饱和软土地层管幕暗挖法施工风险及对策研究

传统暗挖施工方法难以在含水量高、承载力低的饱和软土地层适用，管幕暗挖法可为软土地层暗挖施工提供新的途径。目前管幕暗挖法设计和施工经验不成熟，工程实施难度大，施工过程风险控制尤为重要。为此，结合上海市轨道交通14号线桂桥路站管幕段工程实例，从风险管控角度论述管幕暗挖法施工过程中管幕顶进精度、MJS加固地内压力控制、内衬墙倾覆、融沉注浆、开挖过程中坍塌和涌水等风险因素，并提出相应对策。研究结果表明： 1）在软土地层进行管幕暗挖法施工大断面地下空间是可行的，施工风险总体可控； 2）管幕顶管顶进工序是管幕暗挖法实施的基础，开挖支撑是该工法施工风险控制的关键工序，同时也是造成地面沉降的主要工序。

Research on Construction Risks and Countermeasures ofPipe roof Undercutting Method in Saturated Soft Soil

The traditional underground excavation method can hardly be applied to the saturated soft soil with high water content and low bearing capacity, while the pipe roof undercutting method provides a new way for soft soil excavation construction. At present, the design and construction experience of pipe roof undercutting method are not mature, which leads to great difficulty. The risk control is particularly important during construction. Hence, based on the engineering practice of the pipe roof section of Guiqiao Road Station on Shanghai Metro Line No. 14, some risk factors such as advancing precision of pipe roof, MJS reinforced underground pressure control, lining wall overturning, melting and grouting, collapse and water gushing during excavation are discussed from the perspective of risk control, and the corresponding countermeasures are put forward. The analytical results show that: (1) It is feasible to construct large cross section underground space by pipe roof undercutting method in soft soil, and the construction risk is generally controllable. (2) The jacking process is the basis for the implementation of pipe roof undercutting method, the process of excavation and support is the key process for the construction risk control and also the main factor causing ground subsidence.