重载货车作用下基床表层应力状态及破坏影响因素分析

Analysis of Subgrade Stress State and Factors Contributing to Subgrade Damage From Heavy Haul Freight Cars

重载货车作用下线路破坏问题与基床表层应力状态密切相关。通过建立货车-线路动力分析模型,分析货车通过时基床表层应力状态变化规律,研究道床厚度、轴重、速度、基床表层模量等因素对基床表层破坏的影响规律。结果表明:基床表层在车辆作用下遵循从纯剪到三轴剪切再回到纯剪状态的变化规律,主应力轴连续旋转180°;道床厚度低于0.5m、速度超过70km/h、基床表层模量低于160 MPa、轴重超过27t都有可能造成基床表层塑性变形;当应力路径超过破坏线情况下,路基弹性假设将不再适用。

The damage of railway lines during heavy haul freight train passage is closely related to the stress state of the subgrade surface.In order to study the stress path in subgrade soils under moving trains,this study utilized a dynamic freight-railway model to analyze such stress on during freight train operations.The study investigated the effects of ballast layer thickness,axle load,speed,and other factors contributing to subgrade surface damage.The extent of subgrade stress and related damage were obtained using the Euler beam model to analyze the elastic half-space under one moving load.The stress path in soils under the moving load was analyzed.Based on the modeling,it was determined that the stress state changes from pure shear to triaxial shear and back to pure shear in one cycle.According to the stress path curves for different moving speeds,it was determined that,when the moving load is high,the horizontal shear stress increases dramatically.The results further indicate that the stress state changes from the initial state to pure shear,to triaxial shear,and back to pure shear.The principle axis of stress rotates 180°.However,it is more complex due to the interaction of the wheels.A ballast layer deeper than 0.5m,train speeds exceeding 70km/h,the modulus of the subgrade materials less than 160 MPa,and an axle load higher than 27 t,all of these factors may result in the plastic deformation within the subgrade surface.If the stress path reaches the failure line,the hypothesis of elasticity will be invalid.