富水圆砾地层盾构下穿火车站股道沉降控制技术研究

Settlement control study of shield tunnelling crossing railway station in round gravel strata

盾构下穿运营中的铁路股道对沉降控制有着更高的要求,南宁地铁1号线盾构下穿南宁火车站股道面临富水强渗透圆砾地层的挑战。首先介绍穿越火车站股道的沉降控制措施;接下来利用三维有限元分析软件MIDAS/GTS建立盾构穿越施工分步开挖的数值模型,讨论富水圆砾地层中等代层参数的取值,研究穿越过程中股道沉降变化规律,并对后续2号线穿越施工进行预测,在此基础上确定沉降控制指标;布设基于静力水准系统的沉降自动化监测系统,实现对盾构开挖引起的股道沉降的实时监控,并借助即时通讯工具实现穿越施工中信息的实时交互,通过调整工作仓泥水压力以减小沉降来说明基于自动化监测的微扰动施工控制机制。数值模拟和现场实测结果表明:盾构穿越火车站股道采用预加固措施是十分必要的,富水圆砾地层中采用桩筏基础加固能够满足沉降控制要求;在盾构穿越前利用三维数值仿真,能够模拟盾构穿越股道的沉降变化规律,有利于确定沉降监测范围和控制指标;利用远程自动化监控结合即时通讯平台,可以实现监测信息的实施自动化发布,将平台纳入到施工管理体系中,能够实现盾构穿越重要建构筑物的微扰动施工控制。

There is a higher demand on settlement control for shield tunnelling crossing railway station. The Nanning metro line one crossing Nanning railway station is confronted with the challengeable soil of round gravel with high permeability. The piled raft foundation beneath the railway tracks as well as some other control measures to reduce settlement is first introduced. Then the FEM-based shield tunnelling deformation prediction are used to study the change rule of the settlement induced by shield tunnelling. In addition,a real-time remote automatic monitoring system is proposed. By the means of instant messaging（IM） platform,all the participants concerned the project can know the settlement as well as the tunneling situation timely. According to the variation of the settlement data,the engineers gave orders to the operators in the tunnel to adjust the key tunneling parameters. The numerical simulation results and filed monitoring data indicate that its essential to reinforce ground before shield TBM crossing the railway track. The piled raft foundation is suitable for round gravel with high permeability. The FEM is helpful to determine the monitoring ranges and settlement control standards. With the feed-back control mechanism,the Nanning metro line one crossing Nanning railway station realized the micro-disturbed construction and the maximum settlement was only-4 mm.