基于三轴试验红层泥岩的邓肯-张模型参数研究

Duncan—Zhang Model Parameters of Red Mudstone Based on Triaxial Tests

兰州地区红层泥岩形成于干旱、半干旱环境,其物理力学特性与其他地区的红层泥岩不同。以G6京藏高速兰海养护维修工程的红层泥岩路基填料为研究对象,通过大量的常规三轴试验,研究含水率对其力学特性及邓肯-张模型参数的影响。结果表明:在不同含水率下兰州地区红层泥岩的应力-应变曲线关系符合双曲线模型。含水率小于最优含水率时,破坏形式为剪切破坏;含水率大于最优含水率,破坏形式为鼓状破坏;随着含水率的增加,黏聚力和内摩擦角逐渐减小,内摩擦角减小的幅度更大,究其原因是含水率对黏聚力和内摩擦角的影响机理不同而导致。采用数学模型进行拟合发现:黏聚力、内摩擦角与含水率分别呈二次抛物线与对数曲线关系。不同含水率下邓肯-张模型参数破坏比R_f在区间(0.869,0.984)内波动,K值随含水率增大而减小呈负线性关系,n值随含水率的增大而增大呈线性关系。

The red mudstone in the Lanzhou area formed in arid and semi-arid environments has different physical and mechanical properties than that in other areas.This study investigates the red mudstone roadbed filling of Lanzhou-Haikou Maintenance Project in G6 Beijing-Tibet Expressway.Through a large number of conventional triaxial tests,the influences of the water content on the mechanical properties and Duncan-Zhang model parameters of the red mudstone were studied.The results show that the stress-strain curve of the red mudstone in the Lanzhou area satisfies the hyperbolic model under different moisture contents.When the moisture content is less than the optimum content,the failure mode is shear failure;when the moisture content is greater than the optimal moisture content,the failure mode is drum failure.With the increase of water content,the internal friction angle gradually decreases more than cohesion because the water content has different effects on the cohesion and internal friction angle.The mathematical model was used for fitting,and it was determined that the relation between the cohesion and water content and the relation between the internal friction angle and water content featured a quadratic parabola and logarithmic curve,respectively.The failure ratio, R f ,of Duncan-Chang model parameters under different moisture contents fluctuates within the interval (0.869,0.984);the K value decreases linearly with the increase of water content,and the n value increases linearly with the increase of water content.