FDEM analysis of shale anisotropy and its effect on EDZ fracturing in deep buried tunnels

Download Statistics

Downloads

Downloads per month over past year

Li, Hongtao (2024). FDEM analysis of shale anisotropy and its effect on EDZ fracturing in deep buried tunnels. University of Birmingham. Ph.D.

Preview

Li2024PhD.pdf
Text - Accepted Version
Available under License All rights reserved.
Download (16MB) | Preview

Abstract

Fractures form and propagate in the excavation damage zone (EDZ) due to underground excavation, degrading the rock's mechanical properties and permeability, and resulting in excavation problems such as collapse, seepage, rock burst and large deformations. In addition to affecting the choice of excavation method and design of supporting structures in underground engineering projects, understanding the formation and evolution of the EDZ, especially its fracturing mechanism, is also an important assessment index for the design of permeability sensitive excavations (such as hydroelectric power generation stations or nuclear waste repositories). However, the study of the fracturing mechanism and fracturing conditions of the EDZ still remains as an open topic, especially under shale formation. As one of the most encountered rocks during underground construction, shale poses many geotechnical problems due to its special properties (e.g., anisotropic behaviours, creeping and self-sealing). Shale is difficult to study because of its complex mechanism response. Shale matrix strength and fracture mechanism are affected significantly by bedding planes with lower stiffness and cohesion. This research adopted the finite discrete element method (FDEM) to create anisotropic shale models in ABAQUS.

Based on FDEM laboratory-scale models, fracturing mechanics, fracturing behaviour, and brittleness of shale have been studied from a microscopic perspective with taking shale anisotropy into account. Three failure modes for shale in uniaxial compressive test have been identified, in terms of tensile splitting (T-S), bedding plane delamination (B-D) and shearing through matrix (S-M). Two novel new brittleness indices, in terms of BIf and BICD, have been proposed in this study to help researchers to assess shale frac-ability and provides an easy approach to evaluate rock brittleness based on uniaxial compression test. In addition, an empirical relationship has been proposed in this study to predict the tensile strength,

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):