A Coulomb-type solution for active earth thrust with seepage

A Coulomb-type general solution for active earth pressure on the vertical face of a retaining wall with a drainage system along the soil-structure interface is presented. The soil is cohesionless and fully saturated to the ground horizontal surface. This condition may happen during heavy rainfall and is the most critical, when the active pressure reaches its peak value. In order to solve the problem, a theoretical, closed-form solution for the water seepage through the soil is first developed. This is used in a Coulomb-type formulation, which supposes a plane failure surface inside the backfill when the wall movement is enough to put the soil mass in the active state. The formulation provides Coulomb-like coefficients of active pressure, which solve the problem in a generic way. Comparison with published results obtained by hand calculation shows very good agreement. A table with values of the coefficients of active earth pressure with seepage calculated for selected values of the soil internal friction angle and of the wall-soil friction angle is presented.