-metricplane strain

z/B

B3

Muniram Budhu: Select 1 = axisymmetric 2 = plane strain

F3

Muniram Budhu: 1. Insert your data in the yellow shaded cells. 2. Condition 1 is axisymmetric ( L = B) Condition 2 is plane strain (L > 10B, Strip footing)

B15

Muniram Budhu: z is the depth to the center of the layer

0 2 4 6 8 10 12

0

2

4

6

8

10

12

Influence factor

Ax-isym-metricplane strain

z/B

12

Documents

Bearing Capacity