倾斜岩层大断面隧道塌方机制的数值模拟

Numerical simulation of collapse mechanism of large-section tunnel in inclined layered rocks

塌方是隧道施工中出现的主要安全事故,研究隧道塌方产生的机制对于保证隧道施工安全具有重要意义。以穿越倾斜岩层段某隧道塌方事故为工程背景,基于围岩的工程力学特性,采用数值分析和现场监测方法研究隧道塌方的力学机制。结果表明:在开挖爆破振动荷载作用下,隧道断面拱部左侧节理岩层极易出现超挖,隧道左侧拱腰处的塑性区显著大于右侧,使左侧拱腰处内侧出现拉应力;左侧拱腰处围岩压力显著大于右侧,造成支护结构的受力不均,初支喷层极易开裂,随着松动区范围逐渐增大,围岩压力逐渐增大,隧道变形迅速增大,极易造成围岩失稳而导致隧道坍塌。

Collapse is the main safety accident during the course of tunnel construction.It is very meaningful for ensuring the construction safety to study the collapse mechanism of tunnel.Taking the collapse of a tunnel crossing inclined rock layers as the engineering background,the methods of numerical simulation and field monitoring were used to investigate the collapse mechanism of tunnel on the basis of the engineering mechanical properties of surrounding rock.The research results show that under the action of excavation blasting vibrating load,over break is very easy to be seen at the left side of tunnel crown,and the plastic zone at the left arch waist is much bigger than the right side,which leads to the tensile stress in the left arch waist.And surrounding rock pressure is much bigger than the right side,which leads to asymmetric loads of supporting structure and the fractures at the inner side of shotcrete layer.With the enlargement of disturbed zone of tunnel,the surrounding rock pressure increases gradually,and the tunnel deformation icreases quickly,and the loss of stableness of surrounding rock eventually leads to the tunnel collapse.