砂土流变行为的热力学本构模型研究

Thermodynamic constitutive model for rheological behavior of sand

采用非平衡态热力学方法,通过引入颗粒熵sg和颗粒温度Tg描述砂土颗粒间碰撞、滑动、滚动等相互作用,用颗粒温度引起的弹性弛豫反映砂土内部的不可逆变形,构建了描述砂土宏观力学行为的热力学方程组。通过合理简化该热力学方程组分析了侧限压缩试验和各向同性压缩试验的流变规律,分析表明:简化的热力学模型能够较好地反映和预测砂土蠕变和松弛行为;砂土在外力加载过程中,颗粒熵(颗粒温度)被激发不断增大直至稳定值,在停止加载后的流变过程中,颗粒熵(颗粒温度)逐渐衰减,理论上最终衰减为零(排除外界扰动);颗粒熵衰减过程中,颗粒温度引发的弹性弛豫宏观表现为流变行为,随着颗粒熵衰减为零,理论上流变最终停止在一个稳定值。

Based on the non-equilibrium thermodynamics, a granular entropy sg and a granular temperature Tg are introduced to describe the collisions, sliding, rolling of sand particles. The elastic relaxation caused by granular temperature variation is used to reflect the irreversible deformation of sand. The thermodynamic governing equations are derived to predict the macroscopic mechanical behavior of sand. Confined compression and isotropic compression tests are investigated using the proposed method. The results indicate that the proposed model can well describe sand relaxation and creep behavior. The granular entropy is excited and increases until a steady value in loading process, and the granular entropy gradually decays until to zero in the rheological process after loading. The elastic relaxation caused by granular temperature leads to the rheological behavior, and the rheology eventually stops at a steady value when the granular entropy decays to zero.