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  • 學位論文

分離元素法山崩模型建置及震滑機制行為初探

Landslide model set up and simulation using discrete element method

指導教授 : 張國楨
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摘要


本研究以1999年集集地震所引發之草嶺山崩事件為例,運用數值地形模型(DTM)資訊,結合顆粒流分離元素之PFC 3D程式分析山崩之行為及機制。為決定山崩塊體及山崩影響範圍,分別運用災前、災後DTM來分析,並用以規範崩塌區之上、下部地形面,定義其間所夾空間即為崩塌之區塊。首先,本研究嘗試數種不同方法來建置崩塌區塊體及模型顆粒叢集等數值模擬之準備,包含NO SHADOW指令法、霣降法、三角柱法、重力排除法、顆粒汰選法等,比較各方法之優缺點及模型可行性等。本研究結果指出顆粒汰選法為最佳方法,其方法為依模擬岩石試體製作流程預先製作一含蓋整個崩塌塊體之顆粒匯集區,再將顆粒予以排除或汰選,配合施予顆粒元素間鍵結作用,進而建立一接近實際外幾何之形態、厚度之崩塌區塊,滑動面亦由DTM資料來建立,符合真實地形特徵之地表模型。 本研究考慮草嶺強震站之地震加速度資料,將之轉換為給定模型之地表地動速度,並考慮岩層中存在孔隙水壓所造成之影響,另考量岩層因受震產生高速滑移,並引致岩層摩擦係數弱化之影響。考量以上因素後,最後以簡化方式一併列入模擬之不同參數及相關模擬條件。 由模擬結果數據資料建置之DTM與真實DTM比對顯示岩層弱化後摩擦係數為0.087時可得最接近真實之堆積型態,其堆積區高程差平均值為-3.2m,樣本標準差為17.5。山崩發生之最大滑動距離為3662 m,最大落距高度為632 m,最高速度為87.2 m/s,本速度峰值之時間序列和地震訊號所得結果吻合。 研究成果顯示以三維離散元素顆粒流數值方法可模擬山崩發生之完整動態歷程,相較於一般常用之極限平衡法及有限元素法,除可求得破壞面及應力應變得知穩定性外,該方法還可模擬山崩發生之大變形行為,包含裂縫、運動軌跡、速度變化、滑動距離,乃至三維的堆積型態,進一步掌握災害發生之影響範圍。研究成果指示了本模擬之成效,以及震滑相關現象之推論。

並列摘要


This research takes Tsaoling landslide caused by Chi Chi Earthquake as an example, adopts from DTM data and also integrates the PFC 3D program of Particle flow discrete element method to analyze the sling mechanism and the landslide behaviors. To determine the affected area of landslide and to constraint the slid block, we use pre-disaster DTM and post-event DTM to build two topographic surfaces (upper topographic surface and lower topographic surface), thus the slid block between upper topographic surface and lower topographic surface could be defined. First of all, in this study several different methods are developed and tried to build the slidblock and the particle clusters to confine the slidblock, including NO SHADOW command Method, Pluviation Method, Triangular Prism Method, Gravity Elimination Method、Particle Detection Method, etc. The above-mentioned methods are compared according to the availability and feasibility. The Particle Detection Method is composed of several procedures: Firstly, prepare one dense and cubic particle clusters and then transpose to the mass center of the slid block; Secondary, the particle cluster should be rescaled in order to cover the entire slid block; Third, detect the particlesif the position is situated within the slid blocks confined by the upper and lower surface of the DTM before and after landslide, otherwise, the particle is been eliminated from the cluster. After the procedure, all there maining particles are bonded according to the material properties and served as the model for further landslide simulation. Therefore an almost realistic geometry concerning the thickness and shapes of slid block could be established, and the sliding surface also could be built from DTM data to match the real terrain features of topography. This study considers earthquake ground excitation by the strong motion acceleration data gather from the CHY080 seismostation situated just nearby the sliding area. Furthermore the existence of pore water pressure within the rock mass and the effect of friction coefficient attenuation caused by rock mass shaking and sliding are also integrated in this study. Compare the topography results from the simulation data with the real DTM, it says that the gained accumulation patterns of the simulation result could be mostly similar to real situation (DTM after landslide) at the friction coefficient of 0.087. The average difference between the DTM and PFC results is -3.2m and the standard deviation is about 17.5. When landslides occur, the largest sliding distance is about 3662 m, the maximum drop height is about 632m and the highest sliding speed is 87.2 m/s. The timing of maximum sling velocity coincides with seismograph of CHY080. The results shows that use the numerical method of three-dimensional discrete element particle flow can simulate the complete landslide process dynamically. Comparing with the limit equilibrium method and finite element method which are the most common to be used, the discrete element particle flow provides not only the states of instability but also the dynamical process of sliding. The result from this study states the effect of this simulation and states the inference of the related earthquake-sliding phenomena as well.

參考文獻


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被引用紀錄


周書玄(2013)。離散元素法初探材料微、巨觀參數之關係〔碩士論文,國立臺北科技大學〕。華藝線上圖書館。https://doi.org/10.6841%2fNTUT.2013.00249
張賀翔(2012)。應用分離元素法探討順向坡失穩歷程-以國道三號崩塌事件為例〔碩士論文,國立臺北科技大學〕。華藝線上圖書館。https://doi.org/10.6841%2fNTUT.2012.00385
林承翰(2014)。應用斜坡單元及分離元素法探討大型崩塌之演育〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2014.02495
鄭憲聰(2014)。應用分離元素法於台二線邊坡災害模擬〔碩士論文,國立臺北科技大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0006-2008201415522700

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