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切向荷载作用下贯通节理岩体峰值强度后的剪切应力、位移变形规律一般呈双曲线形式发展,即峰值后强度衰减速率逐步变小而趋于0,到达残余强度。直剪试验表明,非贯通节理岩体峰值后剪切应力、位移呈“S”型趋势发展,即强度衰减速率先是逐步增大,到达一定程度后逐步减少,最后趋于稳定达到残余强度值。贯通节理岩体峰值强度后的本构关系并不适合于描述该特征。提出一个新的非线性归一化位移软化本构模型,通过归一化剪切应力R与归一化剪切位移D的指数函数关系体现峰值后剪切应力、位移的发展趋势,即模型采用无量纲表达式。归一化剪切应力R是峰值后强度降τp-τ与峰值强度、残余强度差值τp-τr的比值;归一化位移D是峰值后剪切位移、峰值位移差值δ-δp与残余位移、峰值位移差值δr-δp的比值。对含不同起伏角的非贯通节理岩体在常法向荷载条件下的直剪试验数据进行拟合分析,模型预测结果与实测值具有相当高的吻合度,验证了模型的正确性。
The shear stress and displacement deformation under the tangential load after the peak strength of the jointed rock mass generally develop in the form of hyperbolic curve, that is, the intensity decay rate decreases gradually towards 0 and reaches the residual strength after the peak load. The direct shear test shows that the shear stress and displacement of non-through-jointed rock mass are in the trend of “S ” type, that is to say, the intensity decay rate firstly increases gradually and reaches a certain level and then decreases gradually, finally reaches the stable residual strength value. The constitutive relation after penetrating the rock mass peak strength is not suitable for describing this feature. A new nonlinear normalized displacement-softening constitutive model is proposed. The exponential function of normalized shear stress R and normalized shear displacement D shows the development trend of post-peak shear stress and displacement. That is to say, Dimensionless expression. The normalized shear stress R is the ratio of the post-peak intensity decrease τp-τ to the peak intensity and the residual intensity difference τp-τr. The normalized displacement D is the post-peak shear displacement, the peak displacement difference δ-δp and the residual Displacement, peak displacement difference δr-δp ratio. The direct shear test data of non - through jointed rock masses with different undulations are fitted and analyzed under the normal normal load. The results of the model prediction are in good agreement with the measured values, which proves the correctness of the model.