浅埋软岩地下厂房开挖支护设计仿真计算

Simulation Calculation of Excavation and Support Design for Shallow Buried Soft Rock Underground Powerhouses

浅埋软岩地下厂房的开挖中,软岩抗压、抗拉强度较低,支护不当洞室变形过大会导致围岩失稳。依托于国外某水电站地下厂房,对于洞室开挖和支护进行有限元仿真计算。先对深埋巷道进行分析,使用Mohr-Coulomb屈服准则,标定不同黏聚力残余和摩擦角残余下的屈服区变化规律和计算结果准确性。在此基础上,模拟地下厂房的开挖,计算结果表明,塑性区集中于软弱围岩附近,沿倾角方向扩展。黏聚力和摩擦角的残余越低,围岩的屈服范围增大,锚杆屈服单元数增加。围岩摩擦角残余tanφ'=(0.7~0.9)tanφ,黏聚力残余c'不低于0.5c时,围岩变形最大值在18~31 cm。在原有设计上,使用管棚支护、板桩、置换岩体等措施对洞室关键部位的变形的进行控制,仿真计算结果表明围岩变形得到控制,达到稳定要求。

In the excavation of shallow-buried soft rock underground powerhouses,the low compressive and tensile strength of soft rock can lead to significant deformation and instability of the surrounding rock if not properly supported.This paper,based on an underground powerhouse of a hydropower station abroad,employs finite element simulation to analyze the excavation and support of the cavern.Initially,the analysis focuses on deep-buried tunnels using the Mohr-Coulomb yield criterion to calibrate the variation patterns and accuracy of yield zones under different residual cohesion and friction angles.Subsequently,the excavation of the underground powerhouse is simulated.The results indicate that the plastic zone is concentrated near the weak surrounding rock,expanding along the dip direction.Lower residual cohesion and friction angles will increase the yield range of the surrounding rock and the number of yielding units in rock bolts.When the residual friction angle of the surrounding rock is tanφ'=(0.7~0.9)tanφ,and the residual cohesion is not less than 0.5 times the original,the maximum deformation of the surrounding rock ranges from 18 to 31 cm.Based on the original design,measures such as pipe-shed support,sheet piles,and rock mass replacement are used to control deformation at key parts of the cavern.Simulation results show that the deformation of the surrounding rock is controlled,meeting stability requirements.