Toppling deformation characteristics and mechanism of bank slope in Xiluodu Hydropower Station, China

Abstract

Xiluodu Hydropower Station of the Jinsha River started impounding water in May 2013. In June 2013, five cracks occurred on the bank slope of the Xingguang village. By the end of 2019, the number of slope cracks has increased to 13. Based on the detailed field investigation, deformation monitoring, and drilling and adit investigation, the deformation characteristics of the Xingguang bank slope are studied. The results indicate that the Xingguang bank slope is a steep bedding toppling deformation, which is further intensified by the impoundment operation of the reservoir. Monitoring data show that the Xingguang bank slope does not deform toward the free direction, but inclines upstream, and the deformation gradually increases from the top to bottom. According to the change degree of slope surface displacement, the Xingguang bank slope can be divided into four deformation areas in the plane: intensified strong deformation area, strong deformation area, moderate deformation area, and slight deformation area. Based on the deformation degree of the rock mass, the vertical section is divided into four deformation zones: intensified strong toppling deformation zone, strong toppling deformation zone, moderate toppling deformation zone, and slight toppling deformation zone. Further study reveals that the thin-layer rock mass structure is the material basis of the bank slope toppling deformation, the landform formed by the cutting of the Jinsha River Valley provides favorable boundary conditions for the toppling deformation, and the strong unloading rebound of the rock mass is the key factor of the bank slope toppling deformation.