Research On Dynamic Strength And Deformation Characteristics Of Graded Crushed Stone Filling With Different Fine Content In Heavy Haul Railway

The railway subgrade,as an important structure to bear the static load of the track and the cyclic load of the train,is the key to ensuring the safe operation of the train.With the increase of the axle load of heavy haul trains,the cyclic load of trains on the subgrade also increases.Among them,the surface layer of subgrade bed is the area that bears the cyclic load of the train and the environmental impact in the subgrade structure.Therefore,higher requirements are imposed on the surface layer of subgrade bed filler.In this paper,the effect of fine content,confining pressure,and dynamic stress amplitude on dynamic strength and deformation characteristics of graded crushed stone filling in the surface layer of subgrade bed is studied by conducting large-scale dynamic triaxial tests,to provide a reference for the dynamic deformation stability evaluation and the design of subgrade based on dynamic deformation control of heavy haul railway subgrade.Based on the analysis of experimental data,the main research contents and results are as follows:(1)Through a large number of large-scale dynamic triaxial tests,the relationship curves between the cumulative axial strain of the sample and the number of vibrations under different confining pressures,different fine contents,and different dynamic stress amplitudes and the critical dynamic stress of graded crushed stone filling under different fine contents and different confining pressures test conditions were obtained.The influence of confining pressure and fine content on it was analyzed,and it was found that the critical dynamic stress increased with the increase of confining pressure and decreased with the increase of fine content.(2)The effects of fine content,confining pressure,and the number of damage vibrations on the dynamic strength and dynamic strength indexes c_d andφ_d of the sample under cyclic loading were studied.With the increase of the number of damage vibrations,the dynamic strength indexes c_d andφ_d of the graded crushed stone filling sample and the dynamic stress required for damage gradually decrease;With the increase of fine content,the dynamic cohesion c_d gradually increases,while the dynamic internal friction angleφ_d gradually decreases.(3)The effects of confining pressure and fine content on the dynamic deformation characteristics of the sample are analyzed.As the confining pressure increases,the cumulative strain development rate of the filler decreases,and the size of the confining pressure can also change the type of cumulative strain development of the sample.As the content of fine particles increases,the cumulative plastic strain in the axial direction gradually increases,while the rebound strain decreases.(4)The influence of confining pressure and fine particle content on the critical dynamic stress ratio is analyzed,and an empirical formula for the critical dynamic stress ratio considering the two factors of confining pressure and fine content is proposed.(5)Based on the dynamic performance of the test results,the applicability of graded crushed stones with different fine content in the filling of the surface layer of the subgrade bed is discussed.The filling of the surface layer of the heavy haul railway subgrade bed should use a graded crushed stone filler with a low fine content.