上软下硬复合地层盾构隧道设计施工难点及对策研究

基于国内上软下硬地层盾构隧道典型工程案例，对上软下硬地层盾构工程案例区域分布特点及发展趋势、施工主要问题及其产生的原因进行分析。在此基础上，分别从隧道设计、盾构设计及工程实施的角度提出相应的对策措施，并结合相应的工程实例进行阐述。 研究得到上软下硬地层盾构实施主要问题，包括刀盘刀具磨损、刀盘结泥饼、刀盘卡死、排土器喷涌、盾构掘进姿态不良、衬砌损坏、地表沉降过大等方面。针对这些问题，采取如下措施： 1）隧道设计上可采取线型避让、特殊地层预处理、隧道结构特殊构造设计进行应对； 2）盾构制造上应充分考虑刀盘刀具、盾构机驱动、防冲刷及泡沫注入口的优化和超前地质探测装置的增设； 3）在施工上应优化施工参数，加强巡视和监测，做好应急预案。

Difficulties and Countermeasures in Design and Construction of  Shield Tunnels in Upper soft and Lower hard Stratum

Based on the typical engineering case of the shield tunnel in the upper soft and lower hard stratum in China, this paper analyzes the regional distribution characteristics, development trend, main construction problems and causes of the upper soft and lower hard stratum shield engineering cases. On this basis and combined with corresponding engineering examples, the corresponding countermeasures are proposed and expounded from the perspectives of tunnel design, shield design and engineering implementation. Main construction problems that obtained from the study include cutter head and cutter abrasion, mud cake formation on cutter head, cutter blocking, conveyer spewing, bad attitude of shield tunneling, lining damage, large surface subsidence and so on. In response to these problems, the following countermeasures are proposed: (1) Tunnel can be designed with line avoidance, special formation pretreatment, special formation design of tunnel structure. (2) Shield tunneling machine manufacture should take full consideration of optimizing cutter head and cutter tool, shield machine drive, anti scour and foam injection port, and addition of advanced geological detection devices. (3) Optimize construction parameters, strengthen inspection and monitoring, and make emergency plans.