Seismic Lateral Pressures in Soils with Cohesion

Abstract

A full‐range, elastic‐plastic solution for seismic stresses in the free field is obtained for an ideal Mohr‐Coulomb material with cohesion. In addition, the effect of uniform surface tractions are included as are both constant vertical and horizontal acceleration components. Moreover, the basic equations are general in that they include both the active and passive cases where the lateral boundaries deform in a similar fashion but move less or more in magnitude than the free field dictates. Thus, this solution can be used directly to determine the seismic lateral pressures on walls or, for the special case when no wall is needed, the critical seismic height of a vertical cut in a cohesive soil. Conversely, the equations can be used to find the critical acceleration level at which a wall with a given factor of safety will move in an earthquake. Finally, once this critical earthquake intensity level is determined, the actual incremental accumulation of displacement of a given wall can be calculated by the simple sliding‐block approach or a wall can be designed to limit the seismic displacement to an acceptable level.