加筋土拉拔界面作用的离散元细观模拟

Discrete element mesoscopic simulation of the reinforced soil pullout test interface effect

为研究加筋土界面作用的力学响应,对离散元程序(PFC3D)进行二次开发,建立了土工格栅拉拔试验仿真模型。与室内模型试验结果进行对比,探讨了拉拔界面细观参数的演变及荷载传递机理,揭示了细观参数的演化规律及其与宏观力学性质之间的关系。研究结果表明:筋土界面区域成为主要的位移集中区,上界面影响厚度略大于下界面影响厚度;在筋土界面区域形成了高度的X向应力集中,沿格栅长度方向出现若干个Z向应力集中区,表明格栅横肋挤压土体,其所提供的被动承载力较为显著;在筋土界面区域,局部孔隙率随拉拔位移增大而增大,接触数减少,滑动比随拉拔位移的增加发生了激烈的跌宕起伏,界面局部位置发生剪胀,宏观上对应拉拔阻力增大,而后孔隙率慢慢减小,拉拔阻力回落。

Through the secondary development of discrete element method particle flow code 3 dimensions （ PFC3D） , the geosynthetics pullout test 3D numerical simulation model was established for researching the me-chanical response of the reinforced soil interface effect. The evolution of the mesoscopic parameters and load-trans-mitting of the reinforced soil interface region were studied through comparing the macroscopic mechanical properties with the laboratory model test results. The results show that the reinforced soil interface region has become the main displacement concentration area, and the upper interface thickness is slightly larger than the lower interface thick-ness. The stress concentration zones of the X direction in the reinforced soil interface region took shape, and several stress concentration zones in the Z direction appeared along the geogrid length direction, which demonstrates that the geogrid transverse ribs have extruded soil, and passive resistance of the transverse rib is significant. In the rein-forced soil interface region, with the pullout displacement increasing, the local porosity increases and the coordina-tion number decreases, the sliding fraction undergoes significant ups and downs, and the local location of the inter-face appears with shear dilatancy. The corresponding pullout resistance increases, then the porosity slowly decreases and the pullout resistance falls back in the macroscopic view.