Study On The Gap Occurrence Mechanism And Its Influence On Train Of CRTSⅡ Slab Ballastless Track Structure

Through field investigation of CRTSⅡ slab ballastless track structure damage, determined the typical gap between slab and CA mortar at the end and middle of slab as research object. Analysed and summarized research status about the gaps, showed the necessity of research. Came up with an idea to research ballastless track damage,that is combining fatigue analysis and extended finite element method to study the gap damage based on finite element modeling analysis.In the meantime,established train-track-bridge coupling model,analysed the gap influence on train. The main research work and achievements are as follows:(1) Investigated CRTSⅡ slab ballastless track structure damage,found the gaps easily occurs at the end and middle of slab, in the meantime,there is some white outflow when the gap has not occurred,and the serious damaged area CA mortar is damaged or appeares some holes.(2)On the basis of analyzing the existing research results, determined adopting finite element model to analyze the stress of the mortar layer, using force analysis results for mortar layer fatigue life analysis,introducing extended finite element method to study the gap developing process based on fatigue analysis identified low service life area.(3)Through the analysis of the stress and deformation of the track structure finite element model under temperature load.The results show that, temperature gradient effect is one of the important factors lead to gap, positive temperature gradient leads to track slab occurring dent deformation, the "M" deformation occurs both in length and breadth of the slab, extremity positive temperature gradient affects most the area between sleeper and slab side. Extremity negative temperature gradient affects most the area between sleeper and slab side too, the "W" deformation occurs both in length and breadth of the slab,so temperature gradient leads to the gap.(4)The fatigue life analysis of CA mortar shows that if initial damage exists the life will be reduced, and service life will gradual decline if the elastic modulus increases. From this, the severe gaps at the beginning of the high speed railway operation due to initial CA mortar damage.So increasing elastic modulus of CA mortar to inflict damage is more suitable for fatigue life analysis of mortar layer.(5)Simulated and analysed development process of CA mortar gap at the slab end edge,slab end middle and slab middle edge based on extend finite element method.Found that the gaps develop ealily along longitudinal direction under temperature load, then form through gap along the whole track slab length step by step. Contrastive analysed the gap area (GA)in that 3 kind working condition,found that the GA increases gently in the initial stage when gap starts at the slab end,that is, gap develops slowly in the intial stage while rapidly in the later period.And the GA increases more fast from the intial stage when gap starts at the slab middle, rises perpendicularly.So, the gap damage prophylaxis and treatment should start at the intial stage in case its rapid expansion in the later period.(6)Put forward a gap damage prevention measure,that is, do seal processing on exposed CA mortar on the side of track structure and the gap between track slab and wide joint seam,this measure will have important reference value for the prevention of CA mortar damage.(7)Analysed the gap damage influence on train operation through the established train -track-bridge coupling dynamic model.The results show that, a small scale gap damage has smaller influence on the safety of train operation, the derailment coefficient and wheel load lightening rates are only a small increase, mainly affects vertical acceleration,and the peak value increases along with the increases of gap length,so the gap damage mainly has influence on riding comfort, needs repair in time.