斷層錯動引致地表構造物與管線位移之模擬;Centrifuge modeling on the deformation of structure and pipeline by fault slipping

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Title:	斷層錯動引致地表構造物與管線位移之模擬;Centrifuge modeling on the deformation of structure and pipeline by fault slipping
Authors:	鍾承哲;CHUNG, CHENG-JHE
Contributors:	土木工程學系
Keywords:	正斷層;逆斷層;離心模型試驗;PFC2D數值模型;建築物;reverse fault;normal fault;soil strata;centrifuge modeling;PFC2D numerical modeling
Date:	2021-09-01
Issue Date:	2021-12-07 15:10:58 (UTC+8)
Publisher:	國立中央大學
Abstract:	自然沉積土壤是非均勻且非均質材料，斷層錯動過程中，剪裂帶會通過強度與特性不同的土層，活動斷層錯動多伴隨永久的地表變形，並損壞鄰近斷層之結構物與地下維生管線，為了避免上述災損，過去國內外已有正逆斷層錯動針對上覆砂層或黏土層的相關研究成果，並制定建築物的安全規範。本研究以離心模型模擬 60 度傾角之正、逆斷層錯動，通過總厚度 8 m之較高強度膠結砂土層與石英砂土層，兩土層厚度比為7:3，並於地表設置高 9.6 m、接觸應力為48 kPa、分別具有樁基礎與淺基礎之建築物，土層中埋設長 58.56 m、管徑 0.16 m之鋁管線以模擬維生管線。試驗過程中記錄錯動期間的剪裂帶發展、斷層錯動高度、建築物傾斜角變量與地表高程變化的關係。最後，進行數值模擬偶合，以離散元素程式PFC2D，透過離心模型試驗結果，驗證數值模擬的準確性。離心模型試驗結果顯示，在正斷層與逆斷層錯動狀況下，樁基礎建築物雖然會傾斜，但未發生翻覆；在錯動率 5 % 以下時，各試驗條件下建築物角變量皆超過1/100 之規定，建築物需要重建程度；具樁基礎建築物在正、逆斷層錯動率到達 50 % 時皆未發生翻覆，但具淺基礎建築物於正斷層錯動率 18.6 % 、逆斷層錯動率 46.0 % 時發生翻覆；在逆斷層試驗中地下管線的變形趨近於地表變形趨勢，正斷層試驗則因土層滑落使管線露出地表；具淺基礎建築物在逆斷層錯動時，地表變形的水平影響範圍約2倍的總土層厚度。以PFC2D進行數值模擬之前，需先以無圍壓縮試驗結果校正砂土層與軟岩層的設定參數，輸入參數可參考本研究之建議；以不同顆粒排列組成條件進行錯動模擬，會造成不同的剪裂帶發展結果；樁基礎勁度高於土層強度會造成建築物有較大的傾斜量與地表影響範圍。 ;Naturally deposited soil is a non-uniform and heterogeneous material. In the process of fault dislocation, the shear zone will pass through soil layers with different strengths and characteristics. Active fault dislocation is often accompanied by permanent surface deformation, damage adjacent fault structures and underground dimensions. In order to avoid the above-mentioned damages, there have been related research results on the overlying sand or clay layer of normal and reverse faults at home and abroad in the past, and the safety regulations of buildings based on these results have been formulated. In this study, centrifuge modeling tests were used to simulate the dislocation of normal and reverse faults with a 60 degrees dip angle, through a high-strength cemented sand layer and a sand layer with a total thickness of 8 m. The thickness ratio of the two soil layers is 7:3, and a building with a pile foundation or a shallow foundation was built on this surface. The height of this building is 9.6 m and the contact of pressure is 48 kPa. An aluminum pipeline with a length of 58.56 m and a pipe diameter of 0.16 m is embedded in the soil layer to simulate a lifeline. During the test, the relationship between the development of the shear zone, the height of the fault dislocation, the inclination angle of the building and the change of the ground surface elevation during the dislocation period was recorded. Finally, the numerical simulation is coupled to verify the accuracy of the numerical simulation through the results of the centrifuge modeling tests with the discrete element program PFC2D. The results of the centrifuge modeling test show that under the condition of normal and reverse fault, although the pile foundation building will tilt, it does not overturn. When the fault throw ratio is less than 5%, the building angle variable under each test condition exceeds 1 /100 stipulates which the building needs to be rebuilt. Besides, the building with piled foundation has not overturned when the fault rate of normal and reverse fault reaches 50%; however, the building with shallow foundation has overturned when the fault rate of normal fault is 18.6% and the fault rate of reverse fault is 46.0%, respectively. In the reverse fault test, the deformation of the underground pipeline has a trend toward the surface deformation, while the normal fault test causes the pipeline to be exposed to the surface due to soil slippage. When the reverse fault is dislocated, the surface of affected zone is about 2 times the total soil thickness. Before using PFC2D for simulation, it is necessary to calibrate the setting parameters of the sand and soft rock layers with the results of the unconfined compression test, which can refer to the suggestions of this research. The simulation of the dislocation with different particle arrangement and composition conditions will cause the different of the development result of the shear zone. Lastly, the stiffness of the pile foundation building is higher than the strength of the soil layer, which will cause the building to have a larger amount of inclination and the range of influence on the ground surface.
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