Research On The Influence Of Contact Loss Underneath Support Layer Of CRTSⅡ Slab Ballastless Track In High Speed Railway

CRTS Ⅱ slab ballastless track was firstly used in Beijing-Tianjin intercity passenger dedicated line.Due to the lack of experience in design,construction and maintenance,a series of different degrees of damage or injuries of the CRTS Ⅱ slab ballastless track gradually appear during the operation.At present,research on the damage of track slab is copious,but research on the damage of support layer underneath track slab is rare at home and abroad.It is significant to study the damage mechanism and influence of the support layer,as the support layer is an important structural component between the CRTS Ⅱ track slab and the subgrade structure.This thesis mainly studied the the damage mechanism and effect of contact loss underneath support layer.According to the field investigation data,the support layer contact loss is simplified into two forms,contact loss appears in slab end and slab edge.By means of finite element software-ABAQUS,vehicle-slab ballastless track-subgrade coupling dynamic models are established in this thesis to analyze,the influence of stress and deformation characteristics of the track and subgrade structure caused by different contact loss length under different contact loss conditions including contact loss in slab end and slab edge under train load;the influence of stress and deformation characteristics of the track and subgrade structure by different train speed and conditions of support layer contact loss.According to the relationship between the void length and the dynamic characteristics of the track and subgrade system,the following conclusions can be obtained:the adverse effects of the support layer diseases on the track and subgrade structure increase with the void length.When contact loss appears in slab ends in subgrade filled with soil,the cavity length of 1.95m should arouse attention,the lateral stress and deformation distribution of each layer of the subgrade is the same,but the lateral stress and deformation is larger than that of the former;When contact loss appears in slab edge,the cavity length of 0.975m should arouse attention,the stress and deformation of the edge of the slab is larger than that without the void,and the lateral stress and deformation distribution of each layer of the subgrade is the same.Based on the dynamic characteristics of track and subgrade structure under the condition of different vehicle speed and two kinds of support layer diseases,the dynamic responses of track and subgrade increase,which is harmful to the stability of track structure and driving safety.Combined with the selected dynamic response limit value to ensure the comfort of the train and the strength and durability of track system,the limit values of train speed corresponding to two kinds of support layer diseases are obtained respectively.