2. What is Lateral Earth Pressure?
Lateral earth pressure is the pressure that soil
exerts in the horizontal direction.
3. Why We Study Lateral Earth
Pressure?
Lateral Earth pressure is an important parameter
for the design of bridge abutment, different types
of retaining walls (Such as gravity retaining walls,
cantilever walls, buttresses), sheet piles and other
retaining structures.
It is important because it affects the consolidation
behavior and strength of the soil also because it is
considered in the design of retaining
walls, basements, tunnels etc.
15. Lateral Earth Pressure
There are 3 states of lateral earth pressure
1. Ko= At Rest
2. Ka= Active Earth Pressure
3. Kp= Passive Earth Pressure
(Passive is more like a resistance)
16. Earth Pressure At Rest
At rest earth pressure occur when there is no wall
rotation such as in a braced wall. (for example basement wall)
17. At Rest Earth Pressure
Ko can be calculated as follows:
Ko = 1 – sin φ
18. Active Earth Pressure
Active earth pressure occurs when the wall tilts away
from the soil.
(for example a typical free standing retaining wall)
• In Active earth pressure the value of K is minimum.
19. Active Earth Pressure
Kacan be calculated asfollows:
2
45
tan2
o
a
K
sin
1
sin
1
a
K
20. Passive Earth Pressure
Passive earth pressure occurs when the
wall is pushed into the soil.
And a wall pushed into the soil when a
seismic load pushing the wall into the soil or
a foundation pushing into the soil.
In Passive earth pressure the value of K is
maximum.
21. Passive Earth Pressure
Kp can be calculated as follows:
Kp = tan2 (45 + φ/2)
sin
1
sin
1
p
K
24. WORK EXAMPLE 1
Calculate the resultant active thrust on a vertical
smooth retaining wall of height 5.4m. The water
table is well below the base of the wall.
Soil properties :
= 30, c = 0, = 20kN/m3
25. Calculate Ka using appropriate equation.
o
Calculate the lateral soil pressure, a = KaH.
Find the resultant active thrust, Pa = ½ KaH2
Determine the point of action at a height of H/3
above the base .
2
45
tan2
o
a
K
sin
1
sin
1
a
K
26. Calculate the Rankine active force per unit
length of the wall shown below, and also
determine the location of the resultant.
5m
γ=15.7kN/m3
Φ’=30
c’=0
WORK EXAMPLE 2
Ans : Pa = 65.4kN/m , y = 1.67m
27. coefficient of passive earth pressure, Kp
Lateral soil pressure, p = KpH
Resultant force per unit length of wall,
Pp = ½ KpH2
ii)
i)
2
45
tan2
o
p
K
sin
1
sin
1
p
K
28. WORK EXAMPLE 3
For the retaining wall considered below, what is
the Rankine passive force per unit length of the
wall?
5m
γ=15.7kN/m3
Φ’=30
c’=0
Ans : Pp = 588.75kN/m , y = 1.67m
29. WORK EXAMPLE 4
Determine the active force per unit length of
the wall for Rankine state. Also find the location
of the resultant. (Das, 2010)
z
GWT
γ = 16 kN/m3
Φ’ = 30
c’ = 0
γsat = 18 kN/m3
Φ’ = 30
c’ = 0
3m
3m
Ans : Pa = 128.394kN/m , y = 1.78m