基于层次分析法的浅埋大跨城市隧道扁平率优化研究

Study on Flat Ratio Optimization of Large-span Shallow Buried City Tunnel Based on Analytic Hierarchy Process

对浅埋大跨城市隧道而言,合理的扁平率设计对于节约成本和提高结构安全性都有至关重要的作用。依托某典型工程,提出基于层次分析法原理的扁平率优化流程。首先对该工程的地质条件进行分层概化,确定地层及支护的物理力学参数和备选的扁平率,建立数值模型网格,利用有限差分软件模拟5种不同扁平率下隧道地层与支护的力学响应;再通过层次分析法对影响隧道经济性、稳定性与安全性的开挖面积、地表沉降、拱顶沉降、水平位移、支护受力特性及塑性区面积进行优化并计算其权值,最终选出最优的扁平率。

The design of reasonable flat ratio for large-span shallow buried city tunnel has very important effect on cost saving and structural safety improving. Based on some typical tunnel engineering, the method of evaluating stability of surrounding rock called failure degree index （FD]） and the fiat ratio optimization flow based on analytic hierarchy process （AHP） is proposed. Firstly, on the basis of the hierarchy of generalized geological conditions, the physical and mechanical parameters for stratum and support structure and the alternative flat ratio are determined. With the finite difference software FLAC3D, numerical model grids are built to simulate the mechanical response between stratums and support under 5 kinds of fiat ratios. Then, target values of excavation area, ground surface settlement, vault subsidence, horizontal convergence, support mechanical characteristic, plastic zone area, failure degree index, which affect the economy, stability and safety of the tunnels, are optimized using analytic hierarchy process （AHP） and determining their weight vectors. Finally, the optimal flat ratio is put forward.