超大断面隧道临近溶洞围岩突水失稳破坏特征分析

Analysis on the Failure Characteristics of Water Inrush and Instability of Surrounding Rock near Karst Cavern in Super-large Section Tunnel

为了研究超大断面隧道临近溶洞掌子面开挖的围岩突水失稳破坏特征,本文以武深高速李洞隧道为背景,利用FLAC 3D数值模拟软件建立了数值计算模型,分别分析了围岩应力、位移、塑性区和涌水量等关键因素随隧道开挖的变化规律,研究了溶洞水压对隧道围岩稳定性的影响规律。研究结果表明:(1)当掌子面距离前方岩溶隧道小于6 m时,掌子面与溶洞之间的围岩应力最大值达到6.32 MPa,掌子面最大位移迅速增大至约200 mm;(2)当掌子面距离溶洞-18 m~-8 m时,隧道掌子面涌水量处于200 m^(3)/h以下,当掌子面距离溶洞-8 m~-2 m时,涌水量迅速增大至7371 m^(3)/h,势必发生突水事故;(3)隧道掌子面最大位移和涌水量均与溶洞水压呈指数式增长关系,掌子面开挖遇前方有溶洞应采取疏水降压以及补强掌子面岩体的措施。

In order to study the large cross section tunnel near the cave of the water inrush of the surrounding rock excavation instability destruction features,Lidong tunnel of Wushen highway was taken as the background in this paper.Numerical model is established by numerical simulation software FLAC 3D,and the key factors the stress,the plastic zone,displacement and water inflow change rule of the surrounding rock with tunnel excavation was analyzed.The influence of water pressure on the stability of tunnel surrounding rock is studied.The results show that:(1)When the distance between face and karst tunnel is less than 6 m,the maximum stress of surrounding rock between face and karst tunnel reaches 6.32 MPa,and the maximum displacement of face increases rapidly to about 200 mm.(2)When the distance between the face of the tunnel and the cave is-18 m~-8 m,the water inflow of the tunnel face is less than 200 m^(3)/h.When the distance between the face of the tunnel and the cave is-8 m~-2 m,the water inflow rapidly increases to 7371 m^(3)/h,which is bound to cause water inrush accident.(3)Both the maximum displacement and water inflow of the tunnel face increase exponentially with the water pressure of the cave.When there is a cave in front of the tunnel face during excavation,measures should be taken to drain water and depressurize the rock mass of the tunnel face.