循环荷载下土工格栅加筋铁路道床累积#br# 沉降模型试验研究

散粒体道床层的循环累积变形是有砟轨道沉降的主要来源，文章采用有砟轨道路基模型试验来研究道砟层与底砟层间布置土工格栅加固道床控制有砟轨道沉降，开展了高速和重载等不同列车荷载下与不同类型土工格栅加固条件下的多组循环加载试验，加载过程中全程监测道砟层累积沉降、轨枕振动、道砟层底部土压力与土工格栅应变数据并进行分析，以研究土工格栅控制有砟轨道道床沉降的作用机理。研究结果表明：土工格栅对于控制道砟层累积沉降具有较显著的效果，但当土工格栅的刚度达到一定程度后刚度对土工格栅控制沉降效果的影响不大；土工格栅能够显著减小轨枕下方道砟层土压力峰值，从而降低道砟磨耗破碎程度及由此引起的道床沉降；道砟层累积沉降的发展意味着道砟颗粒的错动，而道砟颗粒的错动与位移将引起嵌锁于道砟层中的土工格栅发生张拉，从而土工格栅将反过来对道砟颗粒的进一步位移错动形成侧向约束，体现于宏观即表现为道砟层累积沉降得到控制。

Experimental study on accumulated settlement of ballasted trackbed #br# reinforced with geogrid under cyclic loading

The Accumulated deformation of ballast layer is the main source of the ballasted track settlement. Based on the model tests of ballasted track under high speed and heavy haul train load with different types of geogrid, the reinforcement of geogrid at the ballast-subballast interface were researched. The settlement of ballast layer, the vibration of sleeper, the vertical stresses at ballast-subballast interface and the strains of geogrids are detected to analyze the influence and mechanism of geogrid on ballasted track. It was found that the use of geogrid has a significant impact on reducing the settlement of ballast layer and the increase of the stiffness of geogrid has little influence on the reinforcement when that stiffness reaches a certain extent. For the stresses in the track, the geogrid also helps in reducing the peak value of vertical stress, thus relieving ballast particle breakage and reducing the relevant settlement of ballast layer. Moreover, it can be concluded that the movement of ballast particles can lead to the tension of geogrid interlocked with ballast particles, then the reaction of geogrid can give lateral confinement to control the further movement of ballast particles, which is shown as the control of accumulated settlement in macroscopic view.