Three-dimensional finite element analysis for soil slopes stabilization using piles

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Three-dimensional finite element analysis for soil slopes stabilization using piles

I-Hsuan Ho

ABSTRACT
This paper presents the analytical methods of slope-stabilising piles using the three-dimensional
(3-D) finite element (FE) analysis with the strength reduction method (SRM). This 3-D
FE model is employed to overcome the limitations observed in two-dimensional (2-D) FE
analysis. The solutions obtained from 3-D FE analyses are verified to be less conservative in
this paper. The 3-D analysis is considered to be of particular importance to pile-slope
problems. The soil that flows between piles cannot be taken account properly in the 2-D
FE analysis. The method adopted in this paper can avoid the assumption of soil movement
and the pressure distribution along the piles subjected to soil movement. The numerical
analysis employs the Mohr–Coulomb failure criterion with the strength reduction technique
for soil and an elastic member for piles. The spacing effect of the pile is considered in the 3-
D model, the S/D (S: centre to centre, ? diameter of pile) ratio, equal to 4.0, is found to be
equivalent to the single pile stabilisation. The middle portion of the slope is identified as
the optimal location to place the piles. The proper length of the pile, which can be used to
stabilise the slope, is also examined using 3-D FE analyses. It is concluded that L/H greater
or equal 0.70 is recommended (L: pile length, H: slope height). The numerical analyses are
conducted based on a coupled analysis, which simultaneously considers both the slope
stability and the pile response. The failure mechanisms of the pile-slope system subjected to
the pile locations, pile head conditions and pile length are each discussed. The contact
pressure, shear force and moment along the piles are presented to illustrate the pile
stabilising mechanism herein.

 

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