Analysis Of The Interface Damage Of CRTS? Slab Track And Its Influnces

Currently, CRTS ? slab track is one of the main non-ballasted track structure which has been widely applied on Chinese high-speed railway. It can be seen from the operation practice that the operation safety, stability and comfort are very well when the high-speed train is running on the CRTS ? slab track railway. However, the variety damage of track structure components and the connection between them would inevitably occur under the influence of dynamic train load, temperature and environment. Among them, the interface damage between the CA mortar and the track slab or base slab (supporting layer) is the typical interface damage, and at the same time it is one of the most prominent diseases of CRTS ? slab track. The path of force bearing and transferring will be changed due to the interface damage, it may have an impact on the carrying capacity, functionality and durability of non-ballasted structure system. At present, there is a lack of systematic studies on interface damage of CRTS ? slab track. Based on the summary and absorption from former researches, starting with the perspective of damage and combining with the structure characteristics of CRTS ? slab track, the cohesion theory and the concrete plastic damage model are introduced into the related calculation model, the research of interface damage mechanism and the influence of post-damage on the running safety and the strength and stability of track structure are conducted.The main work and results are as follows:1. Based on the site investigation and relevant literature, the basic characteristics of early disease and the properties of interface damage of CRTS ? slab track are summarized.According to the site investigation of under-construction and operation line, the main form and the basic characteristics of early disease of CRTS ? slab track are summarized. Based on the relevant literature and combining with the structure characteristics, the main diseases of CRTS ? slab track are divided into two types, the inner damage in structure layer and the interface damage between structure layers. The characteristics and cause of interface damage are preliminary analyzed, which provides basic data for further research.2. The nonlinear finite element analysis model of coupling damage between the inner-layer damage and the interface damage is established through finite element method.According to the structure features and its interlayer damage characteristics of CRTS ? slab track, the discrete finite element model with considering the influence of inner layer and interface coupling damage is established through nonlinear finite element method, the inner-layer damage and the interface damage are simulated with concrete damage plastic model and cohesion theory model respectively in this model. The interface damage parameters are determined by indoor test and simulation. Using the ABAQUS commercial software, the model realization and analysis method are systematically expounded, and the corresponding calculation program DABT-S is programmed through PYTHON. The numerical analysis examples are performed with DABT-S and its corresponding analysis are discussed, the correctness of nonlinear finite element model, calculated method and the program correctness are also verified, which provide a foundation for the analysis of interface damage mechanism and its influence subsequently.3. Based on the calculation model of coupling damage between the inner-layer and the interface damage and the analysis method of interface damage propagation, the analysis of interface damage under temperature load is carried out.The production and propagation of interface damage were analyzed during three differe nt forming stages of pre-longitudinally-connected, longitudinally-connected process and post-rail-laying respectively, and its influence on the structure stress and deformation was discus sed.Research results show that:(1) During pre-longitudinally-connected stage, under the action of temperature gradient, the interaction between the layers is very strong, the oversize interlayer stress or the insufficient strength and toughness of interface would cause type I and type II compound injury. Meanwhile the incorrect construction would accelerate the injury emergence and development. Under the positive temperature gradient load, the lower surface of track slab is in a very worse condition to bear force during the propagation process of complete interface debonding damage, especially for the front area of damage. (2) During the process of longitudinally connecting, before casting wide-narrow juncture, long stagnation between each working procedure may change the overall temperature load to cause interface damage; after casting wide-narrow juncture, damage usually does not occur between interlayers when there is no defect in the layer. (3) In the operation stage, the interface damage may happen under the negative temperature gradient load because of the insufficient interlayer strength, wide spacing of pre-splitting crack and deficient connection area of wide-narrow juncture, etc. Under the load of increasing temperature, low interlayer strength, eccentric flaws of wide-narrow juncture are the main reasons of interlayer damage, especially the latter reason will cause bigger upwarping deformation at track slab, delamination damage and over-limit fastener fulcrum counterforce, etc. It is suggested that the elastic modulus of the narrow juncture should be no less than 10GPa in engineering.4. On the basis of the calculation model of coupling damage between the inner-layer damage and the interface damage and the analysis method of nonlinear buckling, the analysis of nonlinear buckling involving interlayer damage evolution was conducted.Aiming at the longitudinal stiffness heterogeneity distribution caused by the constructio n and defect, the non-liner buckling characteristics of CRTS ? slab track with inner-layer de fect was analyzed, in this analysis progress the production and propagation of interface dama ge under the load of increasing tempreture were taken into account. Then the influence of dif ferent defects with interface debonding damage on nonlinear buckling characteristics is studi ed. It can been seen from the research results that:(1) under the temperature and pressure load, the nonlinear buckling of track slab occurs with the interface debonding damage. Post-buckling strength is larger when there is no defect in the layer, but interaction coupling between the inner-slab damage and the interface damage at the eccentric defect position of wide-narrow juncture gradually expands and evolves; the vertical bending stiffness of track structure significantly reduces, while the buckling deformation increase, and the crevice hapens between interlayers, which changes the force bearing and transferring model of track structure; upwarping deformation causes the change of fastener fulcrum counterforce distribution, and upwarping area force easily exceeds the design value of clamping force of fastener when buckling deformation is large. (2) The eccentric defect in track slab is the main cause of inner-layer and interface damage, buckling deformation and mechanical deterioration of track structure, in addition, initial debonding damage, deficient bond strength between layers, initial damage or defect of track slab, and initial irregularity of rail are also the important factors of the nonlinear buckling, so the track structure may lost stability under the action of multiple factors. (3) The initial suggestion is that the interlayer debonding length should not be more than one fastener spacing at 0.65 m.5. Based on the wheel-rail dynamics theory, vertical coupling vibration model with considering the influence of temperature and damage is built, and the influence of wheel-rail dynamics characteristics on the interlayer damage is studied.According to the dynamics principle of wheel-rail system, the vertical vibration coupling model of train and slab track with damage under the coupling action of temperature and train load is established through finite element method. Using the commercial software ABAQUS, VIWR, the wheel-rail interface interaction subroutine is compiled through FORTRAN, and the corresponding dynamic analysis program, DABT-V, is compiled through PYTHON. The model and program was confirmed to be reliability by the comparison between the example analysis and the field test. Using the established model and program, the interlayer damage propagation and development under the train load was analyzed, and the influence of interlayer debonding damage and upwarping deformation on the wheel-rail nonlinear dynamic characteristics was studied. The results reprenst that:(1) the influence of train load on the expansion of interface damage is small, but damage may expand under the combined effect of temperature and train load, especially under the increasing temperature. (2) the interlayer debonding damage without gap has a small impact on the wheel-rail dynamic characteristics, while the damage with gap will have a significant impact on the wheel-rail dynamic characteristics. (3) because of the irregularity of track structure caused by the eccentric defect of wide-narrow juncture under increasing temperature, the large second impact will be produced when trains passing, it has an adverse impact on the wheel-rail system dynamic characteristics, especially on the fastener fulcrum force, and in severe cases of that the complete load reduction which affects operation safety may occur...