节理的剪切强度涉及到岩体工程的安全。通过CSS–342岩体剪切试验机对3组具有不同形貌特征的节理进行直剪试验，研究形貌对剪切强度的影响。试验结果表明：峰值剪切强度随法向应力和粗糙程度的增加而增加；但就相同的形貌而言，剪切应力与法向应力的比值减小，即由形貌产生的剪胀角随法向应力的增加而减小。通过分析剪胀角存在的边界条件，提出双曲线形式的剪胀角演化模型，并采用抗拉强度体现岩石的性质对节理剪切强度的影响。采用坡度均方根表征节理的三维形貌特征并提出相应的峰值剪切强度公式，与经典的Barton公式进行了比较，总体上新公式的计算值更为接近试验值。

The shear strength of rock joint is the basis information to assess the response and safety of rock engineering in practice. Using the rock shear machine CSS – 342, a series of tests has been made on artificially cemented rock joint samples with varied morphology to investigate the influence of surface morphology on its shear strength. It can be easily found that the peak shear strength increases with increasing the normal stress and roughness. However, in the case of same surface morphology, the ratio of shear stress to normal stress decreases with increasing normal stress, indicating that the dilatancy angle caused by the morphology decreases with increasing normal stress. A hyperbolic function is proposed to describe the evolution of dilatancy angle under varied normal stress on the basis of a detailed boundary condition of dilatancy angle. In the current research, the tensile strength is used to capture the effect of intact rock. Then, a new empirical formulation is suggested to evaluate the peak shear strength of rock joint by using the slope root mean square. A comparison between the proposed empirical criterion and the famous Barton formula is also made. The results indicate that the calculated values by the proposed criterion are in good agreement with the measured ones.