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Bearing Capacity – Examples 1

In all these questions use partial factor set 'A1' + 'M1' + 'R1' from

the Tables below.

1. A shallow strip footing of breadth 3.5 m is to be founded at a depth of 

2.0 m in a soil which has the following (drained) properties ck' 12

k!"m2  # φκ ' 25$ # γ κ   1% k!"m3. &etermine the design bearing

resistance of the soil at this depth.

2. A strip tpe footing will be reuired to transmit a total design load of 

1.1 !"m (includes self*weight of foundation) in a saturated cohesi+esoil ha+ing the following (drained) properties ck' 1, k!"m2# φκ '

2-$# γ κ   1% k!"m3. &etermine the breadth of footing reuired at a

depth of 1.0 m. Assume &"/1.

3. A footing# 2.25 m suare# is located at a depth of 1.5 m in a sand

soil# the shear strength parameter φκ ' 3,$. &etermine the design

bearing resistance of the soil at this depth (a) if the water table is

well below foundation le+el and (b) if the water table is at groundsurface. he characteristic unit weight of the soil abo+e the water

table is 1, k!"m3 and the saturated unit weight is 20 k!"m3 .

. A strip footing is to be designed to carr a total design load of 2#000

k!"m at a depth of 0. m in a gra+ell sand (φ'k ' 0$). &etermine

the width of the assuming the water table ma rise to foundation

le+el. or the sand γ k.sat

  20 k!"m3 and abo+e the water table γ k.bulk

 

1 k!"m3. Assume &"/1.

5. A column is supported on a reinforced concrete pad footing 2.0 m

suare and located at a depth of .0 m in a sti4 cla (γ k.sat

  21 k!"m3

). he undrained shear strength of the cla is cu.k

  120 k!"m2.

&etermine the design load the column can transmit. Assume the

following the water table is at founding depth6 the soil abo+e the

water table is in a full saturated state# and the unit weight of the

concrete and back7ll material is eual to that of the cla remo+ed

from the e8ca+ation.

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The following should be used:

General Bearing Capacity equations (strip footing)

&rained condition Bearing Resistance/unit area (R'/A) c'!c 9 '! 9 0.5γ !γ 

:ndrained condition Bearing Resistance/unit area (R/A) (29π)cu 9

Bearing capacity factors

!c  (!*1)cotφ' 6 !  eπtanφ' tan2(5$ 9 φ'"2) 6 !γ   2(!*1)tanφ'

Shape factors

 ;ondition sc s sγ 

?ectangle

&rained

   

  

 

−−1

1

q

qq

 N 

 N  s

1 9   

   L

 B

@inφ'

1 0.3

   

   L

 B

:ndrained

19 0.2   

   L

 B 1 *

>ircle"

@uare

&rained As rectangle 1 9 @inφ' 0.

:ndrained 1.2 1 *

Depth factors

Condition dc dq dγ 

D/B ≤ 1 1 + 0.4(D/B) 1 + 2tanφ'(1-inφ')2(D/B) 1.0

D/B > 1 1 + 0.4tan-1 (D/B) 1 + 2tanφ'(1-inφ')2 tan-1(D/B) 1.0

ote: the factor tan*1(&") must be e8pressed in radians not degrees

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 Partial Factors for Soil Properties (BS EN 1997-1!""#)

 Partial $esistance Factors (BS EN 1997-1!""#)

 Partial Factors for %ctions (N% to BS EN 1997-1 !""#)

Soil Parameter

Set

M1 M2

Ang!e o" s#earing resistance$ 1.0 1.2%

&""ectie co#esion 1.0 1.2%

ndrained s#ear strengt# 1.0 1.4

eig#t Densit* 1.0 1.0

$ #is "actor a,,!ied on tanφ'

Resistance

Set

R1 R2 R3

Bearing 1.0 1.4 1.0

!iding 1.0 1.1 1.0

Action Set

A1 A2

eranent n"aourae 1.% 1.0

aoura!e 1.0 1.0

aria!e n"aoura!e 1.% 1.

aoura!e 0 0

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SOLU!O"S

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