7.2. Coulomb Theory (1776)

Active Earth Pressures

where:

Passive Earth Pressures

where:

For the Passive Case, the Coulomb Theory cannot be used when δ > 2/3φ because in this case the failure surface is highly curved. Figure 7.2 gives values of K_P for different values of φ and δ, for a curved failure surface.

Calculation of Earth Pressures below the water table

In this case, the earth pressures are estimated by superposition of the following two resultants:

1. Earth pressures do to effective stresses in the soil (using the effective unit weights)
2. Earth pressure due to the hydrostatic stresses of the water