1. School of Resource and Safety Engineering,China University of Mining and Technology(Beijing),Beijing　 100083,China; 2. State and Local Joint Engi- neering Laboratory for Gas Drainage & Ground Control of Deep Mines,Henan Polytechnic University,Jiaozuo　 454000,China

采用高清数码摄像机和红外热成像仪,对含中心孔洞煤体试件在局部荷载作用下的裂纹扩展规律进行系统的试验研究,研究分析煤体试件在不同加载面积作用下试件表面裂纹的萌生、扩展、贯通,直至形成宏观破坏的整个过程中表现出的特征与规律。试验结果表明:局部荷载作用下含中心孔洞煤体试件裂纹扩展是加载条件和宏观中心孔洞耦合作用结果,裂纹扩展路径受其主导作用,而由孔、裂隙系统引起的非均质性则占据从属地位;均布荷载条件下,孔洞周边形成拉、剪应力区,且裂纹由此起裂,孔洞是引起应力集中的主导因素,但随着加载面积的改变,孔洞的主导地位被颠覆,应力集中强弱顺序发生突转,起裂位置由孔洞周边转向荷载临界处;受载面积对含中心孔洞试件裂纹扩展的影响具有区域性特点,且明显集中出现于有载荷作用的区域;随局部荷载的增加,初始裂纹的尺度(裂纹宽度和长度)不断增加,且裂纹的发展方向出现明显的非平直化趋势。

Experimental tests about the crack propagation of coal specimens having a central borehole under local load were conducted with high definition video camera,infrared thermal imaging instrument and relevant software. The char- acteristics in the whole process of crack initiation,propagation,coalescence under different local loads were analyzed. The results showed that the crack propagation in the specimens was caused by the coupling effect of load conditions and macro center borehole,and the route of crack was also dominated by it. However,the anisotropism rooted in micro- pores played a subordinate role. It would cause tensile or shear stress area around the borehole under uniform load, which was a key factor for crack propagation on that conditions. Macro center borehole was the main factor to cause stress concentration,but the dominate position of it would subvert with the change of load area,and the sequence of stress concentration occurred suddenly,the position of crack initiation was turned from peripheral borehole to the criti- cal point of the load. The influence of load area on the crack propagation in the specimens having a central borehole had a regional characteristic,which occurred obviously in the region of load area. With local load increase,the scale of the initial crack(crack width and length) increase,and the crack direction showed the trend of non-straight.

国家自然科学基金资助项目(51474220)；深井瓦斯抽采与围岩控制技术国家地方联合工程实验室开放基金资助项目(G201603)；中央高校基本科研业务费资助项目(2009QZ03)；

Zhao Hongbao,Hu Guilin,Wang Feihu,et al. Quantitative analysis of crack expansion in specimens of coal having a single pre-existing hole[J]. Journal of China Coal Society,2017,42(4):860-870.