潛盾機到達井壁外棄殼施工控制案例及分析

捷運工程各區段標之工程介面通常在潛盾隧道與站體之聯繫段亦即潛盾到達井，目前捷運站體之設計大都是以站體兩側作為潛盾隧道之發進井或到達井使用，由於各區段標站體之施工時程與規模不盡相同，因此潛盾隧道基於工期因素及需重複使用潛盾機時，故常在兩區段標工程介面處考量以潛盾機棄殼方式進行施工，通常到達工作井於潛盾機到達前皆需完成底版，提供施作到達鏡面破除作業，使得潛盾機可進入工作井內做完整之拆解，或者將潛盾機嵌入擋土壁內做棄殼方式之拆解，以減少潛盾機與擋土壁鏡面間之縫隙進而降低後續作業的危險性。本研究擬以台北捷運蘆洲線施工潛盾機於到達井連續壁外棄殼案例探討其面臨之風險，包括停機拆解、超級點井工法輔助降水、棄殼期間地盤止水以及站體連續壁因開挖所引致側向變位使JSG地盤改良區產生縫隙水路，造成破鏡時滲水等項目進行探討與說明；再者，潛盾機到達棄殼之輔助作業包括在潛盾機到達處先行JSG地改，再以試水檢驗地盤止水性及潛盾機到達後即進行機殼背填灌漿、土艙分階排土、漏水確認及機內補償灌漿，同時以超級點井工法嘗試降低松三層水壓，並於松三層和松五層埋設豎管式水壓計了解降水期間孔隙水壓變化之互動關係，同時監測鄰近建物之沉陷，並且依據工址豎管式水壓計、水位觀測井、地表淺式沉陷點與建物沉陷點之監測歷時，研判抽降水引致地表沉陷影響範圍，然後潛盾機歷經兩次拆解完成到達棄殼作業，最後進行鏡面破除，順利貫通隧道。

關鍵字

工程介面；潛盾機棄殼；鏡面破除；超級點井

並列摘要

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.

並列關鍵字

Engineering design ； Shield disassembly of TBM ； Mirror face excavation ； Super well-point

參考文獻

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潛盾機到達井壁外棄殼施工控制案例及分析

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