粗糙節理模式於節理岩石順向坡之破壞分析

Abstract

順向坡為台灣常見之邊坡類型，其災變時常有快速的崩塌、滑動等現象，時常造成重大的災損。岩石邊坡中常有層面、葉理、節理等不連續面，這些不連續面往往為岩石邊坡穩定的關鍵。對於邊坡災害中常見的滑動破壞、塊體大量位移等問題，不連續面扮演著重要的角色，因此，透過能考慮分離塊體力學行為的離散元素進行順向岩坡之穩定分析，可望提供更準確之預測。 本研究應用分離元素法軟體PFC2D作為分析岩石順向坡之工具，透過邱家吉(2016)所提出之粗糙節理模式來闡述不連續面行為，進而分析節理岩石邊坡的破壞機制。研究將先以數值直剪試驗來驗證粗糙節理模式的合理性，接著透過模擬室內的研磨石直剪試驗，探討粗糙節理模式之適用性，最後以現地資料建立岩石順向坡模型，藉著與現地狀況的比對，探討其可行性。 在驗證粗糙節理模式的部分，將相同參數分別代入Barton力學模式及粗糙節理模式，分別得出Barton模式理論曲線及模擬數據，經結果的對比後，發現粗糙節理模式能合理的描述出Barton模式，使PFC2D能夠精確的描述弱面。而以粗糙節理模式模擬研磨石試體直剪試驗，同樣也得到良好的結果。最後以烏來忠治順向坡作為案例區，參照現地報告及鑽探資料，以節理遇水弱化及材料弱化做為促滑因子進行模擬，結果顯示，由兩種促滑因子的影響下，數值模型之崩積層有大量崩塌滑移的現象，而節理岩塊則有趨破碎的趨勢，與現地災後情形相符。由此可知，粗糙節理模式可用於模擬實際岩石邊坡，以供工程設計之參考。

There are many dip slopes in Taiwan. The failure of dip slope often has rapid collapse and sliding that causes significant casualties. Rock slope usually contains discontinuities such as bedding, foliation, joints, which are the key factor of rock slope stability. Thereforce, the discrete element analysis is a powerful method to investigate the stability of dip-slope. In this study, PFC2D software is choose as the discrete element method to analyze rock dip-slope. Use the rough-joint model which developed by Chiu (2016) to simulate the weak plane and then analyze the failure mechanism of rock slope. This study first verity out the accuracy of rough-joint model by numerical direct shear test, and then simulate laboratory direct shear test with artificial rock sample to investigate the applicability of this model. Finally, set up a numerical rock slope model with in-situ data and then compare it with practical condition to discuss about the application of the rough-joint model on rock slope failure analysis. In the part of rough-joint model verification, substituting the same parameter into Barton’s model and rough joint model can get a Barton’s theory curve and data of simulation. After comparison with each orther, we can find that rough-joint model can represent Barton’s model reasonably, and it let PFC2D express weak plane more precise. For the actual case-Wulai Zhongzhi, take the weakness of joints and rock material as sliding factor. The results of simulation are similar to practical condition and it indicate that rough-joint model can simulate rock slope well.