埋深对软弱隧道围岩破坏影响机制试验研究

通过室内模型试验,研究公路隧道IV,V级围岩在不同埋深条件下全断面开挖时的围岩破坏情况,实现自重应力场作用下毛洞状态时隧道围岩破坏过程的试验模拟,得到拱形塌方和塌穿型塌方2种围岩破坏模式。试验结果表明:隧道围岩的破坏从拱顶开始,并逐渐向上发展;埋深越小,隧道越易发生塌穿型塌方,而当埋深小于某一值时,因隧道开挖后围岩应力未超过围岩强度,隧道反而能保持稳定状态;对塌穿型塌方,隧道埋深越大,开挖后围岩维持稳定时间越短,塌方程度越严重,塌方向地表发展得越快;对同一类型的塌方,隧道埋深越大,塌方后隧道周边应力变化幅度越大。

EXPERIMENTAL STUDY OF INFLUENCE MECHANISM OF BURIED DEPTH ON SURROUNDING ROCK FAILURE OF TUNNEL CONSTRUCTED IN SOFT ROCK

The failure conditions of grades IV and V surrounding rocks in highway tunnel under different buried depths are studied through a number of model tests. The test simulation of failure process of non-supported tunnel under gravitational stress is carried out successfully；and two failure modes of arch collapse and caving collapse are obtained. The test results show that the failure of surrounding rock initiates from arch crown of tunnel and develops upward progressively. The smaller the buried depth is，the more likely the caving collapse occurs. When the buried depth is less than a certain value，the tunnel can maintain stability because the stress of surrounding rock induced by excavation does not exceed the strength of surrounding rock. For the caving collapse，the larger the buried depth is，the shorter the time of surrounding rock¢s stability is，the more serious the collapse degree is，and also the faster the collapse developing to ground surface is. For the same collapse type，the larger the buried depth is，the larger the changing amplitude of the stress of surrounding rock is.