潜盾隧道受邻近工区近接施工影响评估及分析-台北市政府捷运工程局.PDFVIP

捷運技術半年刊 第 期 213 48 潛盾隧道受鄰近工區近接施工影響評估及分析 1 2 摘要 擁擠的都市地下空間中，於軟弱土層進行潛盾隧道開挖及隧道近接施工之案例日益增 多，而潛盾隧道於掘進期間或完工後 ，受鄰近工區深開挖影響，可能造成環片側向解壓 ，進 而促使環片異向變形量增加而導致裂縫形成 ，嚴重者甚至影響結構穩定性。本文以捷運隧道 近接施工案例 ，檢討環片結構的安全性 ，考量環片除現有之受力情況外，應在已有變形條件 下 ，對後續施工 （含捷運主體及鄰近工區）可能產生之解壓 、地面加載、地面活載重及地下 水位等因素造成之土水壓力變化 ，再疊加地震力效應加以評估 ，並以土壤與結構互制之力學 數值分析模式，利用二維有限元素分析程式PLAXIS 進行重要性的結構強度及穩定性評估工作 。 關鍵字：潛盾隧道、近接施工、變形、垂直變位、土壤結構互制、有限元素模式、數值分析 Evaluations and Analyses of Impact on MRT Shield Tunnels by Adjacent Construction Bor-Shing Chen1Hsu-Chou Yu2 Abstract An increasingly common occurrence in confined urban underground spaces is shield tunnel excavation while other construction is conducted nearby on weak stratums. During excavation or after completion, deep excavation for adjacent construction could cause tunnel ring to decompress toward one side leading to an increase in anisotropic deformation of tunnel segments that result in cracks and even, in serious cases, structural instability. This paper aims to review the structural safety of tunnel rings by taking construction adjacent to MRT tunnels as an example. In addition to giving geotechnical considerations to the existing pressure on the ring, the authors also evaluate soil-water pressure variations for future construction including MRT main structure and adjacent construction sites that might be caused by the following factors: decompression, ground loading and surcharge, and underground water level, as well as seismic effect. Furthermore, based on a numerical approach of soil-structure interaction, the computer software PLAXIS of 2D finite element analysis has been used signif