山腳斷層位於台北盆地西緣,為一半地塹陷落之正斷層構造,覆蓋於台北盆地第四紀沉積物之下方(林朝宗,2001);在此沉積物上方有許多重要建設,若山腳斷層發生錯動,單層或多次沉積之上覆土層,將造成地表變形,並在變形區發展剪切帶,使結構物發生破壞。因此為了解斷層錯動時,覆土層對斷層剪切帶發展之影響,先以以數值方法模擬基盤錯動下,不同覆土層厚度剪切帶發展範圍之影響及地表差異變形之影響。再利用砂箱試驗了解山腳斷層生長次層(growth strata)之沉積現象,模擬覆土層之變形情況以及影響範圍。 針對無凝聚砂土之均質土層受斷層錯動之模型試驗,蔣佳興(2006)已有相當顯著之研究成果,本研究延續其砂箱及數值分析之方法學,主要分為山腳斷層之錯移量設計、山腳斷層全尺寸數值模擬以及生長斷層(growth fault)砂箱模型試驗。 由數值模擬之結果,可知剪切帶之發展受覆土層厚度之影響,覆土層厚度越厚則在相同之基盤錯移量下,塑性應變帶越不容易發展,對於地表之結構物影響越小;另一方面,當覆土層之厚度越厚,則在同樣之基盤錯移量下,元素與元素間之垂直位移差距較小,地表差異沉陷之情況較不嚴重。 由砂箱試驗之結果,顯示在砂箱試驗之分階錯動前後,原覆土層砂土層應力重新排列,對於剪切帶之發展無顯著之影響;另一方面,當正斷層含有生長層(生長斷層),則當基盤錯動時,剪切帶會沿原覆土層之剪切帶弱面向上發展,剪切帶會比單一覆土層,更為快速發展至地表。
Shanchiao fault is located in the west of Taipei basin, and the Quaternary sediments are above it. If the fault has an offset, the single overburden soil or growth strata will deform and cause shear zone. Definitely, the structures upon the overburden soil may cause some damages. So this study would like to know how the overburden soil deform and the inference of the area. By using numerical simulation, ABAQUS(finite element method), we can simulate different depth of Shanchiao fault. If we design a vertical displacement 2.5 m, we can observe the propagation of shear zone at different thick of overburden soil. The result of analysis shows that the thicker overburden soil will reduce the development of shear zone. By physical experiment, sandbox experiment, we can simulate the deformation of growth strata and the propagation of shear zone. The result of experiments show that the shear zone will propagate rapidly from the existed shear zone at footing wall.