爆炸荷载对邻近巷道背爆侧裂纹的影响规律

为了探究爆炸应力波对邻近巷道背爆侧隐性裂纹的影响规律,采用爆炸加载透射式动态焦散线系统,进行了试验研究。试验结果表明:在爆炸荷载作用下,邻近巷道围岩中存在裂纹缺陷的背爆侧也成为主要扰动区,且扰动大小与裂纹距巷道距离和裂纹长度有关;当裂纹长度为5 mm,裂纹与巷道间距分别为2,3,4和5 mm时,裂纹扩展过程中动态应力强度因子变化曲线呈现相似的规律,即当裂纹与巷道贯穿后快速增大到第1峰值,然后在峰值上下持续振荡一段时间后减小到0,所不同的是,在峰值上下振荡性变化的持续时间和期间的最大值逐渐减小,最大值依次为1.651,1.572,1.419和1.346 MN/m3/2,这决定了裂纹远端的最终扩展位移对应为25.197,16.378,10.236和5.984 mm,呈逐渐减小的规律;裂纹与巷道间距的存在不仅对裂纹的扩展有一定的延迟作用,而且削弱了作用于裂纹远端的应力波能,并且这种延迟和削弱作用随裂纹与巷道间距的增大逐渐增强。

Effects of blast load on crack in back blast side of adjacent tunnel

For exploring the influence law of explosive stress wave on invisible cracks in back blast side of tunnel，the test was carried out by adopting the explosion loading transmission type dynamic caustics system.The experimental results show that，under explosion load，back blast side existing crack defects in the surrounding rock of adjacent tunnel becomes a main disturbance，and perturbation size is connected with distance between the crack and tunnel and crack length.When crack length is 5 mm and the distance between the crack and tunnel respectively is 2，3，4 and 5 mm，the curves of dynamic stress intensity factor in the process of crack propagation present similar laws，namely after the crack run through the roadway，rapid increases to the first peak，and then ranges up and down at a period of time and finally reduce to zero.The difference is that the duration of the oscillation change in the peak fluctuation and the maximum value gradually decreases，the maximum value of are 1.651，1.572，1.419 and 1.346 MN/m3/2，which determine that finally extended displacement of invisible crack far end corresponds for 25.197，16.378，10.236 and 5.984 mm，which renders as the regular of diminishing.The existence of the distance between the crack and tunnel not only has certain delay effect on the propagation of the crack，but also weakened stress wave energy reaching to crack far end，and the delay and weakened effects gradually are enhanced with the increase of distance between the crack and tunnel.