Experimental Research On The Mechanical Performance Of Ballastless Track Slabs And Optimization Of Two-layer Two-way Pre-tensioned Prestressing Ballastless Track Slabs

Lots of ballastless track slabs were used in High-Speed Rail (HSR) projects inChina nowadays. Investigations of ballastless track slabs on two railways were carriedout to get the detailed using information. CRTS I and CRTS II as well as two-layertwo-way pre-tensioned prestressing ballastless track slabs were tested and simulated infinite-element analysis to investigate the mechanical behavior. Mechanical behaviorof two-layer two-way pre-tensioned prestressing ballastless track slabs under the affectof temperature was analysed and its influencing factors were discussed in the paper.Themajor work that has been completed is as follow:Based on the investigations of ballastless track slabs at Chenggaozi Station ofHaerbin-dalian railway and Chongqing Caijia Station of SuiYu railway, performancesof the CRTS I ballastless track slab and two-layer two-way pre-tensioned prestressingballastless track slab under the influence of temperature, dynamic load and unevenrailway subgrade settlement were summarized. Damages of the slabs were recorded andanalyses were carried out. Major conclusions obtained form the investigations are asfollows:(1)Due to inappropriate structure design and unsatisfactory materialprosperities, many prestressed bars fractured and seal anchors dropped off. Cracksappeared a lot especially on the influence of uneven railway subgrade settlement.(2)Pre-tensioned prestressing ballastless track slabs performed well in terms of cracks,however, rust were observed at the end o f prestressed bars.CRTS I and CRTS II as well as two-layer two-way pre-tensioned prestressingballastless track slabs were tested to investigate the mechanical behavior. The staticloading tests of three kinds of slabs were made to determine the static bearing capacityand verify the performance of the prestressed steel. Midspan load-displacement curveand strain history curve were used to analyze the results. Based on the test results, thefollowing conclusions can be obtained:(1)The two-layer two-way pre-tensionedprestressing ballastless track slab has better performances than the other two kinds ofballastless track slabs on the yield load, prestressed effect and cracking sensitivity.(2)The economic benefit of pre-tensioned prestressing ballastless track slab is obviouslyhigher than others owing to its lower steel content. The change of temperature will cause stress and deformation in ballastless trackslabs. The slab warpage under repeated influence may cause the damage to the trackslab system. Accroding to the finite element analysis, the mechanical behavior oftwo-layer two-way pre-tensioned prestressing ballastless track slabs under the affect oftemperature was analysed and its influencing factors were discussed. The influencingkey factors of the structure mechanics response were studied respectively, whichcontain the degree of prestressing, non-prestressed steel, thickness of CA layer andfriction coefficient on the contact surface. According to the analysis results,severalsuggestions and measurements were proposed to control the adverse effect on two-layertwo-way pre-tensioned prestressing ballastless track slabs under different temperaturegradients.