Analysis of Clay Slopes with Piles Using 2D and 3D FEM
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TECHNICAL NOTE
Analysis of Clay Slopes with Piles Using 2D and 3D FEM Mohamed Sobhey
. Marawan Shahien . Mostafa El Sawwaf . Ahmed Farouk
Received: 24 October 2019 / Accepted: 29 October 2020 Ó Springer Nature Switzerland AG 2020
Abstract The aim of this paper is to compare between results of the 2D finite element method (FEM) and results of the 3D (FEM) when they are used to assess the factor of safety of clay slopes stabilized with vertical piles. It is expected that this comparison will aid engineers to judge and convert the results of the simplified 2D analysis to the more realistic results of the sophisticated 3D analysis that simulates the real behavior of slopes having infinite length. Extensive numerical modelling of homogeneous clay slopes stabilized with a row of piles and underlined by a bed of rock are carried out using the PLAXIS 2D program (version 8.2) and the PLAXIS 3D program (version 2010), which are both based on the shear strength reduction method to evaluate the factor of safety of the slope. The increase in factor of safety (FSI) of the stabilized clay slope is investigated considering many parameters, which include, the slope width, location of the piles, piles diameter, piles spacing and shear
M. Sobhey (&) M. Shahien M. El Sawwaf A. Farouk Structural Engineering Department, Tanta University, Tanta, Egypt e-mail: [email protected] M. Shahien e-mail: [email protected] M. El Sawwaf e-mail: [email protected] A. Farouk e-mail: [email protected]
strength of the clay. Results of both PLAXIS programs are presented and compared in terms of increase in the FSI % relative to cases of slopes without stabilizing piles. Keywords Clay slopes Piles 2D and 3D (finite element method) Factor of safety
1 Introduction The soil mass movement during landslides might cause destruction to human life along its path, and hence, there is always a need to increase the stability of such movement, which includes the sliding of slopes. One of the most common ways to stabilize unsafe slopes is to use a row of piles along the slope length. When a row of piles is used to increase the stability of a slope, it will be subjected to lateral pressures due to soil mass movement above the slip surface. Previous studies, e.g., Ito et al. (1975), De Beer and Carpentier (1977), Poulos, (1999), Yang et al. (2011), Sobhey et al. (2017) and Hajiazizia et al. (2018); reported that increasing the embedment depth of a row of piles below the slip surface of a slope raises the passive resistance pressure, which, in turn, results in an equilibrant state with the lateral pressure acting on the piles due to the sliding soil mass as shown in Fig. 1. In fact, the passive pressure resultant (Rf)
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Fig. 1 A scheme illustrates the lateral pressure acting on row of piles in a clay slope (Data from Poulos 1999)
provides stability to the slope along its slip surface and reduces the excessive soil mass movement. Nowadays, man
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