节理介质断裂控制爆破裂纹扩展的动焦散试验研究

DYNAMIC CAUSTICS EXPERIMENT ON CRACK PROPAGATION OF JOINTED MEDIUM FRACTURE WITH CONTROLLED BLASTING

为研究闭合和张开节理对切缝药包断裂控制爆破裂纹扩展规律的影响和裂纹扩展机制,采用有机玻璃模型,用切缝药包形成初始裂纹,进行爆炸加载下透射式动焦散试验。试验结果表明:2种节理对裂纹扩展影响都很大,初始裂纹都没穿过节理,但在节理两端产生翼裂纹,翼裂纹基本沿原爆生裂纹方向继续扩展;在张开型节理试验中,切缝药包爆炸后25μs时节理两端出现焦散斑,2条翼裂纹最长只有2.5 cm;闭合型节理则在1μs时产生焦散斑,比张开型产生的时间早了24μs,翼裂纹最长达5.6 cm。2种试验中翼裂纹尖端复合动态应力强度因子呈由小变大再变小振荡变化的趋势,初始阶段动态应力强度因子KdII低于KdI,闭合型应力强度因子峰值为1.72 MN/m3/2,大于张开型峰值1.28 MN/m3/2。研究结果可为节理岩体定向断裂控制爆破提供理论依据。

The crack propagation mechanism and influence of closed and open jointed medium were studied on crack propagation law of cutting seam cartridge fracture with controlled blasting.Dynamic caustics experiment of blasting loading was carried out in PMMA material by forming initial cracks through cutting seam cartridge directional fracture.The experimental results show that those two kinds of jointed medium have great influence on crack propagation;and the initial cracks do not traverse joints;and wing-cracks are generated at both ends of joints and basically go on extending along original explosion crack.In open joint experiment,a caustics speckle appears in two wing-cracks about 25 μs after cutting seam cartridge blasting;and the largest width of wing-crack is 2.5 cm.While in closed joint experiment,a caustic appears 1 μs after cutting seam cartridge blasting,which is 24 μs ahead of open joint and the largest width of wing-crack is 5.6 cm.The dynamic stress intensity factor（SIF） of wing-crack changes from small to large firstly,and then falls from large to small.During the initial stage,dynamic stress intensity factor KⅡ^d is smaller than that of KI^d.The peak value of closed joint is larger than that of open joint;the former is 1.72 MN/m^3/2,and the latter is 1.28 MN/m^3/2.The research results can provide theoretical basis for directional fracture with controlled blasting of jointed rock mass.