考虑初始损伤与填充荷载影响的岩溶隧道围岩稳定性分析

Stability analysis of karst tunnel surrounding rock considering initial damage and filling load

岩溶的存在不仅使地下工程围岩完整性下降,其内部填充物还会长期侵蚀周围岩体,使周围岩体带有不同程度的初始损伤。以重庆市陶家隧道为工程依托,分析了造成涌砂涌泥事故的主要原因,并借助有限差分软件FLAC3D 6.0开展了考虑初始损伤与填充荷载影响的岩溶隧道围岩稳定性分析。结果表明:隧道开挖导致的岩体卸荷与溶洞内部填充物的重力作用是导致涌砂涌泥事故的主要原因,岩体初始损伤对隧道拱顶围岩竖向位移及稳定性的影响不容忽视,建议初始损伤系数取值为0.4~0.5;填充荷载对下方隧道围岩稳定性的影响较大,当荷载取值大于75 t/m^(2)时拱顶围岩竖向位移明显增加,且稳定性急剧下降;溶洞截面面积越大时拱顶围岩竖向位移越大,溶洞与隧道拱顶之间岩层越薄时拱顶围岩竖向位移越大;填充荷载取值越大、初始损伤系数取值越大时,中间主应力(σ^(2))对隧道围岩稳定性的影响越大。

The presence of karst will not only reduces the integrity of the surrounding rock of underground engineering,but also erode the surrounding rock mass for a long time due to its internal filler,leading to initial damage on different degrees of the surrounding rock.Taking the Taojia Tunnel in Chongqing as the research object,the main causes of the sand surge accident were analyzed and the stability analysis of the surrounding rock of the karst tunnel under the influence of initial damage and filling load was carried out with the help of the limited difference software FLAC3D 6.0.The main conclusions are as follow.The unloading of rock mass caused by tunnel excavation and the gravity action of the filling material inside the karst cave are the main causes of sand and mud flooding accidents.The influence of initial damage of rock mass on the vertical displacement and stability of the surrounding rock of the tunnel arch roof cannot be ignored.It is suggested that the initial damage coefficient should be 0.4-0.5.The filling load has a great influence on the stability of surrounding rock.When the load value is greater than 75 t/m^(2),the vertical displacement of surrounding rock increases obviously,and the stability decreases sharply The greater the filling load and initial damage coefficient are,the greater the influence of intermediate principal stress(σ^(2))on the stability of tunnel surrounding rock is.