土工格室与砂土拉拔试验离散元细观分析

Discrete element meso-analysis of pullout test of geocell and sand

为研究土工格室加筋砂土的界面作用特性,采用离散元程序(PFC3D)建立土工格室加筋砂土的拉拔试验数值模型,分析了拉拔过程中的筋土界面位移、格室节点受力及界面接触力和孔隙率等宏细观参数的变化规律,揭示了土工格室加筋砂土在拉拔过程中筋土界面作用的宏细观机理。结果表明:格室拉拔阻力主要由格室纵肋界面摩擦阻力及格室横肋的被动承载力组成,界面摩擦阻力在前期发挥主要作用,而横肋的被动承载力在后期发挥主要作用;筋土界面区域的土体接触力和局部孔隙率随拉拔位移发生疏密相间的变化,界面区域砂土发生脱空,同时局部土体产生剪胀作用,对应界面孔隙率增大;宏观上随着拉拔位移增加,颗粒挤密咬合能力增强,对应的细观参数(界面接触力和界面局部孔隙率)发生起伏变化,界面区域接触力增大从而使得拉拔阻力随格室拉拔位移的增大而增大。

In order to study the interfacial action characteristics of geogrid reinforced sand,the numerical model of the pullout test of the geocell reinforced sand is established by using the discrete element program (PFC3D).The reinforced interface displacement,the force of geocell node and the interface contact force and porosity are analyzed.And the macroscopic mechanism of the interface interaction of geocell reinforced sand during the pullout test process is revealed.The results show that the pullout resistance of geocell mainly consists of the interfacial friction resistance of the longitudinal ribs and the passive bearing capacity of the transverse ribs of geocell.The interface frictional resistance plays a major role in the early stage,while the passive bearing capacity of the transverse ribs plays a major role in the later period.Soil contact force and local porosity of reinforced soil interfacial region vary with the drawdisplacement.The sand in the interfacial region is devoid of space,and dilatancy occurs in the local soil,which corresponds to the increase of the interfacial porosity.With the increase of drawing displacement,the extrusion and occlusion ability of the particles is enhanced,and the corresponding meso parameters(interface contact force and interface local porosity) occur fluctuating,and the contact force in the interface area increases,which makes the pullout resistance increase with the increase of the pullout displacement.