Displacement of Pile-Reinforced Slopes with a Weak Layer Subjected to Seismic Loads

Abstract

The presence of a weak layer in a slope requires special attention because it has a negative impact on slope stability. However, limited insight into the seismic stability of slopes with a weak layer exists. In this study, the seismic stability of a pile-reinforced slope with a weak thin layer is investigated. Based on the limit analysis theory, a translational failure mechanism for an earth slope is developed. The rotational rigid blocks in the previous rotational-translational failure mechanism are replaced by continuous deformation regions, which consist of a sequence ofnrigid triangles. The predicted static factor of safety and collapse mechanism in two typical examples of slopes with a weak layer compare well with the results obtained from the available literature and by using the Discontinuity Layout Optimization (DLO) technique. The lateral forces provided by the stabilizing piles are evaluated using the theory of plastic deformation. An analytical solution for estimating the critical yield acceleration coefficient for the pile-reinforced slopes is derived. Based on the proposed translational failure mechanism and the corresponding critical yield acceleration coefficient, Newmark’s analytical procedure is employed to evaluate the cumulative displacement. Considering different real earthquake acceleration records as input motion, the effect of stabilizing piles and varying the spacing of piles on the cumulative displacement of slopes with a weak layer is investigated.

Upper-Bound Multi-Rigid-Block Solutions for Seismic Performance of Slopes with a Weak Thin Layer

“…The value was slightly higher than the result from Discontinuity Layout Optimization (Zhou et al [24]) and the upper-bound solution based on the rotationaltranslational collapse mechanism (Huang et al [23]), but it was better than that of the upper-bound solution based on the translational collapse mechanism. Figure 7 shows the validation of the factor of safety between the upper-bound multi-rigid-block failure mechanism and the results obtained by Fredlund and Krahn [1] and Zhou et al [24]. Fredlund and Krahn [1] adopted Spencer's method and Janbu's rigorous method to evaluate the stability of slope B.…”

“…An elaborate effort is required as the velocity discontinuities are bent at the interface between adjacent blocks. Zhou et al [24] proposed a translational failure mechanism to examine the same issue. The rigid rotational blocks and in Huang et al 's study were replaced by continuous deformation regions and , including a sequence of rigid triangles.…”

“…The factor of safety computed by the proposed multirigid-block failure mechanism for slope A was first compared with the results obtained by Huang et al [23] and Zhou et al [24], as shown in Figure 6. The calculated factor of safety from the multi-rigid-block failure mechanism was equal to the FEM result.…”