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各向异性对砂土强度和变形特性有显著的影响,为了研究各向异性砂土的宏微观特性,基于三维离散元法,对七个不同沉积角的试样进行了一系列的三轴模拟试验。利用“Clump”命令生成近似椭球形状颗粒,并且采用三维抗转动模型来模拟颗粒间的抗转动能力。离散元模拟结果与已知室内试验结果吻合很好。结果表明:随着沉积角的增大,偏应力和轴向应变的关系逐渐由应变软化向应变硬化发展。沉积角较小的试样剪胀性更强并且容易到达临界状态,颗粒组构-应力联合不变量(表征颗粒长轴组构张量和应力张量的相对角度)的值接近于-1,且颗粒长轴组构各向异性先增大后减小;然而对于沉积角较大的试样,在轴向应变50%处,仍不能达到临界状态,并且联合不变量的值大于-1,颗粒长轴组构各向异性先减小后不断增大。对于法向接触组构,组构主轴方向迅速向应力主轴方向偏转,组构各向异性的演化规律与偏应力随轴向应变的演化规律相似。
Anisotropy has a significant impact on the strength and deformation characteristics of sand. To study the macro-microscopic characteristics of anisotropic sand, a series of three-axis simulations were performed on seven samples with different deposition angles based on three-dimensional discrete element method test. The “Clump” command is used to generate approximate ellipsoid-shaped particles, and a three-dimensional anti-rotation model is used to simulate the anti-rotation ability of the particles. Discrete element simulation results agree well with the known indoor test results. The results show that as the deposition angle increases, the relationship between deviatoric stress and axial strain gradually develops from strain softening to strain hardening. The samples with smaller deposition angle have stronger dilatancy and are easy to reach the critical state. The value of the particle structure-stress joint invariant (the relative angle representing the long axis tensor and stress tensor) is close to -1, And the anisotropy of the long axis of the particles first increases and then decreases. However, for the sample with larger deposition angle, the critical state can not reach 50% of the axial strain, and the value of the joint invariant is greater than -1, The anisotropy of the long axis of the particles first decreases and then increases. For the normal contact structure, the direction of the principal axis of the composition is rapidly deflected to the direction of the principal stress axis. The evolution of anisotropy and the evolution of deviatoric stress with axial strain are similar.