动静荷载下巷道围岩倾斜裂纹的动焦散试验

Dynamic caustics test on the inclined cracks in roadway surrounding rock subjected to static-dynamic load

利用爆炸加载动态焦散线测试系统,采用PMMA材料加工模型试件,进行裂纹扩展规律的动焦散试验研究。结果表明:预制裂纹b端在应力波作用下起裂,扩展轨迹出现翘曲变化的现象,大体上沿水平方向扩展;裂纹b端扩展位移随倾角θ呈现增大和减小交替变化的规律,在-45°~45°内,扩展位移曲线大体上关于直线θ=0°对称,在-75°^-45°和45°~75°内,位移曲线呈现较大差别;扩展位移曲线在θ=-45°,θ=0°和θ=60°处达到峰值,分别为22,31,36 mm,在θ=±30°处达到低谷值9 mm和11 mm;应力强度因子KⅠd变化曲线和能量释放率G变化曲线具有相似的变化规律,均先达到峰值,后反复振荡变化、多次出现峰值;KⅠd值和G值与能量紧密相关,当两者的数值相对较大时,相应裂纹扩展位移较大,反之,裂纹扩展位移较小。

The transmitted caustics experimental system has been used to conduct the dynamic caustics research about the propagation law of cracks and the poly methyl methacrylate（PMMA） plates have been employed to make model specimens. The results have shown that： 1） All the b endpoints of the prefabricating cracks propagate under the action of the stress wave and generally extend along the horizontal direction with a phenomenon of warping seen from the propagation path; 2） As the dip angle θ changes, the extension displacement of b endpoint has the rule of variation between increasing and decreasing, and the extension displacement curve is generally symmetrical about the linear θ=0° from-45° to 45°, but it has an apparent difference from-75° to-45° and 45° to 75°; 3） When θ=-45°, θ=0° and θ=60° the extensiondisplacement curve reaches the peak values of 22, 31 and 36 mm respectively, and reaches the low values of 9 mm and 11 mm when θ=±30°; 4） The change curve of stress intensity factor KⅠd and the change curve of energy release rate G have a similar trend, which are both at a peak value at first, then the repeated oscillation change with peak value for several times; 5） The values of stress intensity factor and energy release rate are closely related to energy, which means the displacement of corresponding crack is larger when the values both have a relatively higher level, otherwise it is small relatively.