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通过直剪条件下的模型试验研究具有相同连通率、含不同起伏角的共面闭合节理在不同法向应力作用下的剪切变形特征。试验结果表明:在达到峰值剪切强度前,剪切应力-位移曲线具有明显的线性段与非线性段;岩桥在法向与剪切荷载的共同作用下会产生一定程度的弱化,积累到一定程度时宏观表现为剪切应力软化。详细阐述了试验过程中裂纹发展的4个阶段并描述了剪切应力-剪切变形曲线变化的特征,提出一个能反映剪切应力-剪切变形曲线全过程的经验本构模型。新模型采用分段函数描述曲线变化特征。直剪试验数据分析表明,该模型能够拟合剪切应力-剪切变形变化发展趋势且具有较高的拟合精度,验证了模型的正确性。最后,对其存在的不足亦进行了简要分析。
Through the model test under direct shear conditions, the shear deformation characteristics of coplanar closed joints with the same connectivity rate and different relief angles under different normal stresses are studied. The experimental results show that the shear stress-displacement curve has obvious linear and nonlinear sections before the peak shear strength is reached. The rock bridge weakens to a certain extent under the combined effect of normal and shear loads A certain degree of macroscopic shear stress softening. The four stages of crack development during the test are described in detail, and the characteristics of shear stress-shear deformation curve are described. An empirical constitutive model that reflects the whole process of shear stress-shear deformation curve is proposed. The new model uses piecewise function to describe the characteristics of curve changes. The analysis of direct shear test data shows that the model can fit the development trend of shear stress-shear deformation and has high fitting accuracy, which verifies the correctness of the model. Finally, the shortcomings of its existence are also briefly analyzed.