A Case Study of Two Failures of a High Cut-slope in the Northeastern Area of Sichuan, China

Abstract A high cut-slope in the northeast of Sichuan Province, China failed after excavation followed by rainfall. A second slope failure occurred under heavy rainfall a few days after being reinforced with anchor cables and grid beams. In this study, the detailed information and the failure history of the cut-slope were first presented. A series of numerical simulations were then conducted using finite element method (FEM) to analyze the slope stability and explore the failure mechanism. The numerical analyses found that the slope failures should not be simply attributed to rainfall. Other lessons have been learned from these two failures. They are: mis-characterization of the geological and hydraulic conditions of the site, poor understanding of the reaction of strongly weathered argillaceous shale materials with weak interlayers to water, and failing to implement proper drainage system in the slope after placing shotcrete on the slope surface. These resulted in the wrong measures to protect the cut-slope and the improper remediation works to stabilize the failed slope. The bond section of the anchor cable should be installed in the moderately weathered rock layer rather than strongly weathered layer with weak planes. The multiple failures of the slope warned all the parties that proper understanding of the geological and hydrological conditions of the site and the material properties is the starting point of any design and construction works.