以分離元素法探討沉積岩順向坡 在滑動過程中內部應力的發展

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Title:	以分離元素法探討沉積岩順向坡在滑動過程中內部應力的發展
Authors:	謝政育;Hsieh, Jheng-Yu
Contributors:	土木工程學系
Keywords:	離心模型試驗;分離元素法;順向坡;應力路徑;centrifugal model;discrete element method;dip slope;stress path
Date:	2017-08-18
Issue Date:	2017-10-27 12:18:25 (UTC+8)
Publisher:	國立中央大學
Abstract:	台灣，位於環太平洋火山地震帶上的一個國家。由於地理位置特殊，在歐亞板塊與菲律賓板塊的相互擠壓下，使台灣成為一個山多平原少的地方。然而，每當地震、降雨過後，山區總會傳出一些坡地災害，再加上台灣特殊的地質環境，順向坡的滑動主要發生在於台灣西部山地丘陵地區的沉積岩層，這些順向坡在地震與豪雨的影響下，較容易發生滑動。尤其是砂頁岩互層的沉積岩由於兩者岩性的不同，水分無法滲透進頁岩層排出，層間孔隙水壓一旦升高會使得接觸面的剪力強度降低，最後會沿著層間滑開。本研究根據曾煒傑(2015)及林育槿(2016)進行的三組離心試驗模型來進行PFC3D的數值模擬：(A)層理角度與坡度均為30度的互層順向坡(B)層理角度60度且坡度為30度的互層順向坡(C)層理角度與坡度均為30度的厚薄夾層順向坡，在三組摸型中，會考慮坡趾砍腳和坡趾泡水軟化的條件下進行來進行的數值模擬，來觀察順向坡的滑動的行為。接著會利用離心模型試驗及數值分析相互驗證的參數，來探討不同坡高順向坡滑動可能的樣貌，最後透過本研究能夠瞭解順向坡在滑動過程中的力學行為。根據應力路徑的分析顯示，A組及C組順向坡的數值模型在滑動時，坡頂會有應力解壓的行為，而坡腹主要為受拉的應力狀態，在滑動時同樣會有應力解壓的行為出現。最後坡趾的應力路徑顯示，在滑動時會有垂直坡面方向的應力壓縮發展，隨著滑動的停止，會轉變為垂直坡面方向的應力解壓。B組順向坡模型的表面，隨著坡趾的隆起也會有相對應的行為發生，坡頂位置會是垂直層面方向的應力解壓，而坡腹和坡趾在坡趾隆起之前會是平行層面方向的應力壓縮，隆起之後則轉為平行層面方向的應力解壓。 ;Taiwan is an island where located at the Circum-Pacific Seismic Zone. In addition, the Philippine Sea Plate is pushed underneath the Eurasian Plate due to special geographical location. These may be attributed to the main reasons that have formed Taiwan as a mountainous country with complicated geological conditions. Moreover, the torrential rainfall accompanying typhoons frequently causes slope failures such as landslides and debris flows. The landslide of the dip slopes mainly occurs at the sedimentary rock layer of mountains and hills as observed at the west of Taiwan. Dip slopes of sedimentary rock are strongly affected by landslides due to natural disasters including torrential rainfall and earthquake. Moreover, some sedimentary rocks are alternated by different lithologies which contain sandstone and shale. Therefore water cannot infiltrate through the shale layer. As a result, the pore water pressure will increase and lead to the decrease in the shear strength between these layers. Finally, dip slopes will slide along the weaken zone as well as infiltration area. In this study, we discussed the deformation and stress behavior of the dip slopes with two kinds of models. First of all, the bedding plane is parallel to the surface of the plane which will be simulated in the first model. The second model shows that the inclination of slope surface is smaller than bedding plane. In order to further realize the dip slope failure, the landslide of dip slope with different thicknesses of the layers can be observed and estimated by centrifugal modeling test and PFC3D simulation. Basically, the test is performed under the condition of the toe of slope daylight and soaked in water. Moreover, we have to consider the buoyancy at the toe of the slope so that the numerical model can be closer to real conditions. Based on the result of the centrifugal model tests, PFC3D model was first verified through comparing with centrifugal models, and then adopted to simulate and determine the mechanism of dip slope model with different gravity fields. According to the results of the dip slope deformation, the stress paths showed different behaviors at each part of dip slope. In the first kind of model, the stress path showed stre
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