隧洞岩爆应变能释放机理研究

Numerical Study on Strain Energy Release of Rockburst in Tunnel

为进一步认识隧洞岩爆应变能释放机理,获得岩爆过程完整演化图像,定义弹脆性细观损伤模型和刚度退化迭代算法,并将其嵌入有限元程序模拟一个深埋隧洞岩爆发生过程。结果表明:岩爆发生过程为首先在洞壁母岩中形成"V"形剪切滑移带,并从中分划出楔形岩爆体;随后岩爆孕育进入临界状态;最终楔形体挤压破坏,导致卸荷释放应变能。岩爆孕育、演化发生包含丰富细观力学机制:岩爆区的分划机制——剪切滑移;滑移带中的细观力学机制——张拉破坏;岩爆的临界状态——楔形体的极限平衡;岩爆能量释放——楔形体裂隙带卸荷。楔形体位移监测表明:岩爆发生时,楔形体经历弹性外鼓、卸荷回弹及片状抛出3个阶段,片状爆裂发生在卸荷回弹阶段。

In order to understand the mechanism of strain energy release and get a set of clear pictures of rock burst gestation, in the paper, we define the elasto-brittle damage model for meso cracks and the iterative algorithm for rigidness degeneration along with crack propagation and implant them into the program of FEM. As an example, we simulate rock bursts in a deeply buried tunnel. The results show as follows： Rock burst gestation can be divided into two stages, namely the wedge shaped mass（being called WSM for short） is partitioned from its mother rock and is crushed ＆ fractured by surrounding compression; in the first stage, the V-shaped shearing bands nucleate, extend and intersect, resulting in the WSM partition from its mother rock; in the second stage, the freedom of the WSM increases, thus generating a trend of WSM moving off from the mother rock and leading to WSM crushing-fracturing under surrounding compression and strain energy release. The meso mechanism of rock burst gestation is complicated, which includes： （I）shearing slipping—the partition mechanism of WSM from its mother rock; （II） tension induced cracks—the meso mechanism in the V-shaped shearing bands; （III）limit equilibrium—the mechanism of rock burst in critical state; （IV）crack bands induced unloading—the mechanism of strain energy release. The WSM displacement monitoring shows that during the process of rock burst, the WSM undergoes three stages： bulging outward by loading, springing back by unloading, and being thrown out as flakes one by one. Exfoliation occurs in the stage of springing back. The results conform to spot surveying.