This study experimentally investigated the influence of number of joints on the mechanical behaviour of multi-joint samples during shearing under constant normal stiffness (CNS) boundary conditions. A series of samples that have different surface roughness and different numbers of joints are prepared, and the variations in shear stress, normal stress, normal displacement are analysed. The relationship between surface resistance index (SRI), defined as the ratio of shear stress to normal stress, and number of joints are estimated. The results show that with the increment of number of joints, the damage degree of the samples increases. For a multi-joint sample, the middle joint is most significantly damaged. When the shear displacement is small, the shear stress decreases with increasing the number of joints. However, when the shear displacement is large, the shear stress does not exhibit clear relationships with the number of joints. The SRI has clear peak values against shear displacement, and the peak SRI decreases linearly by increasing the number of joints, while the peak shear displacement increases following quadratic functions. Finally, two new regression functions are proposed to predict the variations in peak SRI and peak shear displacement for multi-joint samples during shearing under CNS boundary conditions.

中文翻译：

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剪切过程中包含多个平行节理的岩石样品的力学行为

这项研究实验研究了在恒定法向刚度（CNS）边界条件下剪切过程中，接头数量对多接头样品力学行为的影响。制备了一系列具有不同表面粗糙度和不同接头数量的样品，并分析了剪切应力，法向应力，法向位移的变化。估算了表面电阻指数（SRI）和接缝数量之间的关系，SRI是剪切应力与法向应力的比值。结果表明，随着接头数量的增加，样品的损伤程度增加。对于多关节样品，中间关节受到的损坏最大。当剪切位移较小时，剪切应力随着接头数量的增加而减小。然而，当剪切位移大时，剪切应力与接头的数量没有明显的关系。SRI具有清晰的峰值，抵抗剪切位移，并且峰值SRI通过增加接头数量线性减小，而峰值剪切位移随二次函数增加。最后，提出了两个新的回归函数来预测在CNS边界条件下剪切过程中多接头样品的峰值SRI和峰值剪切位移的变化。