基于声发射b值演化的脆性岩石裂纹起裂应力评价方法

Evaluation Method of Crack Initiation Stress in Brittle Rocks Based on Acoustic Emission b-Value Evolution

岩石裂纹起裂应力的识别和研究对认识脆性岩石受载变形及破坏过程具有重要意义。系统总结了现有的裂纹起裂应力确定方法(裂纹体积应变法、侧向应变法、移动点法、声发射振铃计数法)及存在的问题,并以单轴压缩条件下岩石破裂过程中声发射幅值及b值分析为基础,提出了一种基于声发射b值演化的脆性岩石裂纹起裂应力评价方法。采用GAW2000单轴刚性试验机和声发射测试仪开展了一系列变辉长岩和花岗岩的单轴加载试验,根据力学及声发射测试结果,对所提方法及现有方法进行了评价。研究结果表明:声发射b值演化法具有明确的物理机制及意义,可以方便准确地确定起裂应力大小,测定应力结果与现有方法所得结果具有一致性。通过方差分析可知,所提方法与现有方法不存在统计差异,验证了该方法测定裂纹起裂应力的可靠性。2类岩样的起裂应力均与单轴抗压强度呈正线性相关,使用所提方法确定的变辉长岩起裂应力约为单轴抗压强度的0.51倍,花岗岩起裂应力约为单轴抗压强度的0.48倍。所提方法及研究成果对于丰富岩石裂纹起裂应力测试手段和探究岩石脆性破坏机制具有一定的价值。

The identification and study of crack initiation stresses are of great importance for understanding the load de-formation and damage processes in brittle rocks.This paper systematically summarizes the existing methods for determining crack initiation stress(crack volume strain method,lateral strain method,moving point method,acoustic emission ringing counting method)and their problems,and proposes a method for evaluating crack initiation stress in brittle rocks based on the evolution of acoustic emission b-value.A series of uniaxial loading tests on meta-gabbro and granite were carried out using the GAW2000 uniaxial rigidity testing machine and acoustic emission tester,and the proposed and existing methods were evaluated based on the mechanical and acoustic emission results.The results show that the acoustic emission b-value evolution method has a clear physical mechanism and meaning,can easily and accurately determine the magnitude of the initiation stress,and the measured stress results are consistent with those obtained by the existing methods.The analysis of variance shows that there is no statistical difference between the proposed method and the existing method,which verifies the reliability of the method in de-termining the crack initiation stress.The crack initiation stresses of both rock samples were positively and linearly correlated with the uniaxial compressive strength,and the crack initiation stresses determined using the proposed method were about 0.51 times of the uniaxial compressive strength for meta-gabbro and 0.48 times of the uniaxial compressive strength for granite.The proposed method and its findings are valuable for enriching the means of rock crack initiation stress testing and exploring the mechanism of brittle rock damage.