Investigation of thermal-induced damage in fractured rock mass by coupled FEM-DEM method
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ORIGINAL PAPER
Investigation of thermal-induced damage in fractured rock mass by coupled FEM-DEM method Zhijun Wu 1 & Yuan Zhou 1 & Lei Weng 1 & Quansheng Liu 1
&
Yang Xiao 2
Received: 10 July 2019 / Accepted: 20 April 2020 # Springer Nature Switzerland AG 2020
Abstract In this study, a 3D coupled FEM-DEM method was adopted to study the influence of thermal-induced damage on the mechanical properties of fractured rock mass. In this method, the rock matrix was discretized into bulk elements bridged by cohesive elements, and the preexisting fractures were represented by cohesive elements. The thermal-induced damage process was modeled through two parts, i.e., thermal conduction and thermal-mechanical coupling. For thermal conduction process, a proposed 3D thermal-cohesive coupled model with a fracture aperture-dependent interfacial thermal conductivity was adopted to simulate the thermal conduction across the fractures, which make it possible to more precisely predict the temperature distribution. Then, the thermal stress induced by temperature variation was coupled to perform the mechanical-failure calculation. Validation simulations indicated that the proposed model is capable of dealing with the thermal-induced damage problems. Then, the influences of fracture aperture on thermal-induced damage in highly fractured rock mass were numerically investigated by the Brazilian disc tests with multiple randomly distributed fractures. The results indicated that as the fracture aperture increases, the area of thermal-induced damage zone increases and the Brazilian tensile strength (BTS) decreases nonlinearly. Keywords Thermal-induced damage . Fractured rock mass . 3D coupled FEM-DEM method . Transient thermal conduction . Thermal-cohesive coupled model
1 Introduction Thermal-induced damage in fractured rock mass is a nonnegligible problem which may be encountered in many underground engineering, for instance, exploitation of oil and deposition of nuclear waste [1]. The change in temperature under the external or internal constraints may lead to uncoordinated deformation, resulting in excessive thermal stresses. Once the corresponding induced thermal stress exceeds the strength of rocks, micro-fractures will be produced. The micro-fractures grow and coalesce with one another, forming one or more dominant macro-fractures, which may lead to the eventual failure of rock structures [2]. Therefore, it is of great
* Quansheng Liu [email protected] 1
School of Civil Engineering, Wuhan University, Wuhan 430072, China
2
School of Civil Engineering, Chongqing University, Chongqing 400044, China
importance to investigate the thermal-induced damage mechanism for rock mechanics and engineering applications. Many experimental tests have been conducted to study the effects of thermal-induced damage on mechanical behaviors of rock mass [3–11]. However, due to the limitation of the present monitoring methods, it is difficult to accurately capture the progressive micro-fracturing process of fractured rock mass. In addition, laboratory
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