Different Theories of Earth Pressure

There are two classical theories of earth pressure. They are

Coulomb's earth pressure theory.

Rankine's earth pressure theory.

Coulomb published the first rigorous analysis of lateral earth pressure problem in 1776. Rankine proposed a different approach to the problem in 1857. These theories propose to estimate the magnitudes of two pressures called Active earth pressure and Passive earth pressure . All the theories proposed by Coulomb have been discussed in the later part of the chapter.

Assumptions

Most of the theories of earth pressure are based on the following assumptions: the backfill of the wall is isotropic and homogenous; the deformation of the backfill occurs exclusively parallel to the vertical plane at right angles at the back of the wall, and the neutral stresses in the backfill material are negligible.

The soil mass is semi infinite, homogeneous, dry & cohesion less.

The ground surface is plane which may be horizontal or inclined.

The back of the wall is smooth & vertical. In other words, there are no shearing stresses or frictional stresses between the wall & the soil. The stress relationship for any element adjacent to the wall is the same as for any other element farther away from the wall.

The soil mass is in a state of plastic equilibrium i.e. at the verge of failure.