雙圓型潛盾隧道案例研究-以機場捷運台北三重段為例

Abstract

本論文依據桃園國際機場捷運台北三重段CA450A 標DOT 潛盾隧道施工案例，探討DOT 潛盾機施工遭遇之問題及解決方法。本研究探討主題包含滾轉問題與控制方法、DOT 潛盾施工造成之地表沉陷槽、及DOT 與單圓雙孔潛盾施工工期與成本比較，並獲得以下各項結論與建議。 1. 施工之實測數據顯示，DOT 潛盾機盾身最大滾轉角度為0.38 度，小於滾轉量的設計極限值0.6 度。CA450A 標使用之滾轉修正方法包含：切刃盤反向旋轉、環片灌漿、及超挖刀修正，其中又以切刃盤反向旋轉最常被使用於修正微小角度滾轉之修正。 2. 本研究建議以疊加法及等面積法兩種經驗方法，預估DOT 潛盾施工造成之沉陷槽。結果顯示，疊加法及等面積法求出之沉陷槽非常相近，預估沉陷槽與實測沉陷槽之趨勢大致吻合。 3. 國內外沉陷實測數據顯示，沉陷槽之最大沉陷量皆偏離DOT 隧道中間點，6個監測斷面測得最大沉陷量介於12 mm~34 mm 之間，DOT 施工引致之地盤漏失率範圍為0.23 %~1.19 %之間，平均值為0.76 %。 4. 於出發段DOT 潛盾隧道之預估施工速率，為2.0 m/day，而實測結果為2.5m/day，較預估施工速率快25%。於正式掘進段預估施工速率為4.3m/day，實際施工速率為3.9 m/day。 5. 依設計單位評估，DOT 潛盾隧道進尺費為84.93 萬元/公尺，單圓雙孔潛盾隧道進尺費為58.56 萬元/公尺，昂貴的DOT 潛盾機造價與複雜雙圓環片製造及組裝費用，為DOT 潛盾隧道進尺費昂貴之主要原因。 6. 雖然DOT 隧道段施工費用比單圓雙孔隧道者高出4.5 億元，但是DOT 潛盾隧道可免除在淡水河床下方設置三處聯絡通道之費用3.3 億元。考量總工程費，DOT 潛盾隧道總工程費為19.6 億元，單圓雙孔潛盾隧道總工程費19.1億元，兩種工法總工程費僅差大約2.5%。

Based on the construction of Taoyuan International Airport access MRT with the Double-O-Tube (DOT) shield tunneling method, this thesis studies the difficulties encountered during construction. Major difficulties discussed included: rolling of the shield machine, ground settlement due to tunneling, and speed and cost of DOT shield tunneling. Based on this study, the following conclusions are made. 1. Field data indicated that the maximum rolling angle was 0.38o, which was less than the limiting design rolling angle of 0.6o. The measures adopted by the contractor to correct the rolling angle included: reverse rotation of the cutter disc,grouting through holes on lining segments, and overcut of ground with the copy cutter. The reverse rotation of the cutter disc was use most often to correct the rolling angle. 2. The superposition method and the equal-area method were proposed to estimate the ground settlement due to DOT shield tunneling. It was found that the settlement troughs determined with the two methods were similar. The estimated settlement trough was in fairly good agreement with the measured settlement data. 3. The maximum ground settlements measured at six different sections varied from 12 to 34 mm. The ground loss due to DOT shield tunneling varied form 0.23 to 1.19%. The average ground loss was 0.76%. 4. In the departure section, the estimated speed of DOT excavation was 2.0 m/day.The measured speed of excavation was 2.5 m/day, which was 25% faster than the estimated speed. In the normal excavation section, the estimated speed of excavation was 4.3 m/day, and the measured speed was 3.9 m/day. 5. Based on the calculation of the Detail Design Consultant, the construction cost for the DOT tunnel is NTD 849,300 dollar/m. The construction cost for the traditional circular-section twin-tube shield tunnels is NTD 585,600 dollar/m. The DOT shield tunnel was more expensive to build mainly because the expensive DOT shield machine, and the complex DOT ring manufacture and assembly. 6. Although the total cost for the DOT shield tunnel was NTD 450,000,000 higher than that for the circular-section twin-tube shieldtunnels. However, with the DOT shield tunnel, the cost NTD 330,000,000 dollars to construct three cross-passages under the Danshuei River could be avoided. Consider the total cost of lot CA450A,the total cost with a DOT shield tunnel is NTD 1,960,000,000 dollars, and the total cost with traditional shield tunnels is NTD 1,910,000,000 dollars. With the two tunneling methods, the difference in total cost is only 2.5%.