雙圓型潛盾隧道開挖造成之地盤沉陷

Abstract

本論文依據桃園國際機場捷運台北三重段，CA450A標雙圓型(Double-O-Tube, DOT)潛盾隧道施工案例，探討DOT潛盾工法之施工、監測、工期與施工造成之沉陷。本研究依據現地監測資料探討以雙曲線模式(hyperbolic model)模擬地表沉陷歷時曲線之適用性。根據國內外11筆DOT潛盾隧道施工之地表沉陷資料，本研究探討DOT潛盾機施工引致之地表沉陷槽寬度i值，及最大地表沉陷量Smax，並獲得以下各項結論。 1. 施工之實測數據顯示，CA450A標DOT潛盾機施工造成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。只要盾身滾轉量大於行動值0.2度，施工單位即視實際狀況以切刃盤反向旋轉、背填灌漿、及以超挖刀擴挖來修正潛盾機滾轉角度。 2. 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2.5 m/day，較預估施工速率快25 %。於正式掘進段預估施工速率為4.3 m/day，實際施工速率為4.55 m/day，較預估速率快5.8 %。於到達段預估施工速率為2.0 m/day，實際施工速率為4.3 m/day，較預估施工速率快115 %。 3. DOT潛盾隧道總工期預估400天，實際掘進總工期為360天，較預估工期減少10 %。 4. 國內外11筆DOT潛盾隧道施工造成地表沉陷槽監測數據顯示， DOT施工引致之地盤漏失率範圍為0.21 % ~ 1.34 %之間，平均值為0.85 %。 5. 以土壓平衡式DOT潛盾機施工，引致隧道中心線上方之地表沉陷歷時曲線，可以使用雙曲線關係加以模擬。 6. 本研究建議以Peck(1969)提出之常態分佈曲線，預估DOT潛盾施工造成之地表沉陷槽。現地監測沉陷資料顯示，以常態分佈曲線預估之沉陷槽與實測沉陷槽之分佈大致吻合。

Based on the construction of Taoyuan International Airport Access MRT with the Double-O-Tube (DOT) shield tunneling method, this thesis studies ground settlement due to tunneling. Based on the field data, the hyperbolic model is proposed to simulate the settlement-time relationship due to DOT shield tunneling. Peck(1969) suggested that the surface settlement due to shield tunneling can be decribed with a normal distribution curve. Based on the field data, measured at 11 different cases in 3 different countries, this study analyzes the settlement trough width parameter i and maximum surface settlement Smax due to DOT shield tunneling. Based on this study, the following conclusions are made. 1. Field data indicated that the maximum rolling angle was 0.38∘, which was less than the limiting design rolling angle of 0.6∘. As the rolling angle became greater than the management value of 0.2∘, action would be taken. The measures adopted by the contractor to correct the rolling angle included: reverse rotation of the cutter disc, backfill grouting, and overcut of ground with the copy cutter. 2. 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 4.55 m/day, which was 5.8 % faster than the estimated speed. In the arrival section, the estimated speed of excavation was 2.0 m/day, and the measured speed was 4.3 m/day, which was 115 % faster than the estimated speed. 3. The estimated total duration for DOT shield tunneling was 400 days. The actual excavation duration was 360 days, which was 10 % shorter than the estimated duration. 4. The ground loss due to DOT shield tunneling varied form 0.21 to 1.34 %, and the average ground loss was 0.85 %. 5. Field monitored data indicated that the settlement-time relationship induced by DOT shield tunneling can be properly described by the hyperbolic model. 6. Field monitored settlement data indicated that the settlement trough monitored in the field was in fairly good agreement with the normal distribution estimation proposed by peck.