Mechanical Behavior and Damage Evolution for Granite Subjected to Cyclic Loading

Zhiliang Wang,Jingbin Zheng,Peng Gao,Jikang Yao,Nuocheng Tian

doi:10.1155/2018/4312494

Zhiliang Wang, Jingbin Zheng + Show 3 more

Open Access

https://doi.org/10.1155/2018/4312494

Copy DOI

Abstract

This paper focuses on the mechanical behavior and damage evolution of Huashan granite subjected to cyclic loading. Four levels of confining pressure (0, 15, 25, and 35 MPa) were applied during cyclic axial loading by using a Rock Test System (MTS815) along with an acoustic emission (AE) monitoring device. Experimental results indicate that the number of AE activities is higher under cyclic triaxial loading compared to that under cyclic uniaxial loading. The measured stress-strain curves of both uniaxial and triaxial tests under cyclic loading are concave-up, but the degree of concavity is mild for the latter. As the cycle number rises, elastic modulus of the granite sample under different confining pressures increases. The slope of the peak strength versus confining pressure plot for the cyclic loading is larger than that for the monotonic loading. Besides, it is found that the dissipated energy increases with the increase of cyclic stress, but it hardly increases in proportion with the confining pressure. The damage parameters defined in terms of the plastic strain can be extended for the whole cyclic loading process, and they agree well with the energy-based damage parameters.

Highlights

In geotechnical engineering practices such as tunnel excavation and support, shale gas mining, and safe disposal of nuclear waste, rock material is subjected to different loading conditions
Wang et al [7] investigated the hydromechanical behavior of granite subjected to cyclic loading under triaxial compression conditions and revealed that the stress corresponding to the transition from volumetric compaction to volumetric dilation might be taken as the threshold for fatigue failure
E remainder of the paper is organized as follows: (i) the acoustic emission (AE) activities are compared between the samples under cyclic uniaxial and cyclic triaxial loading; (ii) the effect of confining pressure on the cyclic mechanical behaviors of the samples is analyzed; (iii) the characteristics of energy dissipation of the samples under cyclic loading are explored; and (iv) the damage of the samples subjected to cyclic loading under triaxial compressive conditions is evaluated from the perspectives of energy dissipation and plastic strain, respectively, based on which damage parameters are defined and discussed

Summary

Introduction

In geotechnical engineering practices such as tunnel excavation and support, shale gas mining, and safe disposal of nuclear waste, rock material is subjected to different loading conditions (including triaxial versus uniaxial or cyclic versus monotonic). E main objective is to present the AE characteristics and mechanical behaviors of the granite sample under cyclic loading and unloading Key issues such as the energy dissipation, the evolution of microcracks, and the damage definition of the granite rock are discussed. E remainder of the paper is organized as follows: (i) the AE activities are compared between the samples under cyclic uniaxial and cyclic triaxial loading; (ii) the effect of confining pressure on the cyclic mechanical behaviors of the samples is analyzed; (iii) the characteristics of energy dissipation of the samples under cyclic loading are explored; and (iv) the damage of the samples subjected to cyclic loading under triaxial compressive conditions is evaluated from the perspectives of energy dissipation and plastic strain, respectively, based on which damage parameters are defined and discussed

Equipment and Test Scheme

Experimental Results

Characteristic of Mechanical Behavior

Evaluation of Rock Damage

Conclusions