| Summary: | 碩士 === 國立臺北科技大學 === 土木與防災研究所 === 97 === It is very difficult to deal with the tunnel-shaft interface problem between different construction lots especially for metro system, which involves several factors such as differences in construction schedule and its scale. Besides, for shield tunnelling, contructors usually needed to reuse the shield machine in order to save cost , consequently, the disassembly outside the diaphragm wall of arrival shaft discussed herein was employed instead of conventional break of mirror-face. The particular disassembly engineering practice of Taipei metro system was adopted and further analyzing the risks while disassembly, including lateral displacement of diaphragm wall induced seepage failure.
The disassembly job outside the diaphragm wall consists of vacuum dewatering, ground improvement around arrival shaft, compensation grouting, leakage test and break of mirror-face, furthermore, the monitoring system was installed in field to investigate the pore pressure interaction between different sandy soil deposits in the Sungshan Formation during vacuum dewatering and monitored ground subsidence as well. The study conducts quasi three-dimensional numerical simulation, considering tidal effect and geotectonic faults, to predict the extent of drawdown and ground subsidence as well as further comparing with field measurement. As a result, the numerical results have good agreement with field measurement through calibrated quasi three-dimensional numerical model.
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