重载货车作用下基床表层应力状态及破坏影响因素分析①

时瑾， 杨雪

(北京交通大学土木建筑工程学院，北京 100044)

摘要：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0.5 m、速度超过70 km/h、基床表层模量低于160 MPa、轴重超过27 t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。

关键词：重载铁路； 基床表层； 动力响应； 应力状态

收稿日期：①2014-08-20

基金项目：北京高等学校青年英才计划项目(YETP0560)；上海市科技人才计划项目(13XD1401800)

作者简介：时瑾(1980-)，男，副教授，研究方向为轨道交通线路系统动力学。E-mail:jshi@bjtu.edu.cn。

中图分类号:U213文献标志码：A

DOI:10.3969/j.issn.1000-0844.2015.03.0851

AnalysisofSubgradeStressStateandFactorsContributingto

SubgradeDamageFromHeavyHaulFreightCars

SHIJin，YANGXue

(School of Civil Engineering，Beijing Jiaotong University，Beijing 100044，China)

Abstract：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 0.5 m，train speeds exceeding 70 km/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.

Keywords：heavy-haulrailway；subgradesurface；dynamicresponse；stressstate

0引言

近年来我国重载运输取得了快速发展，目前既有重载线路已普遍开行25t轴重万吨列车，27t、30t大轴重列车也已上线运行。随着重载列车轴重、密度的提高，列车对线路的动力影响愈加显著，线路运营条件也愈加恶化。基床表层直接承受道床传来的动载，是运营过程中产生病害的薄弱环节。随着轮轴移动，基床动应力重复变化，应力状态与线路破坏密切相关，开展重载货车作用下基床表层应力变化规律，可为有针对性地拟定加强措施提供科学指导。……