An Improved Method of Vertical Slices to Determine Seismic Passive Earth Pressure and Its Point of Application

Abstract

This paper presents a new approach for calculating seismic passive earth pressure, its point of application, and the approximate stress-state within the rupture wedge. The method of vertical slices combined with the limit-equilibrium (LE) technique was used as the framework for the analysis. While the available LE analyses used the rupture surface of predefined shapes, in this approach, the rupture surface is derived through the analysis. First, the mobilized soil behind the wall was split into thin vertical slices and the rupture plane of every slice was calculated by enforcing the Mohr–Coulomb failure criterion. Thereafter, by adding those rupture planes consecutively, starting from the wall toe, the passive rupture surface was achieved. The inclination of the rupture planes is guided by the soil friction angle, wall friction angle, seismic acceleration, and slice-interface friction angle. The distribution of slice-interface friction angle across the rupture plane was presumed to obey a power function. The exponent of the power function, the seismic passive earth pressure, and its point of application were derived concurrently by satisfying the static equilibrium conditions of the slices and applying a boundary condition. The results show that the outline of the rupture surface is guided by the slice-interface friction angle, and the shape is curvilinear for rough walls. With increasing seismic acceleration, the passive pressure decreases, and the point of application moves predominantly downward for loose sands. The obtained results were compared with those of previous numerical and experimental studies and were found to show good agreement, thus demonstrating the validity of the proposed method.