Hybrid Method for Analysis and Design of Slope Stabilizing Piles

Abstract

Piles are extensively used as a means of slope stabilization. Despite the rapid advances in computing and software power, the design of such piles may still include a high degree of conservatism, stemming from the use of simplified, easy-to-apply methodologies. This paper develops a hybrid method for designing slope-stabilizing piles, combining the accuracy of rigorous three-dimensional (3D) finiteelement (FE) simulation with the simplicity of widely accepted analytical techniques. It consists of two steps: (1) evaluation of the lateral resisting force (RF) needed to increase the safety factor of the precarious slope to the desired value, and (2) estimation of the optimum pile configuration that offers the required RF for a prescribed deformation level. The first step utilizes the results of conventional slope-stability analysis. A novel approach is proposed for the second step. This consists of decoupling the slope geometry from the computation of pile lateral capacity, which allows numerical simulation of only a limited region of soil around the piles. A comprehensive validation is presented against published experimental, field, and theoretical results from fully coupled 3D nonlinear FE analyses. The proposed method provides a useful, computationally efficient tool for parametric analyses and design of slope-stabilizing piles.

Simplified Model for the Hybrid Method to Design Stabilising Piles Placed at the Toe of Slopes

“…The hybrid method for the design of slope-stabilizing piles was proposed by Kourkoulis et al in 2012. It consists of two steps; (1): an analytical estimation of the resisting force needed to stabilize the precarious slope, and (2): a numerical analysis to define the adequate pile configuration that offers the required resisting force for a desired pile head displacement.…”

“…For piles placed in the middle of precarious slopes, it was found that beyond a distance of 5D up-slope of the piles row, the soil displacement profile becomes almost uniform [12]. Therefore, 10D (2 times 5D) was chosen to be the length of the simplified model.…”

The Effect of Fixed Piles Tip on Stabilization of Earth Slopes

“…The piles are embedded in the stable soil by the length of 5D (D=pile diameter), because the zone of influence of each pile has been demonstrated not to exceed 5D and the length of the pile is restricted to 10D. Fixing pile end helps to have a pile length shorter than the length proposed by Kourkoulis [14] and diminishes stabilization costs.…”

“…Their approach presumes that the soil is soft and deforms plastically around piles. Despite its rigor, the method neglects pile flexibility, pile limited length, and soil archingphenomena that may all have a substantial effect [14]. Hassiotis et al [17] presented the friction circle method by defining new expressions for the stability number to incorporate the pile resistance in slope stability analysis using a closed form solution of the beam equation.…”

“…Kourkoulis et al [14] divided pile-based stabilization methods for earth slopes into the following two categories: (1) Displacement -or pressure-based methods [15][16][17][18][19][20], and (2) Numerical methods [17,21,22,23]. Moreover, slope stability and optimizing pile location by installing a row of piles [16,19,24,25,26,27,28] have been studied by many researchers.…”