雙圓型潛盾機開挖向前推進,引致土體內部狀況改變,造成地盤在垂直、橫向及縱向三個方向上之變位,實際上乃為一個三度空間問題。本文以桃園國際機場捷運線台北三重段CA450A標工程為案例,運用有限元素法Plaxis 3D Tunnel套裝軟體,以三向度分析模型來模擬實際之雙圓型潛盾隧道開挖情形。雙圓型潛盾隧道(Double-O-Tube Shield Tunnel) 案例以PLAXIS數值分析7處監測斷面之地表沉陷量,繪出地表沉陷之縱向變形量曲線及找出開挖面前方之先期變形曲線關係,並與現場監測沉陷觀測資料及經驗公式進行地表沉陷槽相互比較,由分析成果驗證Plaxis 3D Tunnel應用於雙圓型潛盾隧道施工引致地表沉陷分析之適用性,期能供後續雙圓型潛盾隧道工程應用參考及經驗傳承。
The internal conditions of a soil body are altered as the double-o-tube shield tunnel boring machine advances, leading to ground displacements in vertical, horizontal and longitudinal directions. In reality, it is a 3-dimentional issue. The Contract CA450A of Taipei-Sanchong Section, Taoyuan International MRT Line was selected for the study. The finite element analysis program, Plaxis 3D Tunnel, was introduced to generate a 3D analysis model for the simulation of excavation of double-o-tube (DOT) shield tunnel in reality. 7 monitoring cross sections were selected in the DOT shield tunnel for the analysis of ground settlement using PLAXIS. The longitudinal displacement of ground settlement vs. the initial displacement in front of the excavation surface was plotted, and compared with the ground settlement troughs developed using the in-situ monitoring data and empirical formulae. The analysis result demonstrated the feasibility of using Plaxis 3D Tunnel for ground settlement analysis in the construction of DOT shield tunnel. It is hoped that the result will serve as a reference for DOT shield tunnel construction and experience to pass down to future engineers and researchers.