浅埋隧道大管幕施工台阶法几何参数优化

Geometric Parameters Optimization of Shallow Tunnel by Step Method for Large-Tube Curtain Construction

研究了浅埋隧道下穿高速公路大管幕施工的台阶法几何参数优化问题.以重庆新白杨湾隧道工程为依托,采用数值模拟方法分析不同台阶参数对初支受力、围岩变形、开挖面稳定性以及对现场施工的影响规律.研究结果表明:拱顶沉降和水平收敛随着台阶长度增大而增大,应适当减小台阶长度;拱顶沉降和水平收敛随着台阶高度增大而减小,但应控制在合理范围;开挖面纵向位移随着台阶高度增大而增大,开挖面主应力随着台阶高度增大而减小.结合对现场施工便利性和施工效率的影响,最终确定台阶高度和长度分别取值在5.9 m和20 m左右时为最优参数方案.

The optimization of step method geometry parameters for large-tube curtain construction in shallow tunnels was studied. Relying on the Xinbaiyangwan tunnel project of the Chongqing east ring line railway hub, the numerical simulation method was used to analyze the influence of different step parameters on the initial support bearing capacity, rock deformation around, excavation surface stability and on-site application, and analyze the theoretical and monitored values comparatively. The results show that the monitored value and the theoretical value are of the same order of magnitude, which verifies the rationality of the computational model and the reliability of the results. It can be used as a reference program for future projects. From the perspective of whether the initial support bearing capacity was safe to consider, the step height of 4.7 m or the step length of 24 m exceed the allowable the initial support bearing capacity value, so the step height should be controlled at 5.3~6.5 m, and the step length should be controlled at 18-22 m. The vault settlement value and horizontal convergence value increase with the increase of the step length, so the step length should be appropriately reduced during construction. As the height of the step increases, the settlement value and horizontal convergence value of the vault decrease, and then increase after a certain degree, so the step height should be controlled within a reasonable range. As the height of the step increases, the longitudinal displacement of the excavation face increases, and the principal stress of the excavation face decreases. Combining with the impact on site construction convenience and the construction efficiency, it is finally determined that the step height and the step length are respectively 5.9 m and 20 m,which is the optimum parameter scheme.