| 摘要: | 活動斷層錯動造成的地表永久變位，是鄰近地下結構物需要關注的議題。臺灣都會區大眾運輸地下網路發展迅速，隧道的密度逐年增加，臺灣位於環太平洋地震帶，活動斷層多且地震頻繁，當強震發生時，會使隧道產生變形甚至是位移。若隧道位於活動斷層附近，近斷層效應以及地中剪裂帶發展亦會對隧道產生影響。此外，若都市進行更新計畫並進行新結構物的深開挖工程時，基地鄰近如有既存隧道，在地震發生時就需要探討隧道與剪裂帶之間的關係。
本研究是以離心模型模擬的方式進行，探討在傾角60度的逆斷層錯動下，矩形隧道在不同水平、垂直位置受到錯動時，隧道與剪裂帶的互制行為，而以下將以原型尺寸進行試驗內容的討論，試體之土層厚度為16 m的石英砂層，並於深度3.7 m、7.5 m處放置矩形隧道(以隧道中心點定義位置)，矩形隧道質心高度為1.86 m、接觸應力為56.8 kPa。本研究於試驗過程中紀錄斷層錯動量、隧道傾斜量、隧道位移量、剪裂帶發展與地表高程變化情形。本研究發現，當隧道埋深為隧道高度的2倍，且位於斷層延伸線上方或往下盤方向0.5倍隧道寬度時，隧道的傾斜量、水平及垂直位移量和地表影響範圍較大；而隧道距離斷層延伸線往上盤方向0.5倍隧道寬度或往下盤方向1倍隧道寬度時，這些影響較小，因此可定義出危險區域為距斷層延伸線往上盤方向0.5倍至往下盤方向1倍隧道寬度內。在相同埋置深度下，隧道距離斷層延伸線越近，傾斜量、水平和垂直位移量越大，最多增加17.6度、30.5%和36.3%隧道寬度。在相同水平位置下，埋置深度越淺，隧道傾斜量、水平和垂直位移量就越大，分別最多增加8.9度、5%和6.4%隧道寬度。隧道位於剪裂帶範圍內時，剪裂帶會繞過隧道，包絡線與延伸線角度最多增加37度（相同埋置深度不同水平位置）和10度（相同水平位置不同埋置深度）。剪裂帶與斷層延伸線的夾角越大，地表影響範圍越大，相同埋置深度下最多增加90%土層厚度，埋置深度變淺時最多增加40%。綜上所述，隧道設計需考慮埋置深度及水平位置對其穩定性及地表影響範圍的影響，以確保隧道安全。
;The permanent surface displacement caused by active fault movement is a critical issue for nearby underground structures. The rapid development of underground mass transit networks in Taiwan′s metropolitan areas has led to an increase in tunnel density year by year. Taiwan is located in the seismically active Pacific Ring of Fire, with numerous active faults and frequent earthquakes. When a strong earthquake occurs, tunnels can deform or even displace. If a tunnel is near an active fault, the near-fault effects and the development of shear zone in the ground can also affect the tunnel. Additionally, when urban renewal projects involve terminology for new structures, the relationship between existing tunnels and shear zones needs to be considered during an earthquake.
This study employs centrifuge model simulations to investigate the interaction behavior between a rectangular tunnel and a shear zone under a reverse fault movement with a dip angle of 60 degrees. The focus is on the tunnel′s response when subjected to fault movements at different horizontal and vertical positions. The prototype dimensions are discussed in the experimental content, with the soil layer composed of silica sand having a thickness of 16 m. Rectangular tunnels are placed at depths of 3.7 m and 7.5 m (defined by the tunnel center point). The tunnel centroid height is 1.86 m, and the contact stress is 56.8 kPa. During the experiments, fault movement, tunnel inclination, tunnel displacement, shear zone development, and ground surface elevation changes were recorded.The study found that when the tunnel burial depth is twice the tunnel height and located above the fault extension line or in the downward direction at 0.5 times the tunnel width, the tunnel′s inclination, horizontal and vertical displacements, and ground surface impact range are larger. Conversely, when located in the upward direction at 0.5 times the tunnel width or in the downward direction at 1 time the tunnel width from the fault extension line, these impacts are smaller. Thus, the danger zone can be defined as within 0.5 times the tunnel width in the upward direction to 1 time the tunnel width in the downward direction from the fault extension line. At the same burial depth, the closer the tunnel is to the fault extension line, the greater the inclination, horizontal and vertical displacement, increasing by up to 17.6 degrees, 30.5%, and 36.3% of the tunnel width, respectively. At the same horizontal position, the shallower the burial depth, the greater the tunnel′s inclination, horizontal and vertical displacement, increasing by up to 8.9 degrees, 5%, and 6.4% of the tunnel width, respectively.When the tunnel is located within the shear zone, the shear zone bypasses the tunnel, and the angle between the envelope line and the extension line increases by up to 37 degrees (at the same burial depth with different horizontal positions) and 10 degrees (at the same horizontal position with different burial depths). The larger the angle between the shear zone and the fault extension line, the greater the ground surface impact range, increasing by up to 90% of the soil layer thickness at the same burial depth and up to 40% when the burial depth becomes shallower.In conclusion, tunnel design needs to consider the impacts of burial depth and horizontal position on its stability and ground surface impact range to ensure tunnel safety. |
