山谷崩坍模擬堆積體之顆粒分佈與孔隙率

機構典藏 > College of Engineering > Graduate Institute & Department of Civil Engineering > Thesis > Item 987654321/74496

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Title:	山谷崩坍模擬堆積體之顆粒分佈與孔隙率
Other Titles:	Study on the grain distribution and porosity of landslide mass in a valley model
Authors:	鄧芸浩;Dung, Yun-Haw
Contributors:	淡江大學土木工程學系碩士班楊長義
Keywords:	天然壩;Landslide dams;堆積體;顆粒分佈;谷型;孔隙率;Mass;Grain distribution;Valley;Porosity
Date:	2011
Issue Date:	2011-12-28 18:44:45 (UTC+8)
Abstract:	堰塞湖的壽命及壩體潰決方式與崩塌堵江之岩屑或土砂的材料特性有關，如壩體透水係數與壩體強度，而天然壩體的強度及透水性則與其組成壩材之顆粒分佈有密切相關性。由文獻可知：天然壩體的組成顆粒大小變化範圍極大，且天然壩體上部常具一粗顆粒或碎石組成的外殼，底部組成顆粒卻是極細小，故天然壩體各部位力學性質是不均質，其顆粒大小成分及堆疊排列方式有關。本研究利用V形斜坡儀器模擬山谷地形，藉由改變粒徑、坡度與距離等不同影響因子，施做邊坡崩坍堆積試驗，將堆積體採凝固處理，分塊取出拍照得剖面圖做影像分析，最後對堆積體做力學試驗。研究結果得致以下幾點結論： (1)安息角不因試驗方式差異而有明顯不同，顆粒數量應超過某一定顆數安息角才較趨於固定。且谷底形狀並不影響最終維持崩落堆積體的自然穩定之安息角度大小。(2)山谷崩落堆積過程，顆粒滾落至谷底後常再撞擊到對岸而反彈折回來覆蓋堆積於堆積體之上或與後下來顆粒一起堆積。所形成的天然堆積體，因經歷動態夯壓效果，其邊坡穩定性高於靜態安息角。其中依序長落距、陡邊坡與粗顆粒是影響堆積體坡度主因。(3)堆積體孔隙率隨著滑動距離增加而略為減小，細顆粒含量越高孔隙率也會越小。並透過影像分析與篩分析得知堆積體粗顆粒多聚集於上層，細顆粒在下層。但滑動距離增加則堆積體內粗細顆粒分佈會較均勻。(4)堆積體因上下層孔隙率不同，應用於真實天然壩體滲透性分析，有別於傳統單一滲透係數，上下分兩滲透係數對滲流量計算公式修正，發現與傳統單一滲流量略有差別，可供日後預估潰壩時間參考。 The lifetime and dam breach modes of landslide dams are related to the material characteristics of the rock debris or the sediment which collapsed to block rivers, for example, the permeability coefficient of the dam and dam strength, and the strength of natural dam and their permeability are closely related to particle distribution of the dam material composition. According to literature, the particle sizes of dam material composition vary greatly, and the upper part of natural dams often contains a shell made of coarse particles and gravels, the bottom is composed of very fine particles. Thus, the mechanical properties of various parts of natural dams are not uniform, they are related to particle sizes, composition and mode of stacking and arrangement. This research used the v-shaped slope apparatus to simulate the valley terrain. Tests of slope collapse accumulations were carried out through changing the various influencing factors such as particle sizes, slope, and distances. The accumulations were treated with solidification. Blocks of materials were removed to take photos to build a profile for imaging analysis. Finally, a test of mechanics was performed on the accumulations. The following conclusions have been obtained through the research results: (1) The angle of repose did not show a significant difference due to different testing methods, the angle of repose became more gradually fixed after the particles exceeded a certain count. The shape of valley bottom does not affect the naturally stabilized angle of repose to maintain the final landslide mass. (2) In a valley landslide process, after the particles fell to the valley bottom, they often hit the other side and bounced back to cover the landslide lass or mixed with the particles that came down later. Because the natural landslide mass formed went through the dynamic compaction effect, its slope stability is higher than its static angle of repose. The primary factors in order of significance that affect the slopes of landslide mass were long drop distance, steep slope, and coarse particles. (3) The porosity of landslide mass reduced slightly as the sliding distance increased, the higher the fine particle count the lower the porosity. In addition, it was found out through imaging analysis and sieve analysis that the coarse particles of landslide mass were mostly located in the upper layer, and the fine particles in the lower layer. The distribution of coarse and fine particles became more uniform as the sliding distance increased. (4) The porosities differed between the upper and lower layers in the landslide mass. When applied in the analysis of permeability of natural dams, it differed from the traditional single permeability coefficient, the correction made to the calculation of seepage volume due to the upper and lower permeability coefficients caused a somewhat different result from the traditional single seepage volume. This can be used as a reference to estimate the dam breach time in the future.
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