盾构掘进破坏孤石诱发地层塌陷的灾变机制研究

Study of Mechanism of Ground Subsidence Induced by Boulder Breaking during Shield Tunneling

孤石地层因勘察、施工处理困难,使得隧道穿越该地层时面临风险。针对因盾构掘进破碎孤石后造成地层空洞,并最终引发地层塌陷的现象,利用研发的随机多边形生成方法,在离散元软件PFC2D中建立隧道孤石地层开挖模型,研究隧道掘进破碎孤石诱发地层塌陷的灾变机制及其影响范围。研究结果表明:根据孤石所在不同方位可以定性判断地表突然塌陷位置;当孤石粒径大于临界粒径或隧道埋深小于临界埋深后,孤石切削不当将引发地层塌穿型坍塌;在相同孤石粒径时,孤石形状的改变对地层位移影响甚微。

Tunneling in boulder strata may face great risks due to the difficulty in detection and treatment of boulders,i. e. ground hollow and ground subsidence. Therefore,it is worthwhile exploring ground subsidence pattern and associated mechanism when boulder encountering. By integrating the methodology for simulating irregularly shaped particles into PFC2 D,the discrete element model of tunneling in boulder strata is established; and then parametric analysis is performed. The analytical results show that：（ 1） The location of ground subsidence can be estimated according to the position of boulder.（ 2） Inappropriately tunneling would induce ground collapse,especially when boulder diameter or buried depth of tunnel is beyond critical value.（ 3） In case of same particle size,tunneling-induced ground displacement is hardly affected by shapes of boulders.