岩溶区隧道围岩--支护体系稳定性研究

岩溶是地下水地质作用的过程和结果，是隧道建设面临的不良地质现象之一。正在建设中的某高速公路隧道出口段岩溶地质作用强烈，溶隙、孔洞发育，且受构造变形及后期淋滤溶蚀作用强烈，力学强度低，岩性复杂。其角砾状粘土岩和水云母粘土岩多已泥化成粘土，遇水易膨胀。岩溶区隧道围岩——支护体系的稳定性是该隧道建设面临的主要问题。文章结合隧道施工过程中的围岩变形监控量测和三维弹塑性有限元数值仿真模拟对隧道围岩——支护体系的稳定性进行了研究。围岩水平收敛和拱顶下沉位移及速率变化特性表明，在监测时段内隧道围岩无趋于稳定的迹象。施工动态力学数值仿真模拟表明，在初期支护条件下，围岩出现了较大范围的塑性破坏区，两隧道之间(间距45．0m)围岩破坏接近度达到0．70，最大竖向位移达到3．0mm，表明隧道全断面施工时，两隧道相互作用影响程度较大。为确保隧道围岩——支护体系的稳定，选择合理的施工方法，制定切实可行的支护方案提供了信息。

Study on stability of tunnel surrounding rock-support system in karst region

Karst is a process and result of groundwater geologic function and it is one of bad geological phenomenon facing tunnel construction.At the exit section of a freeway tunnel in building,karst geological process is strong,solution crack and pore-hole are developed,tectonic deformation and later period eluviation-solution is also strong and rock mass mechanical strength and lithologic character are complicated.Brecciated clay rock and hydromica clay rock at tunnel exit section have been almost argillized clay and the clay is easy swelling when encountering water.The stability of surrounding rock-support system in karst region is an important problem in tunnel construction.Combining surrounding rock mass deformation monitoring and three-dimension elastic-plastic finite element numerical simulation,the stability of surrounding rock-support system was analysed in this paper.Characteristics variation of surrounding rock horizontal convergence displacement and deformation ratio,crown settlement displacement and deformation ratio shows that surrounding rock of tunnel mass did not exist any stable trend in the monitoring period.Numerical simulation and modeling of tunnel excavation dynamic mechanics show that surrounding rock of tunnel appeared large scope of plastic failure under the condition of initial support measures,and degree of surrounding rock mass approach failure attained to 0.70 and the maxim vertical displacement attained to 3.0mm between the two parallel tunnels (tunnel spacing equals to 45.0m).These characteristics made it clear that the two parallel tunnels interacted considerably at full-face excavation.This study has provided information for ensuring tunnel surrounding rock-support system stabiligy,selecting reasonable method of excavation,and drafting feasible and practicable support measures.