Space-time evolution rules of acoustic emission location of unloaded coal sample at different loading rates

作     者：Ai Ting Zhang Ru Liu Jianfeng Ren Li 

作者机构：State Key Laboratory of Hydraulic and Mountain River EngineeringSchool of Water Resource and HydropowerSichuan University Department of Mechanics and Engineering ScienceSichuan University 

出 版 物：《International Journal of Mining Science and Technology》 (矿业科学技术学报（英文版）)

年 卷 期：2012年第22卷第6期

页      面：847-854页

核心收录：

学科分类：081901[工学-采矿工程] 0819[工学-矿业工程] 0709[理学-地质学] 0808[工学-电气工程] 08[工学] 0818[工学-地质资源与地质工程] 0708[理学-地球物理学] 0807[工学-动力工程及工程热物理] 0815[工学-水利工程] 0813[工学-建筑学] 0814[工学-土木工程] 

主　　题：Coal Unloaded test Acoustic emission Space-time evolution Loading rate Precursory characteristics 

摘      要：By using MTS815 rock mechanics test system,a series of acoustic emission(AE) location experiments were performed under unloading confining pressure,increasing the axial stress.The AE space-time evolution regularities and energy releasing characteristics during deformation and failure process of coal of different loading rates are compared,the influence mechanism of loading rates on the microscopic crack evolution were studied,combining the AE characteristics and the macroscopic failure modes of the specimens,and the precursory characteristics of coal failure were also analyzed quantitatively.The results indicate that as the loading rate is higher,the AE activity and the main fracture will begin earlier.The destruction of coal body is mainly the function of shear strain at lower loading rate and tension strain at higher rate,and will transform from brittleness to ductility at critical velocities.When the deformation of the coal is mainly plasticity,the amplitude of the AE ringing counting rate increases largely and the AE energy curves appear an obvious step ,which can be defined as the first failure precursor point.Statics of AE information shows that the strongest AE activity begins when the axial stress level was 92-98%,which can be defined as the other failure precursor point.As the loading rate is smaller,the coal more easily reaches the latter precursor point after the first one,so attention should be aroused to prevent dynamic disaster in coal mining when the AE activity reaches the first precursor point.