以應力轉換法模擬橫向等向性岩石之力學行為

Using the methodology of stress transformation to simulate mechanical behavior of the transversely isotropic rock

葉家宏(Chia-hung Yeh)

指導教授 ： 田永銘

國立中央大學/工學院/土木工程學系/碩士(2008年)

摘要

過去在探討橫向等向性岩石力學行為，無論在試驗或是一般數值模擬，針對橫向等向性岩石方面，取樣後之岩石條件會不完全一致，使得不能確保在不同傾角是相同的岩石情況下來探討橫向等向性岩石力學行為，所得到的結果會是很令人質疑的，因此本研究為了克服過去在取樣後之岩石條件會不完全一致的問題，係以應力莫爾圓的觀念及應力轉換公式，來建立一套應力轉換法。應力轉換法利用FLAC有限差分程式來進行數值模擬，只需要相同模型的邊界上，來改變施加於模型邊界上正向力及剪力的應力增量，即可模擬各種傾角下的三軸試驗之過程，由於應力轉換法能夠達到模擬各種傾角下三軸試驗之過程是在相同岩石情況的目的，因此利用此方法來探討橫向等向性岩石力學行為的結果就會令人信服，所以本研究建立應力轉換法能夠提供另一種方法來探討橫向等向性岩石力學行為的研究。 本研究以應力轉換法模擬橫向等向性岩石之三軸試驗結果來做分析，並觀察多組不同橫向等向性岩石材料之模擬結果，進而認為橫向等向性岩石之性質以及岩塊含量是影響橫向等向性岩石整體工程性質的重要參數，並以合理的推估來建立有效預測各影響因素相互間的關係，最後本研究建立一套橫向等向性岩石力學行為預測模式，僅需要了解橫向等向性岩石之性質以及橫向等向性岩石內之岩塊含量，即可預測橫向等向性岩石力學行為，如此可以大幅減少試驗以及數值分析之時間，對於了解橫向等向性岩石力學行為的效率，必定大有助益。

關鍵字

橫向等向性岩石 ； 岩塊含量 ； 破壞準則 ； FLAC ； 應力轉換法

並列摘要

This research establishes a methodology of stress transformation by the concept of Mohr''s stress circle as well as the formula of stress transformation. This method can overcome the problem in the past research, which the rock condition will not be selfsame after taking samples in transversely isotropic rock. The methodology of the stress transformation makes use of numerical program (FLAC) to carry on the numerical simulation, that only needs to change stress increment of normal stress and shear stress on boundaries, which can create a series of triaxial tests in the same numerical model to investigate the mechanical properties of those transversely isotropic rocks in different types of dip angle formation. Therefore, it is convinced to make use of this method to probe into the result of mechanical behavior of the transversely isotropic rock.
This research utilizes the methodology of stress transformation, and observes the numerical results of different transversely isotropic rock materials. Furthermore, the rock material properties and volumetric fraction of block are important parameters to estimate mechanical behavior of transversely isotropic rock, and used to establish the prediction model of the mechanical behavior of transversely isotropic rock. The results show that the prediction agrees with numerical results, which can largely reduce the experiment as well as the numerical analysis, showing good improvement in prediction of mechanical behavior of transversely isotropic rock.

並列關鍵字

failure criterion ； FLAC ； transversely isotropic rock ； methodology of stress transformation ； volumetric fraction

參考文獻

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