带裂纹花岗岩试件三点弯变形演化及破裂机制

为建立岩石工程灾害精准预测预报体系,开展含预制裂纹花岗岩试件的三点弯试验,研究岩石试样变形演化及破裂机制。以声发射技术和数字散斑相关方法作为试验观测手段,通过矩张量反演方法研究岩石破裂类型。通过对岩石预制裂纹扩展长度及声发射振铃计数、能量和体积参数进行分析,研究岩石试件变形演化特征和破裂机制。研究结果表明:(1)三点弯岩石试样裂纹扩展具有明显的阶段性和不连续性,其过程为某次裂纹扩展 微裂纹静默积累-裂纹再次扩展;(2)预制裂纹扩展与不同破裂类型裂纹的声发射指标具有相关性。预制裂纹扩展时,张拉裂纹体积参数、能量和振铃计数随之出现;预制裂纹扩展前后,3种类型裂纹体积参数、能量和振铃计数随机产生;在预制裂纹长度保持稳定不变时,没有声发射信号产生;(3)裂纹扩展后到下一次裂纹扩展前,先是在贯通裂纹尖端附近随机出现各种破裂类型的裂纹,随着微裂纹的积累,贯通裂纹所主导的裂纹类型占比开始增加,直至产生新的贯通裂纹。

Deformation Evolution and Failure Mechanism of Three-Point Bending Granite Specimen with Cracks

This article focuses on the deformation evolution and fracture mechanism by conducting three-point bending tests on granite specimen with cracks. The purpose is to establish an accurate prediction system for rock engineering disasters. Experimental observation methods are acoustic emission technology and digital image correlation method. The rock fracture type is calculated by the moment tensor inversion method. The article analyzed the corresponding relationship between the opening displacement rate and the expansion rate of the rock prefabricated crack tip and the acoustic emission ringing count, energy and volume parameters of the seismic source. The results show that: (1) For the rock with prefabricated cracks, during the loading process, its crack propagation is a discontinuous process. When a crack propagates, the length of the crack remains unchanged for a certain period of time. As the loading progresses, when the deformation increases to a certain value, the crack continues to expand, and so on until the specimen is broken; (2) The pre-crack propagation is correlated with the acoustic emission indicators of different types of cracks. When the prefabricated crack propagates, the tension crack volume parameters, energy and ringing count appear; before and after the prefabricated crack propagates, the three types of crack volume parameters, energy and ringing count are randomly generated; when the prefabricated crack length remains stable, No acoustic emission signal is generated; (3) After the crack propagates and before the next crack propagates, the cracks of various crack types appear randomly near the tip of the penetrating crack. With the accumulation of microcracks, the proportion of crack types dominated by through cracks increases until new through cracks are generated.