Investigation of Stability and Failure Mechanism of Undercut Slopes by Three-Dimensional Finite Element Analysis

Slope failures along a bedding plane were critical issues and mostly happened in an open pit mining project such as the Mae Moh Mine, Thailand. The prediction of maximum width to maintain stable slope after an excavation process is required. This paper presents an investigation of 3D finite element analysis for the stability and failure mechanism of undercut slopes resting on a low interface friction plane. In numerical models, the soil slope was modeled as volume elements with the hardening soil material. Interface elements were used at the bottom plane to simulate the low interface friction plane and at the side support to simulate fully rough surface for the models with side supports. Stage analyses in numerical models were performed following excavation processes in physical models until failure. The effects of the side support and the slope length to increase the stability of undercut slopes were considered. Failure widths, failure mechanisms, and stress distributions associated with slope angles and boundary conditions of side support were discussed and compared.