Experimental Study On Dynamic Characteristics Of Contact Layer Between Ballast Bed And Subgrade Considering Intermittent Action Of Train Load

The increase of train axle load and marshalling will increase the action depth and times of train load on ballasted track subgrade.In addition,the ballasted track subgrade is exposed to the natural environment for a long time,which is easy to cause diseases such as mud boiling and hardening of track bed.Based on this,this thesis takes the contact layer between ballast track bed and subgrade as the research object,and carries out the experimental research on the dynamic characteristics and interaction phenomenon of the contact layer considering the intermittent action of train load.The main research work is as follows:(1)Carry out a series of indoor dynamic triaxial tests on the contact layer between ballast track bed and subgrade.The effects of water content,dynamic stress level and train formation on the interaction phenomenon and characterization index of contact layer are analyzed,and the empirical formula of the variation of characterization index with dynamic stress is established.The variation law of moisture content of Subgrade under different dynamic stress and compactness is analyzed,and the dirt degree of track bed is described and classified by using the dirt evaluation index VCI.(2)The results show that the existence of intermittent period enhances the ability of the sample to resist deformation and failure,and improves the dynamic stability of the sample;When the moisture content of the subgrade is saturated,the increase of train formation will aggravate the embedding degree of ballast particles and increase the overall deformation of the sample.The empirical formula of critical dynamic stress and cumulative plastic strain prediction model of contact layer are established.The stability failure criterion of cumulative deformation of contact layer is proposed.(3)Considering that the elastic modulus of the sample under intermittent train load shows three development forms: hardening type,hardening stable type and hardening softening type,and there is a good power function correlation with the cumulative plastic strain,the power function relationship between the cumulative plastic strain and the elastic modulus is established.The effects of dynamic stress and moisture content on the development law of damping ratio are analyzed.The damping ratio and elastic modulus are normalized,and the normalized characteristic model of damping ratio and elastic modulus is established.There are 70 figures,14 tables and 138 references.