Acoustic Emission Characteristics of Graded Loading Intact and Holey Rock Samples during the Damage and Failure Process

Xiaofei Liu,Shuai Yang,Weikai Lu,Hui Xie,Xiaoran Wang,Huajie Zhang,Chong Zhang

doi:10.3390/app9081595

Abstract

Rock burst is the result of the development and extension of micro-cracks during the loading process of large-scale rock mass in underground space engineering. Dynamic monitoring results by acoustic emission (AE) can accurately perceive the inner fracture evolution of rock mass and effectively warn about its induced disasters early. By contrastive testing the AE parameters in the whole fracture process of the intact and holey rock samples under graded loading, their spatiotemporal evolution rules were analyzed in this paper, and the damage model of rock samples based on AE localization events was established to analyze the relationship between rock damage and loads. The results show that: (1) Under the condition of grading loading, AE parameter increases with the increase of axial stress and show three states, respectively, which are slow-growth, stabilization and rapid increasing; meanwhile, the damage of the sample has a cumulative effect with time. (2) The AE counts and energy are highly correlated with the fracture of the sample that the more severe the damage of the sample, the faster the crack propagation as well as the higher the acoustic emission counts and the energy amplitude. The damage state of granite sample can be accurately judged by two parameters to character the damage evolution process and fracture mechanism. (3) Compared with the intact rock sample, due to the pressure relief effect of the hole, the rock sample containing the hole takes a long time in the compaction stage and with higher load stress level. Although the AE counts and energy were lower in the damage process, the general law of their response during damage and instability process still exists.

Highlights

Underground space engineering has entered a high-speed construction period with the development of deep excavation technology, but more and more underground engineering is prone to structural instability and result in disasters due to the complex crustal stress conditions and lithological structures in the construction process [1,2]
During the micro-fracture process of granite loading, it will be accompanied by acoustic emission (AE) signals
Various changes will occur due to the unlike internal cracks under different stress levels of grading loading and each fracture corresponds to different levels of AE signals

Summary

Introduction

Underground space engineering has entered a high-speed construction period with the development of deep excavation technology, but more and more underground engineering (such as mining/tunnel engineering) is prone to structural instability and result in disasters (such as rock burst/coal bump) due to the complex crustal stress conditions and lithological structures in the construction process [1,2]. The development and the expansion process of the surrounding rock internal fissures under the complicated loading conditions of the underground space are closely related. The gestation and occurrence of rock instability disasters in deep rock engineering is fundamentally the evolution process of internal primary crack closure, new crack generation and expansion of the large-scale rock under loading. It is an effective tool for studying the material internal damage degree, fracture evolution and macroscopic cracks generation and expansion [6,7,8]. Liu et al [10] used

Results

Discussion

Conclusion