摘要：研究目的：为研究列车荷载下桩网结构路基中土拱效应的形成机理和受力特性，本文通过建立桩网结构 路基简化离散元模型，利用PFC3D软件对土拱效应机理进行细观研究，分析颗粒间的接触力链、颗粒的横向及 竖向位移以及路基中的颗粒应力竖向分布。研究结论：(1)动荷载作用后，桩间土应力增加，土拱效应被削弱；（2)动荷载作用下，路基中会形成动力 土拱，大部分动力会沿动力拱传递至桩顶上方;（3)等沉面的形成与位移拱有关，位移拱范围内桩顶上方颗粒挤人桩间土区域，从而导致位移拱范围外桩顶颗粒竖向位移增大，而桩间土颗粒竖向位移减小；（4)路基中设 置土工格栅会降低土拱高度，削弱应力拱内多个虚拟土拱的作用，但比土拱更能提高桩土应力比；（5)本研究 结果可为铁路路基结构工作机理分析提供思路和方法。

Abstract ： Research purposes ： To investigate the formation mechanism and mechanical characteristics of soil arching effect within pile net structure in embankment under train load，discrete element model of pile net structure is found by PFC3D software for mesoscopic research，the chain of contact force，the horizontal and vertical displacement，and vertical distribution of soil particles stress are analyzed in this paper. Research conclusions ：( 1) The soil stress between piles is increased and the soil arching effect is weakened by dynamic load. (2 ) Most of dynamic load is pased to the top of pile because of dynamic soil arching formation. ( 3 ) The formation of equal settlement surface is associated with the displacement arch，because the soil particles will run into the area between piles from the area on the top of piles within thedisplacement arch，which leads to a higher vertical displacement on the top of piles outside displacement arch and a lower soil vertical displacement between piles. (4) It will lower soil arch height and weaken virtual soil arches among stress arch if the geogrid cushion is put into use，but the pile - soil stress ratio is increased. ( 5 ) This research results will provide method of working mechanism for railway roadbed Ntructure.