Abstract:

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.

Key words: uppersoft and lowerhard stratum, shield method, tunnel, design, construction