Earth Pressure at rest, Soil Mechanics | Soil Mechanics Notes- Agricultural Engineering PDF Download

Earth Pressure at rest

The earth pressure at rest per unit length at a depth of z from the ground surface is expressed as:

\[{p_0}={K_0}\,\gamma \,z\]                                                                                             (25.1)

where \[\gamma\] is the unit weight of the soil, K₀ is the coefficient of earth pressure at rest. Thus, the earth pressure is zero at the top of a retaining wall and at the base of the wall is K₀\[\gamma\] H (if H is the height of the wall). The total force per unit length at rest condition acting on a retaining wall of height H is expressed as:

                   \[{P_0}={1 \over 2}{K_0}\,\gamma \,{H^2}\]                                                                  (25.2)

The force (P₀) will act at a height of H/3 from the base of the wall.

For sand and normally consolidated clays, the value of K₀ is determined as (Jaky, 1944):

\[{K_0}=1-\sin \varphi\]                                                                                   (25.3)

where ø is the angle of friction of the soil. For over consolidated soil the K₀ is expressed as:

\[{K_0}={K_{0(nc)}}\sqrt {OCR}\]                                                                          (25.4)

where OCR is the over consolidation ratio.