1. Session 11 – 12 LATERAL EARTH PRESSURE
Course : S0484/Foundation Engineering
Year : 2007
Version : 1/0
Session 11 – 12 LATERAL EARTH PRESSURE

2. LATERAL EARTH PRESSURE
Topic:
General
Active earth pressure
Rankine earth pressure
Coulomb earth pressure
Lateral earth pressure due to surcharge
Passive earth pressure
Influence of ground water table

3. Caused by soil self weight and or external load 3 categories:
GENERAL
Lateral earth pressure represents pressures that are “to the side” (horizontal) rather than vertical.
Caused by soil self weight and or external load
3 categories:
At rest earth pressure
Active earth pressure
Passive earth pressure

4. AT REST EARTH PRESSURE
The at rest pressure develops when the wall experiences no lateral movement. This typically occurs when the wall is restrained from movement such as a basement wall that is supported at the bottom by a slab and at the top by a floor framing system prior to placing soil backfill against the wall.

5. ACTIVE EARTH PRESSURE
The active pressure develops when the wall is free to move outward such as a typical retaining wall and the soil mass stretches sufficiently to mobilize its shear strength.

6. PASSIVE EARTH PRESSURE
If the wall moves into the soil, then the soil mass is compressed
sufficiently to mobilize its shear strength and the passive pressure develops.

7. AT REST EARTH PRESSURE Jaky, Broker and Ireland  Ko = M – sin ’q
Jaky, Broker and Ireland  Ko = M – sin ’
Sand, normally consolidated clay  M = 1
Clay with OCR > 2  M = 0.95 z
v =  . z + q
Broker and Ireland
Ko = PI , 0  PI  40
Ko = PI , 40  PI  80 v h
Sherif and Ishibashi  Ko =  +  (OCR – 1)
 = (LL – 20)
= (LL – 20)
LL > 110%   = 1.0 ;  = 0.19
At rest, K = Ko

8. ACTIVE EARTH PRESSURE

9. ACTIVE EARTH PRESSURE RANKINE ACTIVE EARTH PRESSURE
1 = 3 . tan2 (45+/2)+2c.tan (45+/2)
a = v . tan2(45-/2) – 2c . tan (45-/2)
a = v . Ka – 2cKa
Ka = tan2 (45 - /2)

10. Note : z = 0  v = 0 ; a = -2cKa z = H  v = H
ACTIVE EARTH PRESSURE
Note :
z = 0  v = 0 ; a = -2cKa
z = H  v = H
The tensile stress decreases with depth and becomes zero at a depth z = zc or
zcKa – 2cKa = 0
and
zc = depth of tensile crack

11. ACTIVE EARTH PRESSURE
RANKINE ACTIVE EARTH PRESSURE FOR INCLINED BACKFILL
(for granular soil, c = 0)
For c- soil

12. ACTIVE EARTH PRESSURE COULOMB ACTIVE EARTH PRESSURE Pa = ½ Ka .  . H2
Assumptions:
Fill material is granular soil
Friction of wall and fill material is considered
Soil failure shape is plane (BC1, BC2 …)
Pa = ½ Ka .  . H2

13. ACTIVE EARTH PRESSURE
COULOMB’S ACTIVE EARTH PRESSURE WITH A SURCHARGE ON THE BACKFILL

14. PASSIVE EARTH PRESSURE
RANKINE PASSIVE EARTH PRESSURE

15. PASSIVE EARTH PRESSURE
RANKINE PASSIVE EARTH PRESSURE
p= v . tan2(45+/2) + 2c . tan (45+/2)

16. PASSIVE EARTH PRESSURE
RANKINE PASSIVE EARTH PRESSURE
Kp = tan2 (45 + /2)
h = v . Kp + 2cKp

17. PASSIVE EARTH PRESSURE
COULOMB PASSIVE EARTH PRESSURE
Pp = ½ Kp .  . H2

18. LATERAL EARTH PRESSURE DUE TO SURCHARGE

19. LATERAL EARTH PRESSURE DUE TO SURCHARGE

20. PURPOSE OF LATERAL EARTH PRESSURE
STABILITY ANALYSIS GRAVITY WALL AGAINST
SLIDING
OVERTURNING

21. PURPOSE OF LATERAL EARTH PRESSURE

22. PURPOSE OF LATERAL EARTH PRESSURE