以離心模型模擬正斷層及逆斷層通過複合土層引致的地表變形特性

張庭傑(Ting-Chieh Chang)

指導教授 ： 李崇正

國立中央大學/工學院/土木工程學系/碩士(2014年)

摘要

臺灣位於地震頻繁的環太平洋地震帶，人口密布且房屋林立，自來水、電力及瓦斯等維生管線系統分佈廣泛。當斷層發生錯動時，若產生較大的地表破裂或地中土層變形，會對週遭的建築物帶來危害，諸如道路斷裂、橋梁倒塌、停電及瓦斯外漏等。欲降低地震時斷層錯動所帶來的災害，最直接的方法就是避免將建築物蓋在斷層附近，然而臺灣地狹人稠且可利用土地較少，建物時常無法避免鄰近斷層錯動帶。為確認錯動區建築物的安全性，以及該區工程用地之可能性，瞭解斷層錯動引致的地表、地中土層變形特性，還有斷層與地工基礎間的互制作用是一重要的課題。本研究使用試驗土樣為皂土拌合甘油而成的人工黏土，人工黏土所使用的含油量(g/c)為34%與含油量(g/c)為40%兩種，以及306號石英砂，係屬不良級配之砂樣。利用70g離心模型試驗模擬斷層錯動，以瞭解斷層通過黏土砂互層之影響範圍及土層之變形特性，且離心試驗之結果可供數值分析做對照，並搭配觀景窗攝影機即時觀察斷層錯動的變形與斷層跡的發展。試驗結果顯示：(1)黏土砂互層之逆斷層試驗的影響範圍除以覆土層厚度所得之正規化值最大約0.96，均小於黏土砂互層之正斷層試驗的最小正規化影響範圍1.04；(2)純砂層與黏土砂互層的正斷層試驗，上盤向下滑動導致斷層空隙產生，為填補錯位造成的空隙因而產生地塹的現象；(3)逆斷層試驗中，純黏土層的地表無明顯裂縫，但在黏土砂互層中，則產生較寬的裂縫；(4)黏土砂互層之黏土層，因厚度較純黏土層薄，性質相對較於脆性，正斷層錯動時易造成地層斷裂，形成斷崖。

關鍵字

離心模型試驗 ； 斷層 ； 斷層跡 ； 複合土層

並列摘要

Taiwan locates at the Circum-Pacific seismic zone and there are 33 active faults in this small island. Earthquakes occur frequently and the slip of fault causes the ground surface deformation leading to the damage of buildings, bridges and lifelines, especially for the west-Taiwan with dense population. The behavior of fault rupture propagation is not well known and involves with many parameters, such as thickness and strength etc. In this study, an artificial clay was used by mixing the bentonite and glycerol and a fault simulation container with acrylic window was used to observe the propagation of shear zone within the soil stratum and the ground surface deformation. Six centrifuge modeling tests were performed at 70 g acceleration field to investigate the development of fault rupture through sand and clay interlayers.
The test results show that (1) the maximum normalized effect length of clay-sand interlayer deposit caused by reverse fault is 0.96H, where H is the thickness of soil deposit. On the other hand, the minimum normalized effect length of clay-sand interlayer deposit caused by normal fault is 1.04H. The effect length of reverse fault is smaller than that of normal fault. (2) The graben is caused by the stuff void and observed in the normal fault tests of both sand and clay-sand interlayer models. (3) For the reverse fault tests, the tension cracks on the ground surface is observed significantly in the clay-sand model, and crack does not occur on the surface of the clay model. (4) The thickness of clay layer in clay-sand model is half of that in clay model. The thinner clay layer shows the relative brittle behavior and it is easy to form the cliff at the ground surface.

並列關鍵字

centrifuge modeling test ； fault ； fault rupture ； interlayer

參考文獻

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