穿黄工程盾构始发井内衬混凝土逆作法施工技术

南水北调中线一期穿黄工程盾构始发竖井项目是国内迄今为止地连墙厚度最厚、成墙深度最深、开挖深度最大的工程案例。作为典型的超深基坑工程，该工程由于地质条件、荷载条件、施工条件的复杂性，施工难度和风险极大。根据实际情况，采用地下连续墙逆作法辅以监控量测和信息反馈等施工手段，解决了竖井开挖和支护施工带来的一系列结构稳定问题，避免了传统基坑支护方法带来的各种施工风险。结合工程施工情况，阐述了逆作法施工工艺和关键工序及控制要点，同时对施工中出现的问题进行分析并提出了相应的施工对策。

Technology of Top down Construction of Concrete Lining of Shield Launching Shaft of Yellow River Crossing Tunnel Project

The shield launching shaft of the Yellow River crossing tunnel on the central route of south to north water transfer project has the thickest and deepest diaphragm walls in China and is the deepest foundation pit in China. As a typical extra deep foundation pit works, the launching shaft, due to the complex geology conditions, complex loading conditions and complex construction conditions, has great construction difficulties and great risks. Construction technologies, including top down construction of diaphragm walls, monitoring and information feedback, are adopted on basis of the actual conditions, which successfully solves the structural stability problems caused by shaft sinking and supporting and successfully avoids all the construction risks caused by traditional foundation pit supporting technologies. Top down construction techniques, key construction processes and key control points are presented in the paper on basis of the construction practice. Furthermore, problems occurring during construction are analyzed and countermeasures are proposed.