基于DIC技术的预裂煤岩体裂隙演化特性研究

Study on cracking evolution characteristics of pre-fractured coal and rock mass based on DIC technology

为了研究煤岩体裂隙网络结构以及表面裂隙演化发展过程,开展了基于采动煤岩体应力路径的三轴加载试验,在应力刚超过峰值应力时停止加载,得到采动应力作用下的预裂煤岩体;然后引入数字图像相关(DIC)技术,并继续单轴加载,观察和记录裂隙演化发展过程;并结合分形几何,计算出不同加载阶段煤岩表面裂隙的分形维数。研究结果表明:在真实采动应力路径下,受围压释放的影响,煤岩承载能力下降超过40%;由于裂隙面的粗糙度不同以及煤岩体非均质性和原生缺陷等,预裂煤岩体除了沿预裂裂隙面继续变形破坏外,还会产生新的次生裂隙;在单轴压缩条件下,预裂煤岩体表面裂隙分形维数由1.12增长到1.60,裂隙演化的整体趋势为缓慢→快速发育→平稳。

In order to study the cracking network structure and the surface cracking evolution development process of the coal and rock mass,a triaxial loading test was conducted based on the mining stress path of the coal and rock mass.A loading operation was stopped when the stress was just over the peak stress and the pre-fractured coal and rock mass under the mining stress role were obtained.Then the DIC technology was introduced,an uniaxial loading was continued and the cracking evolution development process was observed and recorded.In combination with the fractal geometry,a fractal dimension of the surface cracking on the coal and rock in different loading stage was calculated.The study result showed that under the real mining stress path,with the influence of the surrounding pressure released,the loading capacity of the coal and rock was reduced over 40%.Due to the different roughness of the cracking surface and the heterogeneity and insitu defects,except for the continuous deformation and failure along the pre-fractured cracking surface,the pre-fractured coal and rock mass would occur new secondary cracking.Under the condition of the uniaxial compression,the fractal dimension of the cracking on the surface of the coal and rock mass would be increased from 1.12 to 1.60,and the completed tendency of the cracking evolution would be slow to rapid developed to steady stable.