重载铁路路基粗颗粒土循环振动试验与累积动应变研究

Cyclic Vibration Tests on Coarse Grained Soil of Heavy Haul Railway Subgrade and Study on Accumulative Dynamic Strain

重载铁路路基核心层为粗粒土,其直接承受轨道结构传递的列车动载的往复作用,但目前对粗粒土填料在重载列车往复作用下累积动应变的研究较少。为探索粗粒土填料在暴雨等极端恶劣天气或路基浸水时的累积动应变变化规律,利用基于MTS精确控制的动三轴试验系统,进行不同围压、多组动应力幅值下饱和粗颗粒土(铁路路基A级填料)的振动试验。由此获得一系列粗颗粒土累积动应变与振动次数的关系曲线,揭示动应力比对累积动应变发展类型的影响,得出基于围压的临界动应力比表达式以及累积动应变与振动次数的拟合关系式,同时证明一定振动次数时试样动应力与累积动应变关系比较符合双曲线模型。试验结果可供重载铁路路基核心层的动力变形稳定性评价和基于动力变形控制的路基设计参考和利用。

The core layer of heavy haul railway subgrade,which is directly subject to the cyclic loading from upper track structure,consists of coarse grained soil（CGS）.However,currently,fewer studies have been performed on accumulative dynamic strain（ADS）of CGS filler under the cyclic effect of heavy haul trains.In order to study the law of development of ADS of CGS filler under extreme weather conditions,such as heavy rain or under the situation when the subgrade suffers water immersion,an independently developed MTS-controlled triaxial testing system is used to carry out some dynamic triaxial tests of saturated CGS（railway subgrade class A packing）with different confining pressures and dynamic stress amplitudes.From these tests,the curve of the relationship between ADS and the number of vibration is acquired.Moreover,the effect of critical dynamic stress ratio（CDSR）on ADS developing type is discovered.The expression formula of CDSR based on confining pressure and the fitted formulas between ADS and the number of vibration are obtained.Finally,the results prove that the hyperbolic model could approximately fit the relationship between dynamic stress and ADS with certain number of vibration.The results of these tests could be utilized for reference for the evaluation of the dynamic stress deformation stability of the subgrade core layer of heavy haul railway and design of subgrade based on dynamic deformation control.