隧道顶部岩溶对围岩稳定性影响的数值分析

以朝东岩隧道为背景，运用二维弹塑性分析研究了隧道顶部不同大小、不同距离的溶洞对隧道围岩稳定性的影响。研究结果表明：隧道顶部溶洞随距离的增大及围岩稳定性增强，距离与隧道开挖引起的释放位移之间存在明显的相关关系，影响的分界线大约为溶洞直径的2—3倍；在拱顶附近的周边释放位移与溶洞的大小成反比，而在隧道侧壁及底部的释放位移与溶洞的尺寸成正比；并详细地分析了应力场及塑性区的变化规律。

Numerical analysis of influence of karst caves in top of tunnel on stability of surrounding rock masses

Based on the excavation of Chaodongyan tunnel, a numerical analysis conceming the influence of karst caves in the top of tunnel on stability of the surrounding rock masses is carried out by using the ANSYS software system; the yield initiation is assumed to occur following Druck-Prager failure criterion. The results of numerical modeling show that the stability of the surrounding rockmass of the top of tunnel increases with increace of the distance between the karst cave and tunnel; and reduces with increace of the karst cave size. There is a good relationship between the deformation of the surrounding rockmass and the distance from the karst cave to tunnel. The limited distance between the karst cave and tunnel is about 2-3 times of the diameter of karst cave. The character of stress field and plastic district of the tunnel surrounding rock masses is discussed.