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Lateral Earth Pressure for at Rest Condition

If the wall is rigid and does not move with the pressure exerted on the wall, the soil behind the wall will be in a state of elastic equilibrium. Consider a prismatic element E in the backfill at depth z shown in Fig. 11.5.
Element E is subjected to the following pressures.
Vertical pressure - lateral pressure
 
Figure 11.3 Wall movement for the development of active and passive earth pressure
 
Lateral Earth Pressure for at Rest Condition
 
Figure 11.5 Lateral earth pressure for at rest condition
The expression for oh at depth H, the height of the wall, is
Lateral Earth Pressure for at Rest Condition
 
Table 11.1 Coefficients of earth pressure for at rest condition
 
The value of KQ depends upon the relative density of the sand and the process by which the deposit was formed. If this process does not involve artificial tamping the value of KQ ranges from about 0.40 for loose sand to 0.6 for dense sand. Tamping the layers may increase it to 0.8. The value of KQ may also be obtained on the basis of elastic theory. If a cylindrical sample of soil is acted upon by vertical stress CT, and horizontal stress ah, the lateral strain e{ may be expressed as
Lateral Earth Pressure for at Rest Condition eq