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標題: | 礫石層組構特性對逆斷層引致複合地層變形之影響 The Influence of Gravel Fabric on Deformation of Composite Strata Induced by Thrust Faulting |
作者: | Chien-Hui Hung 洪千惠 |
指導教授: | 林銘郎(Ming-Lang Lin) |
關鍵字: | 逆斷層,礫石層,複合地層,砂箱試驗,離散元素法,竹山槽溝五次斷層活動逆推, thrust faulting,gravel layer,composite strata,sandbox experiments,discrete element method(PFC3D),inversion of active faulting of Chushan trench, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 根據近年世界著名災害性地震之調查結果,顯示鄰近斷層帶結構物受到地震破壞之原因,除了激發強烈暫態的地震波之外,還有斷層基盤錯動所引致之近地表岩土層變形。過去關於活動斷層引致上覆土層的變形行為與結構互制之研究中,多將覆土材料簡化為圓球狀顆粒的砂層或黏土層,礫石層多變的組構並未被充分考慮。臺灣33條活動斷層中,有29條活動斷層的近地表有礫石層分布,從斷層帶附近之露頭觀察與斷層槽溝開挖,可以證實斷層基盤上覆非均質的複合地層是普遍存在的,且堆積礫石層中含有不同排列方向、不同形狀、不同尺寸的礫石。 本研究探討含有礫石層之複合地層受逆斷層錯動引致的變形行為,利用小尺度物理砂箱試驗與離散元素法數值模擬軟體(PFC3D)分別進行基本行為觀察與定量分析,物理砂箱試驗的成果亦用來校核數值分析中的所需的微觀參數。複合地層變形結果顯示,礫石層中的斷層滑動面傾角較緩且發展距離較小,地表影響範圍與三角剪切帶範圍往上盤擴大。礫石層的組構特性由不同體積含量、不同排列方式與不同長徑比的橢球形礫石顆粒所控制,高礫石體積含量與較大的長徑比使礫石層的斷層滑動面發展距離較小;高礫石體積含量以及礫石的長軸方向與斷層滑動方向愈不一致的情況下會讓三角剪切帶的範圍明顯往上盤擴大,礫石排列方式亦影響礫石最後的長軸方向。此外,礫石的轉動特徵指示了三角剪切帶範圍,具有長徑比的礫石可做為觀察礫石層變形行為的指標,且隨著基盤抬升比愈高,礫石旋轉的範圍往下盤擴大,旋轉角度持續增加。 從竹山槽溝剝片取得竹山槽溝的礫石層組構之後,進一步利用數值分析工具模擬了竹山槽溝北牆的變形演育,斷層滑動面發展順序、地質構造演變過程、礫石層變形前緣的礫石轉動情形、生長地層與地層侵蝕作用可被合理重現。 According to the investigations of well-known disastrous earthquakes in recent years, ground deformation induced by faulting is one of the causes for engineering structure damages in addition to strong ground motion. Previous studies which related to the deformation behavior of overburden soil induced by faulting and its impact on structures often simplify the overburden soil as spherical particles like sandy soil or clay, the complex fabric of gravel layer haven’t been fully considered. However, among the 33 active faults in Taiwan, there are 29 active faults with gravel layer distributed near the ground surface. Moreover, based on the trench excavation results in the fault zone, nonhomogeneous composite strata with gravel deposits in different arrangement, shapes and sizes overlay on the basement fault are common. A small-scale physical sandbox experiment and discrete element method numerical analysis(PFC3D) are conducted to figure out the basic behavior and do the quantitative analysis. Results from sandbox experiment are also used to calibrate microscopic parameters in numerical analysis. The deformation results of the composite strata show that the fault sliding surface in the gravel layer has a smaller dip angle and a slower development. The triangular shear zone in gravel layer is bigger that extends upward to the hanging wall. The fabric of the gravel layer are controlled by ellipsoidal gravel particles with different volume contents, arrangement and aspect ratios. Higher gravel volumetric content and the larger aspect ratio of gravels make the gravel layer more difficult to deform that developing a shorter fault sliding surface. The volumetric content and the arrangement of gravel mainly affect the range of the triangular shear zone, and the arrangement of gravel also affects the final deposition direction of the gravel. In addition, the rotation characteristics of the gravel indicate the range of the triangular shear zone, and the gravel with an aspect ratio can be used as an indicator the coseismic deformation behavior of the gravel layer. As the uplift ratio increasing, the rotation region of gravel expands into the footwall, and the rotation angle continues to increase. After obtaining the fabric properties of the gravel layer from the stripping of first excavation result of Chushan trench, a full scaled numerical simulation is conducted to identify the evolution of the north wall of the Chushan trench under repeated thrust faulting. The development sequence of fault sliding surface, the evolution of geological structure, the gravel rotation characteristics at the front of the gravel layer deformation, the growth strata and erosion can be appropriately replicated. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/8413 |
DOI: | 10.6342/NTU202001796 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 土木工程學系 |
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