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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。
Joint shear strength related to rock engineering safety. Through the CSS-342 rock shear test machine, three groups of joints with different topographic features were subjected to direct shear test to study the effect of morphology on the shear strength. The experimental results show that the peak shear strength increases with the increase of normal stress and roughness, but in the same morphology, the ratio of shear stress to normal stress decreases, that is, the dilatancy angle Decreases with increasing normal stress. By analyzing the boundary conditions existing in dilatancy angle, a hyperbola dilatancy evolution model is proposed and the effect of rock properties on joint shear strength is expressed by tensile strength. The root mean square of slope is used to characterize the three-dimensional topography of the joint and the corresponding formula of peak shear strength is proposed. Compared with the classical Barton formula, the calculated value of the new formula is closer to the experimental value.