Research On Deformation Characteristics Of Silty Filler For Heavy-Haul Railway Subgrade Considering Loading Intermittence And Overlying Ballast Action

Railways are the national key infrastructures,main artery of the national economy and the major livelihood projects.As the substructure of railways,the subgrade is the foundation of the entire railway transportation.The deformation characteristics of the subgrade filler directly determine the dynamic stability of the subgrade under the dynamic loading of the large-axle heavy-haul trains,and play a key role in ensuring the safety of the line.Relying on the National Natural Science Foundation of China and Shenhua Science and Technology Innovation Project,a series of static/dynamic triaxial tests have been carried out to systematically study the deformation characteristics of silty fillers for the heavy-haul railway subgrade.The main work and results are as follows:1)A series of continuous loading and intermittent loading dynamic triaxial tests,considering that the train dynamic loading on the subgrade is an intermittent cyclic loading,have been carried out with the ShuozhouHuanghua heavy-haul railway subgrade silty filler as the research object.By comparing the excess pore water pressure,elastic strain,elastic modulus and cumulative plastic strain of the silty filler under the two loading modes,the effects of the loading intermittence and the duration of the loading intermittence on the deformation characteristics of the subgrade silty filler have been clarified.2)According to shakedown theory,the deformation behaviors of silty filler under intermittent loading can be divided into plastic shakedown,plastic creep and incremental collapse.In view of the deficiency of the shakedown theory in the indicators and standards for the division of deformation behaviors,the shakedown theory has been revised.Based on the plastic strain rate and the elastic strain,the classification standards of deformation behaviors for intermittent loading have been established.Furthermore,a model for predicting the critical dynamic stress level of silty filler has been proposed,which can also consider the influence of moisture content.3)Based on the influence of loading intermittence on the deformation characteristics of silty filler,the prediction models for cumulative plastic strain,resilience modulus and backbone curves have been established,in which the effect of loading intermittence can be reflected.4)Taking the gravel track bed-silty subgrade structure of ShuozhouHuanghua heavy-haul railway as the background,a double-layer sample with ballast gravel on the upper layer and silty filler on the lower layer has been designed,and a series of intermittent dynamic loading triaxial tests under different dynamic stress levels and moisture contents have been carried out.Indexes for quantitatively characterizing the degree of ballast penetration have been first proposed,then the elastic deformation,cumulative plastic deformation and lateral deformation of the ballast-silt sample as a whole have been analyzed,and the failure modes and standards of the ballast-silt sample have been discussed.This research provides a reference for understanding the deformation characteristics and evaluating the working performances of the heavy-haul railway subgrade under the action of actual train dynamic loading,and also provides technical support for exploring the working potential of the existing heavy-haul railway subgrade.