| CRTS Ⅱ slab track is one of the most applied ballastless track types in domestic highspeed railways and subjected to the temperature load for a long time in practice.Track slabs are easy to upwarp at a high temperature,which has a certain influence on high-speed driving.This thesis systematically analyzes the inducement and control measures of the hightemperature upwarp of CRTS Ⅱ slab track by combining theoretical derivation and numerical simulation.The main research contents are as follows:(1)An analytical formula for the upwarp of CRTS Ⅱ slab track is derived.Taking the stress state when CRTS Ⅱ track slab upwarp as a starting point,a corresponding mechanical model for upwarp is proposed based on reasonable assumptions.The energy variational method is used to derive the theoretical formula for the upwarp stability of track slabs,and the calculation results are compared with those in relevant references.The results show that: When the same conditions are applied,the calculation results of the critical temperature rise for the upwarp of track slabs by the equal wavelength model and unequal wavelength model are both closer to the practical circumstance.The variation laws of the upwarp balance path of track slabs calculated by the above two models are basically consistent.Similarly,the variation laws of the upwarp range and wavelength calculated by the two models are also basically consistent.It is suggested that the unequal wavelength model be applied in the calculation.(2)The influence of different construction stages on initial track damage is analyzed.According to the construction sequence and characteristics of track structures,a CRTS Ⅱ slab track model is established to simulate the two construction stages that are divided into one before longitudinal connection and the other after it.The influence of the damage,caused by the overall temperature rise load,temperature gradient load and longitudinal tension,between the layers of track structures and between the track slabs is analyzed.The results show: The initial damage to track structures occurs in the construction stage,and the overall temperature rise is the main reason.It is suggested that the overall temperature rise of track structures in the construction stage should be less than 10℃ when the strength of the concrete at narrow joints is considered as the evaluation index.(3)The influence of different damage states of narrow joints on the upwarp stability of track slabs is studied.Given the characteristics of track structures in the operation stage and the narrow joint defects that frequently occur on site between the track slabs,CRTS Ⅱ slab track models under different damage states of narrow joints are established.The influence of different defect heights,defect width and concrete quality on the upwarp stability of track slabs is studied.The results show: When there exist narrow joint defects,the defect guiding effect would obviously reduce the upwarp stability of track slabs;The height defect of narrow joints has the most significant effect on the upwarp of track slabs.When the temperature rise is 55℃ and the defect height of a narrow joint is 70 mm,the upwarp range of the track slab is close to 2 mm.Attention should be paid when a narrow joint defect exceeds 70 mm. |
