- 學位論文
利用岩芯室內試驗推求變質花崗岩場址現地應力之探討
Using laboratory rock core methods to estimate the in-situ stress at the Metamorphous granite area.
摘要
場址特性的描述為地下結構設計、天然資源開發與廢棄物地下儲藏的重要課題，包括地工特性、水文地質以及現地應力分佈等，皆為描述場址特性必需詳加調查、建立適當模型並評估特性參數的重要項目。其中現地應力的量測技術難度大、結果變異程度高，國內以往在場址調查作業階段較少納入，相關的調查結果與研究報導亦不多見。現地應力分佈的探查與應力場的確立，亟待積極展開。 本研究基於Stephansson and Zang (2010)提出的場址現地應力模型考量之架構下，利用變質花崗岩岩芯室內試驗，探求台灣花蓮和平地區現地應力分佈情況，並比較既有文獻報導的現地應力結果探討影響現地應力之因素，最終藉數值模擬探討斷裂等地質構造對現地應力分佈的影響。研究結果顯示，利用不同加卸載階段獲得的AE事件數與應變率差值，可研判預應力之方向與區間，進一步利用Yabe et al. (2010)提出的方法，可推估主應力之方向與量值。花蓮和平地區最大主應力方向在垂直向，約略等同於岩覆應力；水平向最大主應力方向在不同深度有所改變，研判可能係剪裂帶所引致。本研究繼而採用個別元素法分析軟體透過數值模擬探討斷裂等地質構造對現地應力分佈的影響，模擬結果顯示岩層發生錯移或斷裂後，斷層上盤與下盤之應力狀態會受破裂面影響而改變其應力值大小與方向，且斷裂等地質構造對現地應力分佈的影響範圍僅受限於斷裂面附近，不會影響到較遠的區域，但隨深度的增加，斷裂面發生的範圍變大，其對現地應力影響的範圍也會加大。
並列摘要
Descriptions of site characteristics are important to underground structure design, natural resource exploitation, and underground waste disposal. Geo-characteristics, hydrogeology, and in-situ stress distribution are critical items for describing site characteristics that should be investigated thoroughly, modeled appropriately, and evaluated for their representative parameters. Previously, in-situ stress measurement was rarely adopted by site investigations and relevant studies because such measurement is extremely difficult and shows high variability in the results. Stephansson and Zhang (2010) considered and suggested procedures and methods for the establishment of in-situ stress models for sites. In this study, we try to estimate the in-situ stress of Hoping area, Hualien, by using the laboratory granite rock core methods. And compare the measurement results of the other method, discussed the distribution characteristics and influencing factors of in-situ stresses measured at the studied site reported in literature. Finally by using numertical technique (PFC2D) to discuss the geological structures affect in-situ stress distribution. In addition, the azimuth and values of in-situ stresses were estimated based on the variations of acoustic emissions (AE) and deformation rate analysis (DRA) by Yabe et al(2010) considered. Research results indicate that the maximum principal stress in this area is inflicted along the vertical direction and has a magnitude similar to overburden stress. However, horizontal principal stresses measured at different depths show different results, which, upon preliminary evaluation, may be caused by sample anisotropy or shear zones. The results of distinct element simulation indicate that the dislocation or rupture of the geological structure (fault) will affect the in-situ stress distribution and the stress magnitude adjacent to the geological structure. Moreover, as the depth increases, the range of fractures occurrence becomes larger, and the influence area of the in-situ stress redistribution will also increase.