The engineering technology used in shield methods has made significant progress. The introduction of a multi-circle shield machine is being positively promoted for use as a means to enable rational construction of station sections of subway tunnels. In general, multi-circle shield sections are mostly short, so that advantages of this method are lost in terms of economical feasibility. In order to utilize one shield machine with maximum effectiveness, the removable three-centered slurry shield method has been developed. In this method, a removable type side shield machine is installed on both sides of a shield machine for excavation of a double-track cross section, to excavate multi-circle cross sections comprising double-track cross sections and station sections. This paper describes how this method was effectively employed for Subway No. 7 under construction in Tokyo. It will also discuss results of experimental research.
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