Simulation of the Influence of Rock Quality to the Stability of Tunnel Excavation using Finite Difference Method

[[abstract]]1954年人類首次用核反應爐產生出了電能 核能就被視為是一種新發現的替代能源，而且如果用它取代化石燃料來發電的話，全球溫室的效應也會因而減輕 但也因此產生了核廢料的最終儲藏和處置的另一項艱巨挑戰。由於核廢料具有放射性，它必須完全阻隔於人類的生活圈，而深層地質處置(Deep Geolgic Disposal)方式為目前世界各國公認永久處置該放射性廢棄物最有效的方法。 本研究以核廢料深層地質處置概念進行了三維之有限差分法(Finite difference Method)數值分析，藉由美國ITASCA公司在1997年開發之FLAC3D（Fast Lagrangian Analysis of Continua in 3 Dimensions）軟體針對處置場主隧道掘進與處置孔交叉段開挖過程所產生力學行為之影響進行數值模擬與分析。本研究將岩體的力學性質假設為彈性-完全塑性材料（elasto- perfectly plastic material）並且符合Mohr-Coulomb破壞準則，在處置場的穩定性的分析上則分別選取側向壓力係數K=1的不同岩體品質條件RMR下進行參數的靈敏度分析。 本研究所獲得之成果說明如下：(1)建立利用FLAC3D獲取隧道掘進過程中岩石之變形與應力變化行為之能力。(2)進行在貯置場中主隧道與處置孔交叉段岩石之應力與應變重新分配及應力集中現象的探討。(3)本研究完成在不同的岩盤等級RMR下於重要斷面位置的三維數值模擬變位分析，其結果可直接的應用到未來隧道的現場施工與設計。(4)對於目前部分岩石力學中屬於概括性之經驗法則，可利用本研究所獲取岩石之應力與應變數值分析結果進行探討。[[abstract]]The electric power generated from nuclear reactors was initially implemented in 1954 The nuclear energy therefore has been treated as a newly discovered alternative energy since then The global greenhouse effect can then be reduced However a huge challenge to final storage and disposal of the nuclear waste was generated The nuclear waste has to be completely isolated from the human life circle due to its release of radiation Currently the deep geological disposal method for the final disposal of the nuclear waste is treated as the most effective method In this research a 3-D numerical analysis was conducted on the concept of the Deep Geologic Disposal method for nuclear waste using the FLAC3D（Fast Lagrangian Analysis of Continua in 3 Dimensions）software originally developed by the US ITASCA Company in 1997 The numerical simulation and its analysis focused on capturing the influence of the mechanical behavior at the intersection of deposition tunnel and disposal holes during the construction period The mechanical properties of rocks employed in this research were assumed as a elasto-perfectly-plastic material following the Mohr-Coulomb failure criterion The stability analysis includes the parametric sensitivity study of the disposal site with a variety of rock quality expressed by RMR and coefficients of lateral pressure K=1 The numerical results obtained from this research can be summarized as follows (1) The ability of capturing the behavior of the variation of stress and strain in rocks due to tunnel excavation using FLAC3D has been established (2) The study of the redistribution and concentration of stress and strain of rocks in the main tunnel and tunnel intersection has been implemented (3) The 3-D numerical displacement analysis in rocks with various RMR values in critical positions has been accomplished The obtained results can be directly applied in tunneling construction and design in the future (4) The related general empirical rules in rock mechanics can be studied with the numerical results of the stress and strain in rocks obtained from this researc