Factor of safety of pile-stabilised slopes: an algorithm incorporating soil-arching effect

Abstract

The current practices of factor of safety computation of pile-stabilised slopes majorly depends on either the extension of methods for normal slopes with the pile-contribution introduced as an additional term or the finite element modelling. Extending conventional methods to analyse pile-stabilised slopes fail to capture the key mechanisms like soil arching, gradual transfer of resistance offered by the pile through the slope, change in slip surface due to introduction of piles, etc. In this paper, a new algorithm is proposed to compute the factor of safety of pile-stabilised slopes, in which, the Morgenstern-Price method is modified to incorporate the effect of pile. The resistance offered by pile is obtained using a pressure-based method which considers the soil arching effect in horizontal and vertical directions. The gradual propagation of this resistance offered by pile is incorporated through an iterative procedure unlike the conventional methods. The algorithm considers the change in slip surface due to introduction of the pile. The factor of safety values computed using the proposed algorithm were found to be in close agreement with that obtained from finite element modelling. In addition, a simple technique to determine the optimal location of stabilising piles and pile-spacing is also presented.