软弱围岩隧洞位移和应力释放规律研究

软弱围岩强度低、自稳能力差,在隧洞施工中易引起不同程度的塌方,造成生命财产的损失。因此,研究及时支护情况下软岩隧洞围岩的位移和应力释放规律显得尤为重要。笔者采用三维数值方法系统研究了隧洞开挖过程中的位移变化规律,并结合二维数值分析方案研究了围岩应力释放系数随工作面推进的关系。研究表明:(1)埋深、洞径和洞型等对拱顶位移释放系数影响较小,而岩性对其影响显著;(2)拱顶位移释放随应力释放变化过程大致可分为3个阶段,且岩性越差达到相同位移释放率时所需的应力释放率也越大;(3)研究断面前后一倍洞径是围岩应力调整的主要阶段,且应力释放率随岩性的弱化而增强;(4)初期支护对岩性较差的隧洞效果更明显。

Release Law of the Displacement and Stress for the Soft-rock Tunnels

Because of the poor strength and lack of self-supporting ability of soft rock,it is easy to cause landslide in tunnel construction and create loss of life and property.Therefore,the study on the releasing rules of the displacement and stress of underground cavern is very important.The displacement variation of surrounding rock when the face is advancing and the stress release rule are studied by using two-dimensional numerical analysis scheme.This study shows that:(1 ） the release coefficient of displacement is less affected by the depth,diameter and shapes of the tunnel and is significantly impact by lithology;(2） the displacement release curve against the stress release ratio can be roughly divided into three phases and the stress release ratio increases with the weaken of lithology;(3 ） the main release stage of stress is in-1 D～ 1 D of the analytic section and the rate of stress relieving increases with the decrease of lithology;(4 ） the supporting effect is more significant for the tunnel in poor surrounding rock.