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Investigations of granular specimen size effect in interface shear box test using a micro-polar continuum description
International Journal for Numerical and Analytical Methods in Geomechanics ( IF 4 ) Pub Date : 2021-09-21 , DOI: 10.1002/nag.3273
Erich Bauer 1 , Babak Ebrahimian 2
Affiliation  

Parametric studies were carried out to investigate the effects of specimen size and interface friction angle on the mechanical behaviour of a cohesionless granular material in the interface shear box test under constant normal load and plane strain conditions. For a description of the pressure and density dependent properties of granular materials such as sand, a micro-polar hypoplastic continuum model is used. Numerical simulations were performed to obtain the evolution of the deformations and the shear resistance for three different specimen lengths and interface friction angles using the finite element method in the updated Lagrange frame. Due to the presence of lateral rigid boundaries of the shear box, the deformations and the stresses became significantly inhomogeneous within the granular specimen. Correspondingly, the mobilised interface shear resistance and the deformation field within the specimen were not uniform along the interface. In the case of higher interface friction angles, the evolution of the mechanical quantities along the interface can also be influenced by the specimen size. It is shown that the calculated average friction angle mobilised along a rough interface is influenced by the shear box length and it can be lower than the prescribed one. In addition, the influence of sidewall friction inside the shear box frame was explored in terms of the response of the specimen. The results of the micro-polar hypoplastic model were also compared with those obtained from the corresponding non-polar version of the model to clarify the role of polar effects within the granular body. The numerical results provide new insights into the microstructural effects of the granular material on the mobilisation of the interface friction angle and indicate the complexities and difficulties to precisely determine and interpret the interface friction angle, obtained from the classical interface shear box experiment.

中文翻译:

基于微极连续谱描述的界面剪切箱试验中颗粒试样尺寸效应的研究

进行了参数研究,以研究试样尺寸和界面摩擦角对在恒定法向载荷和平面应变条件下的界面剪切盒试验中无内聚颗粒材料力学行为的影响。为了描述粒状材料(例如沙子)的压力和密度相关特性,使用了微极低塑性连续体模型。使用有限元方法在更新的拉格朗日框架中进行数值模拟以获得三种不同试样长度和界面摩擦角的变形和剪切阻力的演变。由于剪切箱的横向刚性边界的存在,颗粒试样内的变形和应力变得明显不均匀。相应地,试样内部的流动界面剪切阻力和变形场沿界面不均匀。在较高的界面摩擦角的情况下,沿界面的机械量的演变也会受到试样尺寸的影响。结果表明,计算出的沿粗糙界面移动的平均摩擦角受剪切箱长度的影响,可能低于规定值。此外,根据试样的响应,探讨了剪切箱框架内侧壁摩擦的影响。还将微极性发育不良模型的结果与从模型的相应非极性版本获得的结果进行比较,以阐明极性效应在颗粒体内的作用。
更新日期:2021-11-12
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