运梁车荷载作用下粗粒土填料的回弹与累积塑性应变特性研究

Research on the resilience behaviour and accumulated plastic strain characteristics of coarse-grained soil under transporting girder vehicle loading

高速铁路建设期间运梁车动荷载与运营期间高铁列车动荷载有很大区别,运梁车作用下产生的动应力远大于高铁列车作用下产生的动应力,易导致新建高铁路基表面平整度变差,沉陷明显。为探讨路基填料在大型运梁车动荷载作用下的动力特性,选取典型高铁路基断面,进行现场实车测试,获得运梁车作用下路基的动应力。以路基基床粗粒土填料为研究对象,开展一系列考虑围压、动应力、含水率等因素的大型动三轴试验,分析围压、动应力及含水率对粗粒土填料变形特性的影响。结果表明,稳定试样的滞回曲线斜率随振次逐渐变大,且表现出变形积累性、滞后性和非线性。加载初期试样回弹模量迅速减小,波动较大,然后随着振次的增加逐渐稳定或有所增加;回弹模量值随围压和动应力的增大而增大,随含水率增加而减小。基于安定理论,非饱和试样塑性变形行为类型都为塑性安定,而饱和试样塑性变形行为类型在动应力较小时为塑性蠕变,动应力较大时为增量破坏;累积塑性应变随动应力和含水率的增大而增大,随围压的增大而减小,其中含水率影响最为显著,并基于试验结果建立了累积塑性应变预测模型。研究结果可为正确认识运梁车荷载作用下路基填料的变形行为提供依据。

Significant disparities exist between the dynamic loading induced during high-speed railway construction by girder trucks and those encountered during regular high-speed train operations.The dynamic stress caused by the transporting girder vehicle loading is much greater than that induced by the high-speed train,which easily leads to the deterioration of the surface smoothness of newly constructed high-speed railway subgrade surface.In order to investigate the dynamic characteristics of the subgrade under transporting girder vehicle loads,a typical high-speed railway subgrade section was subjected to field test,with the aim of obtain the dynamic stress of high-speed railway subgrade under transporting girder vehicle load.Then,a series of largescale dynamic triaxial tests were conducted and the deformation behavior of the coarse-grained filler was analyzed,taking into consideration key factors such as different moisture content,confining pressure,and dynamic stress level.The results indicate that the slope of the hysteresis curve of the stable specimen shows obvious deformation accumulation,hysteretic and non-linearity,tends to increase gradually with the increasing loading cycle.The resilient modulus of the specimen fluctuates greatly and decreases rapidly at the initial stage of loading,and then gradually stabilizes or increases with the increasing loading cycles.The resilient modulus increases with the increase of confining pressure and dynamic stress,while it decreases with the increase of moisture content.Based on the shakedown theory,the plastic deformation behavior of unsaturated specimens behaves plastic shakedown,while the plastic deformation behavior of saturated specimens is plastic creep when the dynamic stress is small,and incremental collapse when the dynamic stress is large.The accumulative plastic strain increases with the increase of dynamic stress and moisture content,and decreases with the increase of confining pressure.Among these factors,water content emerges as the most significant determinant.Based on the experimental findings,a predictive model for cumulative plastic strain is established.The research could provide an insight into understanding the deformation behavior of subgrade filler under transporting girder vehicle loading.