Development and Application of Discontinuum Model on Jointed Rock Masses(II)

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Project title

Code/計畫編號

NSC98-2221-E019-042

Translated Name/計畫中文名

岩盤工程非連續體模式之研發與應用(II)

Project Coordinator/計畫主持人

Cheng-Yu Ku

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Department of Harbor and River Engineering

Website

https://www.grb.gov.tw/search/planDetail?id=1913216

Year

2009

Start date/計畫起

01-08-2009

Expected Completion/計畫迄

31-07-2010

Bugetid/研究經費

498千元

ResearchField/研究領域

土木水利工程

"台灣地區由於受到板塊擠壓，造就出陡峻的地形與脆弱多變的地質環境，破碎之地層造成斷層、層面、節理、張裂縫、或剪裂縫等弱面幾乎無所不在，而這些弱面係主控岩盤之力學行為，使得岩盤工程問題分析有別於傳統以連續體觀念之分析方法，必需另行考慮岩體內弱面之接觸碰撞之力學行為，而較為複雜。對於破碎岩盤而言，分析域內所包含之不連續面可能由數組至無限多組等，過去對於極為破碎之岩盤時，多以等效連續體之概念之觀念加以概括分析，但對於主控之構造，諸如：斷層或是剪裂帶等，等效連續體之分析有其限制。不連續體之分析方法將分析域視為各個不連續岩石塊體之組合，塊體與塊體間之元素為可分離，其亦可考慮塊體間接觸與碰撞之力學特性，對於斷層構造等之不連續面具有分析大變形能力之優越性。自集集地震後，岩盤受到劇烈擾動而非常破碎，近幾年來數次的颱風事件，經常導致山區發生大規模的山崩與土石流，導致各地的受災範圍與程度均遠較過去為烈，嚴重地危害到民眾生命與財產的安全。傳統以連續體觀念發展之分析方法對於台灣地區如此破碎之岩盤問題分析其適用性受到相當之侷限，諸如中部地區大甲溪流域嚴重之崩塌、落石與土石流問題，或是邊坡發生崩塌後，其崩塌材料之移動範圍與可能影響範圍等，均是目前亟待解決之問題，因此針對裂隙岩體問題發展合適台灣地區之非連續體分析模式有相當之必要性。另台灣地區近年來大力推動生態工法，使工程與自然相互融合，生態工法中之砌石及預鑄塊堆疊構造物具有塊體堆疊、多孔透水、材質重及塊體間不連續之特性，目前已大量使用於野溪整治，惟數次颱風事件亦發現為數不少之砌石構造物損毀，進一步發展合適之不連續體之分析方法以克服一般傳統分析方法對不連續之塊狀結構變形行為分析之限制，並釐清砌石間之不連續界面在承受荷重後應有之高滑動潛勢，亦有其相當之必要性。本研究計畫第一年發展以不連續變形分析法為理論之分析方法，除修改理論與分析方法之相關限制外，並進一步推導理論與撰寫分析程式，建立顆粒版本之不連續變形分析法理論與分析程式，目前已完成相關理論與分析程式撰寫。第二年擬將流體機制與不連續變形分析法進行結合，並推導流體機制與不連續塊體顆粒間之力學互制關係，之後再將本研究所建立之理論與分析程式應用於土石流問題與生態工法砌石構造物之模擬分析。第三年將以第一年與第二年之研究成果為基礎，進行裂隙岩體問題之分析研究，研究方法擬進一步將不連續變形分析法之理論與有限元素分析方法加以結合，故不連續塊體除可進行大位移外，塊體本身之變形性亦可加以考慮，因此可分析諸如山崩或是地滑等沿著明顯弱面發生滑動之現象，第三年研究之成果預期將可模擬邊坡由初期不穩定之變形分析至後期邊坡發生破壞滑移後之後邊坡塊體產生大位移之行為。" "Taiwan is an active mountain belt created by the oblique collision between the northern Luzon arc and the Asian continental margin. The inherent complexities of geological natural creates numerous discontinuities through rock masses in this area, which exist in many forms such as fissures, cleavages, beddings, joints, and even faults and dominate the behaviour of jointed rock masses. Modeling the response of jointed rock masses is a daunting task because of the presence of inherent discontinuities. The continuum approach uses mainly the finite element method as the backbone. It relies either on the adoption of an equivalent continuum for a jointed rock mass, or on treating discontinuities as added interface. An equivalent continuum approach lacks the capability in capturing the overall kinematics of a jointed rock mass from discontinuities. The discontinuum approach, on the other hand, considers a rock mass delineated by joints as blocks, and is capable of capturing of kinematics of the block system. It demonstrates a great potential in modeling the jointed rock mass problems. In recent years, the increase in the frequency and intensity of extreme natural events due to global warming or climate change brought significant landslide and debris flow hazards. The Chi-Chi earthquake and the following several typhoon events in particular triggered hazards including landslides, debris flows, and floods which caused significant property damage and inflicted heavy casualties. Accordingly, the study on the development of discontinuum model for dealing with the landslide and debris flow hazards is essential. In addition, considering both ecology and safety in engineering constructions, the government had devoted great effort on promoting the Ecological Engineering Method (EEM) in the recent year and achieved many engineering works featured with the beauty of nature of Taiwan. However, the mechanical analyses of various EEM structures have not been investigated yet and more study on this aspect seems necessary and urgent. To resolve the problems mentioned above, a 3-year project was proposed herein. The first year is to develop a particle version of the DDA method as well as to establish the numerical DDA code. Based on the achievement of the first year project, the second year is to develop the couple analysis of fluid and mechanics in DDA method. This enables the possibilities of the simulation of debris flow problem by using the DDA method. In addition, the mechanical analyses of EEM structures will also be discussed. Based on the achievement of the first and second year projects, the third year is to develop the NMM method by combining the DDA and FEM methods. Groundwater effects on joints, and contact modeling for simulating the process of a slope failure using the NMM will be studied in this year. The study is to pursue the possibility for developing a NMM code with capable of capturing an entire process of a slope failure evolution from the initial phase, to the intermediate phase, and to the final post-failure phase of a failed block sliding down the slope."

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Development and Application of Discontinuum Model on Jointed Rock Masses(II)

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