局部荷载下含孔洞多孔介质裂纹扩展量化分析

Quantitative analysis of crack propagation in specimens of porous media having a borehole under local load

采用高清数码摄像机和红外热成像仪对局部荷载作用下含中心孔洞多孔介质试件的裂纹扩展规律进行了较系统的试验研究和理论分析.试验结果表明:局部荷载作用下含中心孔洞多孔介质试件裂纹扩展是加载条件和宏观中心孔洞耦合作用的结果,裂纹扩展路径受其主导作用,而由天然细观孔洞引起的非均质性的影响作用则占据从属地位;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,形成的裂纹也均出现在载荷作用范围内的区域;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,试件受到的局部加载效应越显著,裂纹尺度变化的越快、发展方向变化的越剧烈.

Experimental tests and theoretical analysis on crack propagation of porous media under local load were done with high definition digital camera and infrared thermography.The results show that the crack propagation in porous media results from the coupling effect of load conditions and macro-central borehole.They play a leading role in the path of crack propagation,while the heterogeneity caused by natural micro-pores play a subordinate role.It will develop tensile and shear stress area around the borehole under uniform load,which is a key area for crack propagation on that condition.Macro-central borehole is the main factor for stress concentration,but the dominate position of it will be subverted with the change of load area,and the intensity sequence of stress concentration changes suddenly,the crack initiation moves from the area around the borehole to the critical area of the load,and crack propagation also appears in the load area.With local load increasing,the scale of the initial crack（its width and length）is increasing,and the crack direction shows the trend of non-straight.The greater the local load,the faster the development of crack scale and the more dramatic the development ofcracks direction.