由於岩體中常伴隨節理面構造，因此使得岩體整體剪力強度不止受到岩體本身材料強度之影響，同時也受到節理面存在而可能有變化。岩石節理面之存在對於岩體剪力強度之影響，已有Barton提出之公式可推估岩體受節理面影響下之剪力強度，其中節理面粗糙度為重要之影響因素，且通常用節理面粗糙度係數(簡稱JRC)來表示岩體節理面剖面之粗糙程度。Barton(1977)提出之視覺對照法為最早評估岩石節理剖面JRC的方法，但由於此方式較為主觀，因此近年來許多學者提出了數值量化的客觀方式來評估JRC，如利用剖面線段長度的方均根值Z2、碎形維度D，或利用線段角度的傾角擬合參數C等，希望能夠更客觀的評估JRC值。
廖明傑(2016)蒐集並數位化86條岩石節理剖面(已知JRC)，並對其進行統計分析，發現其剖面節理面的高程差呈現常態分佈，且其高程差之標準差與JRC值具有高度相關性，並藉由上述岩石節理面剖面之統計參數，隨機生成了一千組新的岩石節理剖面。本研究利用離散元素軟體PFC2D建立岩石節理面之直剪模型進行直剪試驗之模擬，分別對不同JRC所隨機生成之岩石節理剖面建立直接剪力試驗的數值模型，藉由此數值模型所得的結果與Barton(1977)提出之剪力強度經驗公式進行比較。
除了針對不同JRC區間的岩石節理面模型進行直剪試驗之模擬，與Barton所提出之經驗公式進行對比，我們利用石膏模型進行實際的直剪試驗，以此和模擬之結果進行對比。

Because the rock mass is often accompanied by the joint, the overall shear strength of the rock mass is affected not only by the strength of the material itself, but also by the existence of the joint. The influence of the existence of rock joints on the shear strength of rock mass has been proposed by Barton to estimate the shear strength of rock mass under the influence of joint. Where the joint surface roughness is an important influencing factor, and the joint roughness coefficient (JRC) is usually used to represent the roughness of the section.
Barton (1977) proposed the visual comparison method for the earliest assessment of the JRC method, but because of this approach is more subjective, in recent years, many scholars have proposed numerical quantitative objective way to assess JRC.
We use the PFC2D to simulate the rock joint model of the direct shear test. The numerical model of the direct shear test was established for different JRC of the randomly generated rock joint. The results obtained by this numerical model are compared with the empirical formula of shear strength proposed by Barton (1977).
After that, we simulate the direct shear test of the rock joint surface model for different intervals of JRC and compare the result with the empirical formula proposed by Barton. In addition, we use the plaster model for the actual direct shear test, and compared with the simulation results.

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