正斷層錯動對地層應力以及微觀組構變化之影響初探

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Title:	正斷層錯動對地層應力以及微觀組構變化之影響初探
Authors:	李則辰;lee, tse-chen
Contributors:	土木工程學系
Keywords:	正斷層;離散元素法;應力場;剪裂帶;應力路徑;微觀結構;normal fault;discrete element method;shear band;fault offsets;Stress field;microstructure
Date:	2017-08-23
Issue Date:	2017-10-27 12:18:42 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究目的在探討正斷層剪裂帶附近到一定範圍內所造成的地表破壞行為及其底下的土壤力學機制。台灣位於板塊交界處上，因此地震的發生頻率很高，而且台灣地狹人稠，正斷層剪裂帶附近，可以觀察到許多因斷層錯動引致土層變形，但地表下的力學行為變化無法用肉眼看出。為了瞭解地表下的土層的應力場情形，我們利用了離散元素法來研究探討地表底下的應力變化，以後在近斷層區域土地利用上可以當作參考的準則。本研究使用了PFC2D來進行模擬，因為PFC (Particle flow code) 是以顆粒流來進行模擬，在力學行為上更能接近試驗砂箱狀況，在正斷層剪裂帶的上下方佈下觀測圓來探討斷層錯動時剪裂帶附近土壤的力學行為以及微觀結構變化。其結果指出，對於錯動期間的孔隙率變化，可以看出在下盤中，大多數孔隙率值沒有改變。對於剪裂帶附近的區域，在上盤區域（土層較淺的位置）中，孔隙率顯著增加。在靠近剪裂帶的底部區域（土層更深的位置），孔隙率略有增加。對於應力路徑與旋轉角的變化，在斷層剛開始錯動時，其應力路徑皆先側向壓縮接著再側向解壓回到初始值附近，變化值都在20kPa以內，而旋轉角變化皆在正負5°以內，代表遠離剪裂帶的應力變化值不大。但在剪裂帶附近兩旁區域的應力路徑，在剛錯動時是先軸向壓縮之後再軸向解壓，尤其是剪裂帶上方的區域，其應力路徑發展較為複雜。 ;This study is to investigate the surface failure behavior and the underlying soil mechanics mechanism in the vicinity of normal fault. Near the fault can be observed in the vicinity of the fault caused by a large number of soil deformation, but the mechanical changes under the surface can not be seen with the naked eye In this study, PFC2D was used to simulate, because PFC (Particle flow code) was simulated by particle flow, and the mechanical behavior was more close to the experimental sandbox. The measure circle was discussed in the upper and lower sides of the normal fault Mechanical Behavior and Microstructure Variation of Soil Near the Shear Zone in Faults. For the change in porosity during dislocation, it can be seen that most porosity values did not change in the lower panel. For areas near the shear zone, the porosity increases significantly in the upper plate area (shallow soil location). The porosity increases slightly in the bottom area near the shear zone (deeper in the soil). For the change of the stress path and the rotation angle, the stress path is compressed in the lateral direction and then decompressed in the vicinity of the initial value. The change value is within 20 kPa and the rotation angle changes in the positive and negative 5 ° or less, on behalf of away from the shear zone of the stress change is not significant. However, the stress path in the vicinity of the crack zone is axially decompressed after axial compression, especially in the area above the shear zone, and its stress path is more complicated.
Appears in Collections:	[Graduate Institute of Civil Engineering] Electronic Thesis & Dissertation

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