等幅剪应变下砂土循环单剪行为的离散元模拟

发布时间：2018-07-31 15:19

【摘要】：循环动载下土体变形呈现的复杂各向异性,本质上依赖于土体微观组构特征的演化。为了揭示非比例循环动载下土体变形的微观机制,采用离散元方法模拟砂土的循环单剪行为。应用等幅剪应变的往复加载实现循环单剪应力路径,模拟得到了砂土的循环弱化、剪胀性、非共轴性及微观组构的演化规律。微观模拟表明,在循环剪切过程,土体表现为循环弱化行为,并最终趋于塑性安定状态。而试样组构主方向倾角和组构各向异性系数也会不断增大直至一个稳定值,同时主应变率、主应力轴和组构主方向旋转角度会存在一定的差异,即非共轴现象,随着单调剪切的进行,三者会逐渐趋于一致。土体的剪胀行为表现为循环压密性,而非共轴性呈现逐渐增强的演化规律。循环剪切过程中微观组构的主方向与应力主方向逐渐趋于一致,而微观组构各向异性呈现减弱的演化趋势。
[Abstract]:The complex anisotropy of soil deformation under cyclic dynamic load essentially depends on the evolution of soil microscopic fabric characteristics. In order to reveal the microscopic mechanism of soil deformation under non-proportional cyclic dynamic loading, the discrete element method is used to simulate the cyclic shear behavior of sand. Cyclic single shear stress path is realized by reciprocating loading of constant amplitude shear strain. The evolution laws of cyclic weakening shear expansion non-coaxial and microscopic fabric of sand are obtained by simulation. The microscopic simulation shows that the soil exhibits cyclic weakening behavior and tends to plastic stability during cyclic shear process. And the inclination angle and anisotropy coefficient of the fabric direction will increase until a stable value, and the principal strain rate, the rotation angle of the principal stress axis and the principal direction of the fabric will be different, that is, the non-coaxial phenomenon. With the monotone shear, the three will gradually converge. The shear expansion behavior of soil is cyclic compaction, but the non-coaxial behavior is gradually enhanced. In the cyclic shear process, the principal direction of microscopic fabric and the principal direction of stress tend to be consistent, while the anisotropy of microscopic fabric shows a tendency of weakening.
【作者单位】：同济大学地下建筑与工程系;同济大学岩土及地下工程教育部重点实验室;
【基金】：国家自然科学基金(No.41272291,No.51238009,No.51578413)~~
【分类号】：TU441

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