巴西圆盘泥岩试件裂纹扩展及应变演化实验研究

为了研究准静态加载条件下岩石试件巴西劈裂裂纹扩展规律,采用MTS试验机进行准静态加载,同时用高速摄像机记录裂纹扩展过程。采用白光数字散斑处理软件对摄像机记录的照片进行处理,得到试件裂纹扩展过程中应变场的演化情况。通过实验和分析可以看出,由于端部效应及加载方式的原因,因此裂纹起裂点在底部加载部位;泥岩试件表面裂纹的平均扩展速度为252m/s;岩石的非均质性即内部微缺陷、微裂纹使得泥岩试样的开裂并不是沿着中心直径方向,而是偏离一定的角度,初始偏离角度约为17°。裂纹扩展过程可以划分为三个阶段:泥岩试件宏观变形阶段(宏观无裂纹)、宏观裂纹稳定扩展阶段、宏观裂纹动态张裂阶段。同时,在裂纹扩展过程中,表面第一主应变场、水平位移场等变化明显,在开裂部位第一主应变最大。通过对圆盘泥岩试件裂纹扩展实验研究,可为研究岩石破裂及其演化规律提供依据。

Experiment Study of Crack Propagation and Strain Evolution of Brazil Disc Mudstone Specimen

In order to study the crack propagation regulation of rock specimen Brazil splitting under the condition of quasistatic loading, MTS testing machine and high-speed camera were used for quasi-static loading and recording crack propagation process, respectively. Digital speckle correlation method (DSCM) processing software was used to deal with the recorded photos, the strain field evolution during specimen's crack propagation process was obtained. It can be seen from analysis of experimental results that the cracks initiate at the bottom loading position of specimen due to the end effect and loading ways; the crack average propagation velocity on mudstone specimen surface is 252 m/s; the cracking of mudstone specimen is not along the center diameter direction, but deviates a certain angle due to rock heterogeneity, such as internal micro defects and micro cracks. The initial deviation angle is about 17°. Crack propagation process can be divided into three stages: mudstone specimen macro deformation stage (no macro cracks); macro crack stable growth stage and macro crack dynamic rifting stage. At the same time, during crack propagation process, the first principal strain field and the horizontal displacement field on the surface change obviously, the first principal strain is maximum at the cracking position. Above experimental results can provide an evidence for further study of rock cracking and evolution.