致密砂岩巷道模型试件动态起裂及止裂全过程分析

为了开展在不同冲击载荷作用下巷道围岩内裂纹的起裂、扩展及止裂等问题，以可调速冲击试验机进行动态加载试验，采用致密青砂岩制作裂纹巷道模型试件，并利用裂纹扩展计分别记录了动态起裂、扩展、止裂等时刻，对裂纹扩展速度的变化规律进行分析；随后采用AUTODYN有限差分法软件进行相应的数值模拟，数值模拟得到的裂纹扩展路径与试验结果基本一致。经过两者对比分析可知:随着冲击载荷作用的增加，裂纹平均扩展速度逐渐增大，随后趋于稳定值；预制裂纹的起裂时间随着冲击速度载荷的增加而逐渐降低，并在稳定值上下波动；随着冲击速度载荷的增加，裂纹扩展路径过程中的止裂时段逐渐变短。

Analysis on whole dynamical fracture process of tight sandstone tunnel model under impact loading

In order to investigate the properties of crack fracture time, propagation speed and arrest period in the surrounding rock of tunnel under different impact loading speed, the dynamic tests were performed by self-developed adjustable speed drop weight impact test system, and the tight green sandstone was selected to make the cracked tunnel specimens. A crack propagation gauge (CPG) was applied to measure dynamic initiation time, propagation speeds and arrest time, respectively. The properties of crack propagation velocity, crack fracture time and crack arrest period were discussed and analyzed. The corresponding numerical simulation was carried out by AUTODYN code, and the simulation results showed that the crack propagation speeds and crack fracture time generally agree with the experimental results, and crack arrest period also was calculated. The results show that crack propagation speeds increase with impact loading speed, but as the impact loading speed is larger than a certain value, the crack speeds tend toward a stable value; Crack fracture time decreases with the increase of impact loading speed, and as the loading rate is larger than a certain value, it tends toward a stable value; With the increase of the impact loading speed, the crack arrest period in the crack propagation path gradually decreases.