The Islamic university - GazaFaculty 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
21
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
21
www hP
•The water stress diagram is a triangle starts from (0.00) to the value of
•Rankin Active soil pressure:
ac
a
kcZstresstensileofDepth
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
2645tan2
45tan
32
3045tan2
45tan
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
905.4181.921
625.1114.11265.13521
4.11214.112
32.9432.94221
4
3
2
1
00.0c
HP
Hk
k
aa
aa
a
21
coscoscos
coscoscoscos22
22
HP
Hk
k
pp
pp
p
21
coscoscos
coscoscoscos22
22
•Rankin soil pressure for inclined backfill:
Passive:
Active:
zc , , offunction , table toGo , find To
sin1sin12
21
cos
'
'
a
c
aa
aa
k
cZ
hP
zk
zc , , offunction , table toGo , find To
21
cos
'
'
p
pp
pp
k
HP
zkPassive:
Active:soil c
THE END