剪切荷载条件下岩石细观破坏及声发射特性研究

Research on Microscopic Failure and Acoustic Emission Characteristics of Rock under Shear Load

采用煤岩细观剪切实验装置及PCI-2型声发射系统,开展了砂岩在不同剪切速率条件下的细观破坏与声发射特性试验,探讨岩石在剪切破坏过程中的破坏形式与声发射之间的关系。试验结果表明:在剪切荷载作用下,砂岩试件在不同加载速率条件下破坏过程中剪应力随时间变化趋势一致,随着加载速率增大,砂岩的剪切变形减小,抗剪强度降低;声发射活动伴随着整个剪切过程,剪应力峰值前声发射信号很少,剪应力峰值后声发射信号剧增,砂岩表面与内部裂纹萌生扩展几乎同步发生;加载速率为0.002 mm/min的砂岩试件累计Hit数最高,砂岩内累计损伤最多;砂岩试件在发生断裂破坏的短时间内经过内裂纹贯通形成主裂面、微凸体摩擦断裂形成最终破坏面两个过程,其中微凸体摩擦断裂所需剪应力低于使试件形成贯通主裂面所需剪应力。

Tests on microscopic failure and acoustic emission characteristics of sandstone were carried out at different shearing velocity by using meso-shear test equipment for coal and rock and PCI-2 acoustic emission system, and discussion was made on the relation between the failure form and acoustic emission in the process of shear failure of rock. The test results showed that under the action of the shear load, the change of sheafing stress of sandstone specimens at different loading rate was consistent with the time change, and with the increase of loading rate, the shear deformation of sandstone decreased and its shear strength reduced; the whole sheafing process was accompanied by the acoustic emission activity, the acoustic emission signal was rare before the shearing stress peak value and it sharply increased after the shearing stress peak value, the initiation and extension of cracks both on the sandstone＇ s surface and inside it almost simultaneously occurred; the sandstone specimen with loading rate of 0.002 mm / min had the highest accumulative Hit number and there were the most accumulative damages inside the sandstone ; in the short time period of the sandstone specimen fracture occurrence, it went through two processes of the formation of the main fracture surface by the internal crack through and the formation of the eventual fracture surface by the frictional fracture of the micro-bulges, of which the shear stress required for the frictional fracture of the micro-bulges was less than that for the formation of the through main fracture surface of the sandstone specimen.