热力学方法在土体动力Ramberg-Osgood模型中的应用研究

Study of Application of Thermodynamic Methods to Dynamic Ramberg-Osgood of Soils

从Ramberg-Osgood模型的骨架曲线和滞回曲线出发,假定塑性中心的移动为直线,构造土体动力耗散函数,从热力学基本定律出发研究了土体动力耗散特性及动力变形机理.提出了反映筑坝堆石料动力特性的第1阈值应变和第2阈值应变,两个阈值应变主要受最大动剪切模量系数、指数及无黏性土的内摩擦角的影响.第1和第2阈值应变间屈服面的摩擦系数研究表明,当应力点沿滞回圈运动时,不同点的耗能机制随动应变水平的增大而差别变大;屈服面首先在摩擦系数小时发生弯曲,土体动力过程中发生间歇剪缩;当动应变继续增大,剪缩与剪胀同时发生.

Starting from the skeleton curves and hysteresis loop of Ramberg Osgood model, dynam- ic dissipation function is constructed, based on the assumption that the movement of plastic center fol- lows a straight line. The yield surface and energy dissipation mechanisms of dam materials at different dynamic strain amplitudes are discussed. Two types of cyclic threshold shear strain, i. e. , the first threshold shear strain and the second thresh old shear strain, are proposed to describe the dy namic characteristics of rockfill non-cohesive mate rials. The two threshold shear strains depend sig nificantly on the maximum dynamic shear modulus coefficient, exponent and internal friction angle of cohesionless soil. The study of friction coefficient of the yield surfaces between the first threshold strain and the second threshold strain indicates that when the stress points moving along the hys teresis loop, the difference between the energy dis sipative mechanisms becomes larger with the increasing dynamic strain amplitude. The yield surface first appears bending at small friction coeffi cient, and shear shrinkage will occur intermittently. When dynamic shear strain continues to in crease, shear shrinkage and dilatancy will occur simuhaneous[y.