爆炸作用下隧道拱肩Ⅰ/Ⅱ复合型裂纹起裂及扩展规律研究

Study on initiation and propagation law of mixed mode Ⅰ/Ⅱ cracks in tunnel spandrel under explosion

为了分析隧道拱肩Ⅰ/Ⅱ复合型裂纹在爆炸荷载下的起裂及扩展规律,采用带有拱肩裂纹的岩石隧道模型(rock tunnel modelwith a spandrelcrack,RTMSC)进行了爆炸试验。试验中采用裂纹扩展计(crack propagation gauge,CPG)及应变片测试裂纹的起裂、扩展及止裂规律。数值模拟采用AUTODYN软件。裂纹尖端的动态应力强度因子k_(Ⅰ)^(d)(t)和k_(Ⅱ)^(d)(t)(SIFs)的计算采用ABAQUS软件。结果表明:(1)裂纹在扩展过程中,在扩展路径上出现了拐点,同时在拐点处存在较为明显的"止裂"现象。(2)炮孔位置显著影响裂纹的起裂、止裂和扩展。(3)裂纹扩展过程中,动态能量释放率不是一个常数。(4)随着裂纹扩展速度的增加,Ⅰ型和Ⅱ型临界SIFs逐渐减小。

In this paper,a rock tunnel model with a spandrel crack(RTMSC) was proposed,and the initiation and propagation rule of mixed mode Ⅰ/Ⅱ cracks under blast loading were studied. Crack propagation gauge and strain gauge were used in the experiment to monitor crack initiation,propagation and arrest. AUTODYN code was used for numerical simulation,and ABAQUS code was used to calculate the dynamic stress intensity factors k_(Ⅰ)^(d)(t) and k_(Ⅱ)^(d)(t)(SIFs). The results show that:(1) in the process of crack propagation,there are crack arrest points on the propagation paths in which crack propagation time is relatively long,(2) bore locations affect crack initiation,arrest and propagation significantly,(3) in the process of crack propagation,the dynamic energy release rate is not a constant,and(4) with increasing the crack propagation speed,critical SIFs of both mode Ⅰ and mode Ⅱ decrease gradually.