斜移斷層錯動引致上覆土層內結構物變形之研究

Investigation on the deformation of underground structures induced by oblique faulting

彭昱熙(Yu-Hsi Peng)

指導教授 ： 林銘郎

國立臺灣大學/工學院/土木工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202203524

摘要

2021年經濟部中央地質調查所公告全國共有36條活動斷層，許多活動斷層集中在人口密集、民生用水需求大的西部麓山帶及花東縱谷地區，因此像維生管線（水管、油管）、隧道等線型地中結構物多半較難避免跨越活動斷層。九二一地震災後，就曾出現多起斷層錯動引致輸配水地中結構物受損變形案例。過去關於活動斷層與地中結構物互制之研究中，多未考慮斷層平移分量所造成之影響，但諸多活動斷層皆具有三維斜向滑移的特徵，如再進一步考慮地中結構物與斷層相交關係，斷層與地中結構物之互制關係將變得更為複雜，衡量斜移斷層錯動引致上覆土層中結構物變形行為之難度也大幅提升。
本研究利用小尺度物理砂箱搭配有限差分法耦合離散元素法的三維數值模擬軟體（FLAC3D），探討斜移斷層引致地中結構物與上覆土層之互制行為。小尺度砂箱中，以地中結構物與斷層線之相交關係為變因，分析斜移斷層錯動下，斷層與地中結構物相交關係不同，引致地中結構物受力與上覆土層變形之特性，建立互制行為之基本概念，並利用物理砂箱實驗結果校核數值分析所用參數。最後透過1999年集集地震中石岡壩第二取水口輸水鋼管與石岡斷層互制之案例，確認耦合數值分析方法能合理應用於全尺度現地案例。
整合研究成果顯示，地中結構物會致使附近地表之破裂跡偏轉，地表亦會形成緩坡及陷落區之樣貌。當地中結構物順斷層平移方向佈設時，地表影響範圍雖會增加，但可減少結構物承受之彎矩。現地案例模擬顯示輸水鋼管變形狀況及地貌特徵與現地調查成果接近，結構物彎矩較大位置及地貌特徵亦與小尺度試驗趨勢一致。
綜合以上可知，地中結構物與斷層線之相交關係不同，與斜移斷層作用引致地中結構物受力及上覆土層變形密切相關，透過模擬現地案例，能推測結構物產生變形的位置，並於地中結構物設計中考慮調適策略，或可較能順應斷層作用。

關鍵字

斜移斷層 ； 上覆土層變形 ； 地中結構物 ； 上覆土層變形與地中結構物互制 ； 耦合有限差分法與離散元素法

並列摘要

In 2021, the Central Geological Survey（MOEA）announced that there are 36 active faults in Taiwan. Many active faults are concentrated in the foothills region in western and East rift valley, which are densely populated and have high demand for people's livelihood water. Therefore, life-saving pipelines（water pipes, oil pipes）are difficult for linear structures to avoid crossing active faults. For example, after the 1999 chichi earthquake, many structures in the water transmission and distribution system along the faults were squeezed and deformed. In view of this, how to ensure the safety of underground structures passing through the fault zone is a serious issue. In the past studies on the interaction between active faults and underground structures, the influence caused by the translational component of the faults was not considered for the most part. However, site investigations had found that many active faults had the characteristics of three-dimensional oblique slippage. If further consideration is given to the intersecting relationship between underground structures and faults, the behavior will become more complicated.
In this study, a small-scale physical sandbox was used with a three-dimensional numerical simulation software（FLAC3D）. Sandbox took the intersection relationship between underground structures and fault line as the variable factor to understand that the change of the force distribution of the underground structures and the deformation of the overburden soil layer. Also, establish the basic concept of the mutual behavior of the two. Finally, it is confirmed that the applies coupled FDM-DEM analysis method can be applied through a case of interaction between the water delivery steel pipe of the second water intake of Shigang Dam and the Shigang fault during the 1999 chichi earthquake.
The results show that the underground structures will deflect the rupture tracks, and the surface will also form the appearance of gentle slope and subsidence areas. When the underground structures are arranged in the same direction as the strike-slip direction, although the influence of the ground surface will increase, the bending moment of the structures can be reduced. The field case simulation shows that the deformation of the water delivery steel pipe is close to the field investigation results, and it can also be compared with the bending moment distribution of the small-scale test.
Based on the above, the intersecting relationship between underground structures and fault line is different and is closely related to the force of underground structures and the deformation of the overburden soil layer induced by the oblique faulting. Consideration of adaptation strategies in the design of underground structures may be more adaptable to faulting.

並列關鍵字

Oblique fault ； deformation of overburden soil ； underground structure ； soil-underground structure interaction ； coupled FDM-DEM approach

參考文獻

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