考虑转动阻抗作用的砂土模拟直剪试验

基于离散单元法进行一系列砂土直剪数值模拟试验，探究存在转动阻抗作用时颗粒抗转能力与砂土相互作用间宏细观力学的内在联系。通过抗转动线性接触模型模拟砂颗粒间的接触本构关系，得出的宏观应力-应变特性、强度指标和剪切带变形规律与前人研究相类似，验证了砂土直剪数值模拟试验的可行性。细观层面，试样内平均力学配位数及强接触比例均随着抗转动系数的增大而减小。结合玫瑰图、偏组构和第二不变量表征的张量研究各向异性的演化规律发现:在剪切过程中，法向接触力和切向接触力的各向异性均随抗转动系数的增大而增大，其中强接触偏组构均大于整体接触偏组构，法向接触力张量均大于组构张量且与宏观抗剪强度变化规律具有一致性，这表明转动阻抗主要通过增大颗粒间强接触力的数值及其组构的各向异性程度提高抗剪强度，法向接触力各向异性对抗剪强度具有关键作用。

Numerical simulation of direct shear test of sand considering rotational impedance

A series of sand direct shear numerical simulation tests were performed using the discrete element method, so as to investigate the inherent relation of meso-mechanics between the particle’s rotation-resistant capacity and the interaction of sands and soils in the case of rotational resistance. On this basis, the contact constitutive relation between sand particles was simulated with the rolling resistance linear model. Meanwhile, the feasibility of the sand direct shear numerical test was verified by numerically experimenting macro stress-strain characteristics, strength index and shear band deformation law that are similar to previous studies. In addition, from the meso scale, the average mechanical coordination number and the strong contact proportion in the sample decreased with the increase of the rolling resistance coefficient. After studying the anisotropic evolution law in combination with the tensors characterized by rose diagram, deviator fabric and second invariant, it is found that the anisotropy properties of the normal contact force and the tangential contact force are increased with the increase of the rolling resistance coefficient in the shearing process. The strong contact deviator fabric is greater than the overall contact deviator fabric. Besides, the tensors of normal contact forces are greater than those of fabrics, which has a variation law consistent with the macroscopic shear strength. It is evidently indicated that the rotational impedance principally improves the shear strength by increasing the magnitude of strong contact force between particles and the degree of anisotropy of the fabric. Also, the anisotropy of the normal contact force plays a pivotal role in resisting the shear strength.