The Islamic university - Gaza

Faculty of Engineering

Civil Engineering Department

Principles of foundation Engineering

Chapter 7 Lateral earth pressure

Engr. Safaa Abu El-Aish

Types of lateral earth pressure:•At rest soil pressure:

•Active soil pressure:

•Passive soil pressure:

h

)( ' qk voh

ok sin1ok

uqk voh )( '

HkP

HqkP

ov

o

'02

01

2

1

At rest soil pressure:

At any distance (z) below the ground surface, the lateral earth pressure ( )equals:

:At rest pressure coefficient, For normally consolidated

If there is water table we have to add the effect of water pressure to the lateral pressure:

The coefficient of lateral earth pressure for the water =1 for any case.To find the at rest forces:

ww h

2

2

1www hP

•The water stress diagram is a triangle starts from (0.00) to the value of

•Rankin Active soil pressure:

a

c

a

k

cZstresstensileofDepth

kcstressTensile

2

2

aava kck 2'

2

45tan 2ak

Ranking passive soil pressure:

ppvp kck 2' a

p kk

1

245tan 2

Note:

For retaining wall design, the active soil pressure is assumed as follow (Modified Active

soil pressure)

EXAMPLE 1:

Example(

A 3m length wall as shown below, Determine the ranking passive soil pressure

per unit length of the wall.

2

2

2'

2

2'

22'

'

2222

2121

/81.9181.9

/654.13556.210256.249.40

/49.4081.986.18172.1523

/4.11256.210244.3156.2

/44.3172.152r tableafter wateJust 2

/32.9444.313/44.3172.152r tablebefor wateJust 2

00.00

56.22

2645tan

245tan

32

3045tan

245tan

mKNu

mKN

mKNhfor

mKN

mKNmhfor

mKNmKNmhfor

hfor

k

k

h

v

h

v

hv

v

p

p

KNP

KNP

KNP

KNP

p

p

p

p

905.4181.92

1

625.1114.11265.1352

1

4.11214.112

32.9432.9422

1

4

3

2

1

00.0c

HP

Hk

k

aa

aa

a

2

1

coscoscos

coscoscoscos

22

22

HP

Hk

k

pp

pp

p

2

1

coscoscos

coscoscoscos

22

22

•Rankin soil pressure for inclined backfill:

Passive:

Active:

z

c , , offunction , table toGo , find To

sin1

sin12

2

1

cos

'

'

a

c

aa

aa

k

cZ

hP

zk

z

c , , offunction , table toGo , find To

2

1

cos

'

'

p

pp

pp

k

HP

zkPassive:

Active:

soil c

THE END