隨著城市的快速發展，地下空間的使用率逐漸增加。而淺層的地下隧道多使用明挖覆蓋法 (cut-and-cover) 並以矩形隧道形式建造，其優點在於方便施工且相關設施可最大化利用開挖空間，不同的土層會對隧道產生不同的影響，在高地下水位設置明挖覆蓋隧道時，應考慮上浮的影響。本研究以離心模型探討地下水位高程對矩形隧道動態反應的影響，並比較不同地下水位面時其加速度反應、孔隙水壓反應、地表沉陷量、隧道位移及旋轉角之變化。 本研究在80 g進行四組動態離心模型試驗，透過改變地下水位面高程，探討相對於隧道具有不同高度地下水位時，土壤液化程度與隧道動態反應的互制行為。試驗結果表示 (1) 隧道周圍受震激發的超額孔隙水壓會較自由場的超額孔隙水壓小；(2) 地下水位面高於隧道底部時，基盤震動造成隧道周圍土壤液化程度不同，引致隧道受震時的擺動(rocking)及旋轉(rotation) ；(3) 當地下水位高於隧道頂部時，地震會使隧道上浮且正上方地表隆起，然而越遠離隧道則地表高程變化則相對為向下沉陷。未來可以更進一步討論，當地下水位高於隧道時，在隧道旁的支撐開挖與隧道間的相互影響行為。 ;The shallow underground tunnels mostly use cut-and-cover and are constructed in the form of rectangular (box-shaped) tunnels, which have the advantage of being convenient for construction and related facilities can maximize the use of excavation space. Different soil layers will have different effects on the tunnel. When setting cut-and-cover tunnels with high groundwater levels, the effect of floating should be considered. This study investigates the impact of earthquakes on existing tunnels at different groundwater levels, and compares the changes in acceleration response, water pressure response, surface subsidence, tunnel displacement and rotation angle at different groundwater levels.
In this study, four sets of dynamic centrifugal model tests were conducted to explore the relationship between the earthquake and the tunnel by changing the depth of the groundwater table. The test results show (1) The soil pore water pressure around the tunnel is smaller than that of the free field (2) When the water level is higher than the tunnel , earthquakes can cause the tunnel to rocking and rotate (3) When the groundwater level is higher than the tunnel, the earthquake will cause the tunnel to uplift and the surface above it to heaving, but the further away from the tunnel, the greater the surface subsidence . Further discussions can be made in the future as to what the impact of supporting excavation next to the tunnel will be when the water level is higher than the tunnel.
