既有溶洞对隧道围岩位移特征影响的数值试验

Numerical Experimentation of Influence of Karst Cave on Displacement Characteristics of Rock Mass

隧道穿越既有溶洞岩体施工时,隧道围岩位移变化特性不同于一般隧道。结合山岭隧道新奥法施工现状,首次提出了隧道位移空间效应的"先期位移"、"开挖瞬时释放位移"、"前期位移"和"后期位移"的新概念。基于对位移空间效应特征的新认识,通过数值试验系统研究了既有水平溶洞对隧道位移空间效应的影响,研究表明:①水平溶洞的存在将导致隧道围岩径向位移在开挖前和开挖瞬间明显增大,位移释放率增加;②水平溶洞的存在使得溶洞附近围岩的整体性减弱,围岩先期变形主要集中在掌子面前2.0倍洞径以内,其后期变形在掌子面推进到1.5倍洞径后就基本完成。

When a tunnel construction passes through the surrounding rock with karst caverns, the displacement change characteristic of rock mass is different with the common tunnel. On the basis of the present construction situation of Sinitic mountain tunnel method, the new concepts of ahead displacement, releasing displacement in excavating, early displacement and the later displacement, which are the new division from the tunnel excavation displacement three-dimensional effect, have been proposed. With the new understanding of the displacement three-dimensional effect characteristics, the influence of horizontal karst caves on displacement characteristics of surrounding rock has been analyzed with the numerical experimentation. The research results indicate： （ 1 ） the horizontal karst caverns will cause the earlier period and radial displacement in excavation to increase obviously, and the displacement release rate also increases; （2） the horizontal karst caverns will cause the surrounding rock integrity to be weakened, and the early period displacement will mainly concentrates inside the 2.0 times of hole diameter, its later displacement will basically complete after the tunnels is excavated to the distance of 1.5 times of tunnel＇s diameter.