大断面公路板岩隧道开挖与支护数值模拟研究

Numerical simulation study on excavation and support of slab tunnel in large section highway

为了研究上下台阶法和CD法等不同施工工法及不同开挖步距下对大断面板岩隧道开挖围岩受力及变形的影响规律,基于有限元基本原理对各隧道的施工工况进行模拟分析,得到了隧道开挖过程中软弱围岩的应力场和位移场,并对隧道围岩稳定性进行了探讨.研究结果表明:采用两台阶法模拟隧道开挖过程中整个施工过程中应力最大值为3.550 MPa,洞室周边的应力影响范围为5~20 m,在隧洞跨径的1.5倍以内;采用CD法模拟隧道施工时洞周发生的位移较小,拱顶下沉和水平收敛的位移量与两台阶法施工的位移量相比分别减少了27.8%和34.0%;模拟不同开挖步距下隧道拱顶沉降和水平收敛的位移变形大致表现出二次多项式的函数关系,为隧道施工期的安全稳定及控制技术提供数据支撑及理论依据.

In order to study the influence of different construction methods such as full upper and lower step method and CD method on the stress and deformation of surrounding rock in large fault face rock tunnel excavation under different excavation steps,the construction of each tunnel is analyzed on the basic principle of finite element The simulation analysis shows the stress field and displacement field of the weak surrounding rock during the tunnel excavation process,and discusses the stability of the tunnel surrounding rock was discussed.Results show that the maximum stress during the tunnel excavation process is 3.550 MPa,and the stress around the cavern is 5-20 m,which is within 1.5 times of the span of the tunnel.The CD method is used for simulation,and the displacement of the tunnel is small when the tunnel is constructed.The displacement of the dome sinking and horizontal convergence is reduced by 27.8%and 34.0%,compared with the displacement of the two-step construction.The tunnel vault is simulated under different excavation steps.The displacement deformation of settlement and horizontal convergence generally shows the function relationship of quadratic polynomial,which provides data support and theoretical basis for the safety and stability and control technology of tunnel construction period.