A comparison study between 2D and 3D slope stability analyses considering spatial soil variability

In engineering practice, the stability of a slope is often analyzed as a 2D problem assuming a plane-strain condition, which may lead to significant errors. In this paper, a comprehensive study is carried out to compare the results of 2D and 3D slope stability analyses, using the strength reduction method for deterministic analysis and the random field approach for probabilistic analysis, respectively. The results of this comparison study confirm that in the deterministic stability evaluation, the 2D analysis tends to obtain a smaller factor of safety than does its 3D counterpart. In the probabilistic evaluation that considers the spatial variability of soil properties, the 2D analysis tends to yield a larger probability of failure than its 3D counterpart. A significant feature of the 3D probabilistic slope stability analysis is the presence of multiple local failures distributed along the slope longitudinal direction. This paper provides insights regarding the degree of errors in modeling a 3D slope as a 2D problem, which can be regarded as a complement to the previous 3D slope stability analyses.