一次扣拱暗挖法隧道开挖步序优化与地表沉降预测

Excavation Sequence Optimization and Surface Settlement Prediction for Bored Tunnel with Cast in-situ Arch

一次扣拱暗挖逆作法作为一种新型的地铁车站施工方法已经应用于多处地铁车站建设,但该方法的理论研究滞后于工程实践。针对该方法施工过程中的施工步序优化与地表沉降预测等技术难题,以长春市轨道交通5号线人民广场站为工程依托,利用GTS NX软件进行一次扣拱暗挖逆作法隧道开挖全过程地表沉降数值模拟分析,基于地表沉降对导洞开挖步序进行优化,并借助高斯函数建立地表沉降预测模型。研究结果表明:(1)隧道开挖顺序的不同导致周围地表沉降总量不同,“先上后下、先边后中”的开挖顺序对地表沉降扰动最小;(2)多个导洞开挖会受到“群洞效应”的影响,开挖步距在9~15 m时对地表沉降的影响较小且可以根据工期进行适当调整;(3)高斯函数的预测与数值计算得到的地表沉降变化规律基本吻合,高斯函数可以有效预测由先导隧道引起的地表沉降。

As a new construction method of subway station,the top-down bored excavation method with cast in-situ arch has been widely applied in many subway stations,but the theoretical research of this method lags behind the engineering practice seriously.Based on the people’s square station project of Changchun rail transit line 5,and in view of the construction sequence optimization and the surface subsidence prediction,this paper uses the GTS NX to simulate and analyze the surface subsidence in the construction process of the top-down bored excavation with cast in-situ arch,optimize the pilot tunnel excavation sequence based on the surface subsidence,and establish the prediction model of surface subsidence by Gaussian function.The results show that:(1)different excavation sequences result in different total surface settlements,and the excavation sequence of“up-down and side-middle”has the least disturbance to the surface settlement.(2)The excavation of multiple pilot tunnels will be affected by“group cavern effect”,and the excavation step distance between 9~15 m has little influence on the surface settlement,and can be adjusted appropriately according to the construction period.(3)The prediction results of the Gaussian function are consistent with the change law of the numerical calculated surface settlement,and the Gaussian function can effectively predict the surface settlement caused by the first excavated pilot tunnel.