Abstract

The instability of weak surrounding rock around shallow buried tunnels induced by rainfall is a challenge for tunnel engineering and threatens construction safety. To reveal the influence of rainfall on the rock surrounding a tunnel, the results of experiments on the failure of surrounding rock under different rainfall intensities and durations using a self-developed test system are presented. First, the stress and seepage behaviors of the surrounding rock under rainfall were analysed, and the results showed that the stress increased while the pore water pressure decreased as the rainfall intensity decreased. It was more difficult to maintain vault collapse as rainfall intensity increased, and the particle erosion in the model intensified as the rainfall duration increased. The change in pore water pressure was greater than the change in stress, but the stress and pore water pressures influenced each other during rainfall. The influence of rainfall on the rock at the top of the tunnel was greater than that at the two sides of the tunnel because the seepage channels at the top of the tunnel were more developed and collapsed more easily due to smaller stresses. According to the phenomena of the surrounding rock observed during the test, the evolution of progressive failure under rainfall was roughly divided into eight stages: stability, water drop, continuous water flow, partial collapse, mud and water mixture, vault collapse, throughgoing collapse, and massive water and mud gushing. Furthermore, the final failure pattern of the surrounding rock consists of an excavation disturbance zone, vault damage zone and collapse failure zone. This research helps to reveal the progressive failure of surrounding rock around tunnels under rainfall conditions and can be used as a reference for designing disaster prevention strategies in practical engineering.

摘要

降雨引起的浅埋隧道周围较弱的围岩失稳是隧道工程面临的挑战，并威胁到施工安全。为了揭示降雨对隧道周围岩石的影响，利用自行开发的测试系统，给出了不同降雨强度和持续时间下围岩破坏的实验结果。首先，分析了降雨条件下围岩的应力和渗流行为，结果表明，随着降雨强度的降低，应力增加而孔隙水压力降低。随着降雨强度的增加，保管库倒塌更加困难，并且随着降雨持续时间的增加，模型中的颗粒侵蚀加剧。孔隙水压力的变化大于应力的变化，但是在降雨过程中，应力和孔隙水压力会相互影响。降雨对隧道顶部岩石的影响大于隧道两侧的岩石，因为隧道顶部的渗流通道由于应力较小而更发达且更容易塌陷。根据测试中观察到的围岩现象，降雨条件下渐进破坏的演化大致分为八个阶段：稳定性，水滴，连续水流，部分塌陷，泥水混合，拱顶塌陷，贯通塌陷，以及大量的水和泥浆涌出。此外，围岩的最终破坏模式包括开挖扰动区，拱顶破坏区和坍塌破坏区。