Interslice force functions for computing active and passive earth force

Abstract

Recent methods to calculate the lateral earth force on a retaining wall have involved the method of slices and limit equilibrium concepts. An important issue in formulating the solution is the selection of an appropriate interslice force function (i.e., the ratio of the shear force to the normal force of vertical slices along the slip surface). This paper proposes interslice force functions that can be used to compute the active and passive earth forces in conjunction with the limit equilibrium method. An example problem involving a vertical wall with a horizontal backslope is analyzed using the general limit equilibrium (GLE) method and the proposed interslice force functions. The procedure recommended to compute the lateral earth force and the point of application of the force is outlined. The computed lateral earth forces, and the point of application, are compared with those from the classical solutions. For the active case, reasonable results were obtained when using an interslice force function that varies linearly from the starting point of the slip surface (at some distance from the wall) to the end point of the slip surface (adjacent to the wall). For the passive case, reasonable results were obtained when using an interslice force function that remains at zero from the starting point of the slip surface (at some distance from the wall) to the midpoint of the slip surface and then varies linearly from the midpoint of the slip surface to the end point of the slip surface (adjacent to the wall).