逆斷層錯動下土層應力場受淺基礎載重及位置之影響

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题名:	逆斷層錯動下土層應力場受淺基礎載重及位置之影響
作者:	邱威智;Chiu, Wei-Chih
贡献者:	土木工程學系
关键词:	逆斷層
日期:	2019-01-28
上传时间:	2019-04-02 14:08:52 (UTC+8)
出版者:	國立中央大學
摘要:	台灣位處於歐亞大陸板塊與菲律賓海板塊之交界，所以在進行工程設計，經常要考慮地震的作用，特別是位於活動斷層附近的區域，必須更加留意斷層錯動造成的破壞，近年來，如台灣集集大地震、土耳其Izmit 地震、中國汶川大地震、日本福島大地震等活動斷層造成的災害，均使生命財產遭受到嚴重的損害。通常在較大地震過後的現場可以發現，結構的傾倒或是變形，主要受到斷層錯動造成地表變形的影響。藉由觀察斷層錯動和基礎位移或變形下的互制關係，可以發現斷層破裂路徑似乎會轉向，進而避免結構的破壞。因此近幾年來有許多研究考慮使用有限元素法(Finite Element Method, FEM)與離散元素法(Discrete Element Method, DEM)等數值方法進行模擬，然而斷層錯動往往達到數公尺，當斷層變形過大時，有限元素法網格會造成較大的變形，所以在本研究中為了得到較精確的結果，考慮使用離散元素法進行逆斷層模擬。研究中，參考張有毅(2013)砂箱試驗之離心模型試驗，使用 PFC2D(Particle Flow Code in Two Dimension)在80g 下進行淺基礎與斷層的互制關係模擬，其斷層最大垂直位移(h)為5cm。模擬中所採用的變因包括:(1)基礎的載重大小和(2)基礎相對自由場的出露距離大 II 小，然後利用這些變因來探討淺基礎與斷層互制關係的原因。首先藉由顆粒的旋轉角來判斷基礎在逆斷層錯動下剪裂帶的發展狀況，然後探討基礎相對自由場的出露距離大小與基礎的載重大小兩種變因，這兩種變因比較基礎在逆斷層錯動下剪裂帶的發展長度對基礎影響大小；近一步得知應力在模型中不同位置的變化，按照深度分成淺、中、深三層，再依照位置分成上盤、過渡區、下盤三個區域，依此原則設置觀測圓讀取數據，再將最後模擬結果藉由應力路徑，探討基礎相對自由場的出露距離大小與基礎的載重大小兩種變因，這兩種變因比較基礎在逆斷層錯動下土層應力場發生破壞的狀況，藉由應力路徑的分析了解基礎在逆斷層錯動下土層發生破壞的過程；由剪裂帶的發展狀況及應力場的變化可以比較出兩個變因的影響大小。;Taiwan is located between Eurasian plate and Philippine sea plate, so the effect of earthquake must be considered in the engineering design. The area close to the active fault must be paid more attention to the damage from the fault rupture. In recent years, events such as the Chi-Chi earthquake, Izmit earthquake, Wenchuan earthquake and Fukushima earthquake caused serious damages to the structures and lives. After the earthquake, the propagation of reverse faults through soil layers to the ground surface has been observed to cause damages to infrastructure. Furthermore, the interaction between a fault propagating through a sand layer and a shallow foundation can be beneficial for heavily loaded foundations because this loading condition can deviate fault away from the foundation. In this research, we have used the models in Chang (2013) as base models, in which centrifuge modelling of fault–foundation interaction was simulated. The tests revealed interaction between fault and foundation and found that the foundation and soil response depend on the foundation loading, position, and breadth. To observe the variation of stress states in different location within the soil layers with different parameters, the model is separated into shallow layer, medium layer and deep layer in the vertical direction, and divided into three zones depending on the horizontal location (hanging wall zone, triangular shear zone and footwall zone). Measurement circles are placed in the model to measure the stresses according to the above zoning and the results are shown by stress paths. The results show that compression between footing wall and hanging wall affects the development of horizontal stress obviously, it increases the values of horizontal stress. Finally, the effect of foundation location and loadings are discussed by the development of shear zones and stress paths.
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