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Shield tunnel survey is a crucial part of underground tunneling operation. Many problems may arise when the heading alignment is incorrect. In particular, the shield tunnel heading in Metro system requires higher survey accuracy than typical sewerage or power mains pipeline. However, human factor sometimes creates a large error that leads to inaccuracy of tunnel. Alignment correction requires more manpower and resources to perform, and the following stage of construction is likely to be delayed. The study investigate techniques in performing the alignment management well in shield tunneling in Metro system. The center of lining sections set after heading is controlled within a tolerance of 10cm. However, it is very difficult to do so given that the outer diameter of a standard Metro tunnel is 6.1m and that of a tunnel boring machine is 6.24m. That is why it is specified in the Metro construction contracts that a tunnel boring equipment requires automatic tunneling management system. The automatic tunneling management system consists of a gyroscope and automatic survey systems, both of which may be slightly different in their functions but totally different in the way they are used. The study investigate how to use both of the above systems correctly and calibrate them with manual measuring, the repetitive calculations in manual survey, and how to introduce computer programs and complete tunneling instructions quickly. At present, most of Metro shield tunnels in Taiwan are done by joint venture with Japanese companies, which means that the technology for alignment control is kept in their hands, while Taiwanese engineers are only in charge of surveying. The Japanese companies are reluctant to provide details on lining installation and the development of tunneling instructions. Hopefully, this study will provide certain improvement for the shield tunnel construction technology in Taiwan.
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