考虑剪切方向的改进Barton模型

为研究节理在剪切过程中的方向性和剪切强度规律，利用直剪仪对复制岩石节理试样进行了爬坡和顺坡两个方向的直剪试验。试验结果表明：剪切方向对岩石节理的剪切强度有明显影响，沿爬坡方向的剪切强度大于沿顺坡方向，但粗糙度系数（joint roughness coefficient，JRC)的减小和法向应力的增大可在一定程度上削弱剪切方向的影响。节理剪切破坏过程具有显著的阶段性特征，中低法向应力条件下以爬坡滑移为主要机制，而高法向应力下以相互啃食和凸起啃断为主要机制。采用平均有效倾角差指标参数描述剪切强度的各向异性，并在此基础上提出了考虑剪切方向的改进剪切强度模型，更好地预测节理正、反方向的剪切强度。通过百分位数参数建立了三维形貌指标与端部轮廓线二维高差指标的联系，大大简化了节理形貌指标的获取难度。该模型参数较少容易获取，物理意义明确，且把岩石节理剪切强度的各向异性考虑在内，具有广阔的潜在工程应用前景。

Improved Barton Model Considering Shearing Directions

In order to investigate the law of the shear anisotropy and strength of rock joints in the process of shearing, samples were tested with direct shear apparatus in climbing and downhill directions. The test results show that the shear direction has an obvious effect on shear strength. The shear strength in climbing direction is greater than that in downhill direction, while the decrease of JRC (joint roughness coefficient) and the increase of normal stress, to some degree, can weaken the effect of the shear direction. The joint failure process has remarkable stage characteristics. Under low and medium normal stress conditions, the shear resistance is mainly attributed to the climbing slip and friction slip, while under the high normal stress condition, it is owed to the mutual gnawing of bulges. The parameter of average inclination deviation is adopted to describe the shear anisotropy and an improved Barton model considering shear direction is proposed to better predict the joint shear strengths of positive and negative directions. With the percentile parameter, the relationship between the three-dimensional morphology indexes and the two-dimensional high-difference indexes is established to simplify the difficulties in obtaining the morphology index of the rock joints. With less calculating parameters and clear physical significance, the improved model has significant potential application value, for it can easily obtain data and take shear anisotropy of rock joints into consideration.