Deformation and Failure Analyses of the Surrounding Rock Mass with an Interlayer Shear Zone in the Baihetan Underground Powerhouse

Fei Yuan,Qin Chen,An-Chi Shi,Gong-Da Lu,Wang-Bing Hong,Hai-Bo Li,Jia-Wen Zhou,Meng Wang,Cemal Ozer Yigit

doi:10.1155/2021/2988998

Abstract

In the process of underground cavern excavation, the existence of the interlayer shear zones or large faults often makes the surrounding rock tend to be unstable or even deformed. Under the influence of interlayer shear zone C2, different degrees of deformation and failure occurred in many parts during the excavation of the Baihetan left bank underground powerhouse. Based on field monitoring and numerical calculation, this paper studies the deformation and failure characteristics of the rock mass with C2 in the whole excavation process and the failure mechanisms are analyzed. The results show that C2 has poor mechanical properties. In the process of excavation, it mainly induces two failure modes: rock collapse and shear deformation, which specifically leads to rock collapses, large deformation and shotcrete cracking in the main powerhouse, and shear deformation in the omnibus bar caves. In addition, the similarities and differences between this study and other studies on the deformation and failure of surrounding rock of underground powerhouse in recent years are discussed, and the relevant treatment measures for C2 are given. The above research results can be a reference for other related studies.

Highlights

An interlayer shear zone is a poor rock mass system with a loose structure, weak mechanical properties, variable thickness, random distribution, strong extension, and high risk due to the shear motion of rock masses via tectonism, resulting in a variety of stability problems and geological hazards
Starting from the engineering characteristics of C2, this paper summarized the rock mass deformation and failure problems caused by C2 from three aspects: rock collapse, large deformation and shotcrete cracking in the main powerhouse, and shear deformation in omnibus bar caves
The mechanisms of rock collapse and shear deformation were analyzed. is research comprehensively summarized the rock mass deformation and failure problems caused by C2 during the whole excavation process and classified these problems into two types of deformation failure, namely, rock collapse and shear deformation

Summary

Introduction

An interlayer shear zone is a poor rock mass system with a loose structure, weak mechanical properties, variable thickness, random distribution, strong extension, and high risk due to the shear motion of rock masses via tectonism, resulting in a variety of stability problems and geological hazards. There is a potential threat to the overall stability of rock masses with interlayer shear zones in large underground cavern excavations [1,2,3,4,5]. Ding et al [13] analyzed the influence of interlayer shear zone on the stability of arch abutment through dam mechanics model test and finite element method. Few studies have systematically examined and analyzed geological problems caused by the interlayer shear zone during the whole excavation progress of the underground powerhouse. Taking the Baihetan left bank underground powerhouse as a case study, this paper studies the deformation and failure of a rock mass affected by the interlayer shear zone C2. Taking the Baihetan left bank underground powerhouse as a case study, this paper studies the deformation and failure of a rock mass affected by the interlayer shear zone C2. e conclusions are expected to provide a reference for the design, optimization, and construction of similar projects

Background

II III IV V VI 1 VI 2 VII1 VII2

Discussion

Shotcrete cracking

Findings

C2: Composed of mud and rock fragments with