刚性与柔性顶部边界下筋土界面特性的细观数值研究

Mesoscopic numerical studies on geogrid-soil interface behavior under rigid and flexible top boundary conditions

土工格栅拉拔试验被认为是研究土工格栅与土相互作用行为最直接有效的方法。在土工格栅拉拔试验中,常采用刚性或柔性顶部边界条件施加竖向荷载。为了研究刚性与柔性顶部边界条件对拉拔试验结果的影响,基于离散元数值模拟,从细观层面深入分析了刚性与柔性顶部边界条件下土工格栅与土的力学响应。研究结果表明:在拉拔位移较小的情况下,刚性与柔性顶部边界条件对拉拔试验结果几乎没有影响;随着拉拔位移的增大,顶部边界条件对拉拔试验结果的影响逐渐明显,刚性顶部边界条件下的最大拉拔阻力略大于柔性顶部边界条件下的最大拉拔阻力;土工格栅张力与试样内部土颗粒间接触力分布情况、试样内部土颗粒旋转情况以及顶部加载板颗粒的竖向位移分布规律直观地展现了顶部边界条件对拉拔试验结果的影响。本研究结果有望为规范土工格栅拉拔试验方法提供科学依据。

The pullout tests on geogrids have been regarded as the most direct way to investigate the geogrid-soil interaction.In the pullout tests on geogrids,either a rigid or a flexible top boundary is commonly used for applying the vertical loads.In order to investigates the influence of rigid and flexible top boundaries on pullout test results,discrete element modeling is carried out to deeply analyze the mechanical response of geogrids and soils under rigid and flexible top boundary conditions from the mesoscopic scale.The results show that the rigid and flexible top boundaries have almost no effects on the pullout test results when the pullout displacement is small.With the increasing pullout displacement,the influences of the top boundaries on the pullout test results become obvious.The maximum pullout resistance under the rigid top boundary conditions is slightly larger than that under flexible ones.Moreover,the influences of the top boundaries on the pullout test results can be visualized by the tensile force distribution of geogrids,the contact force distribution of soil particles in the specimens,the rotations of soil particles and the vertical displacement distribution of top loading particles.The investigation results in this study may provide scientific references for regulating the pullout test methods for geogrids.