Interface Failure Analysis Of Double-block Ballastless Track In High-speed Railway Under Joint Actions Of Train And Environment Loads

The double block ballastless track structure has been widely used in China.Through the field investigation,it is found that the seam between the roadbed slab and the support layers has appeared in many lines,The formation of seam will lead to the power transmission mechanism between the layers of the double block ballastless track changing,it is a serious disease which could affect the stability and durability of the track structure,that could even affect the running stability and driving safety of the high speed train.Therefore,the analysis of the interlayer bonding failure behavior of the double block ballastless track under high-speed railway train load with environment composite effect is carried out in this paper.which analyzed by aiming at the characteristics of the double block ballastless track subjected to the complex interaction of the train load with the environment and combining with the latest application of the interface mechanics in ballastless track damage and failure study.The analysis has revealed the characteristics of interface failure and interlayer clearance expansion which could provide reference value for improving the design theory and maintenance technology of double block ballastless track.The accomplishment of this paper relies on the support of the national key basic research development plan(973 Plan)project,"dynamic performance evolution of high speed railway basic structure and the basic research on service safety(2013CB036200)".And the following research work was conducted1.The characteristics of interface under high-speed railway train load with environment composite effect and interface failure are analyzed.According to the research,the mechanical behavior of ballastless track interface,the interface failure and interface mechanics performance experiment and the train load with environment composite effect on the failure of ballastless track like such issues are discussed,which play the key role of the research in this paper.2.The interface bond strength test and the concrete interface tensile fatigue performance test of roadbed-surpport layer is conducted by making roadbed-surpport layer concrete composite specimens of high speed railway double block type track and designing the related test plan,The interface failure pattern is proved and the key parameters of double block ballastless track interlayer bonding interface model are determined,and the interfacial tension fatigue s-n curve is obtained through the test.3.The bonding interface model of double block ballastless track interlayer was established at first,and the validity of the interface model was verified by comparing with the test results.Then the double block ballastless track finite element model considering interlayer bonding failure was established by embedding the interface model into cohesion unit,the model is the base of analyzing the interface bonding failure performance under composite affection circumstance which including train load,temperature gradient,and seam water.Then,the coupling dynamics model of high speed vehicle-double block ballastless track is biult by using vehicle-track coupling dynamics theory to solve the rail force.According to the requirement of temperature gradient analysis,a temperature gradient calculation model of double ballastless track roadbed slab is modeled by using heat transfer theory.A dynamic hydraulic pressure calculation model which based on the fluid-solid coupling theory is established for analyzing the hydrodynamic action of the seam water.Those two kinds of models is verified respectively.The results show that the interface model and the train load-environment composite affect model the writer have modeled are reliable and effective.4.Through applying the temperature gradient calculation model of double block ballastless track roadbed slab,the annual temperature gradient values of roadbed slab acquired through the calculation,the mapping relationship between the interfacial tension of double block ballastless track and the temperature gradient is studied,and the law how the related parameters influence interfacial tension acquired by carrying out through long-term interfacial tension fatigue analysis considering the condition with temperature gradient,meanwhile the stress,damage and displacement distribution of interface while impact damage occurred in interface is analyzed.The results show that there is a mapping relationship between interfacial tension and temperature gradient of ballastless track.The distribution of interfacial fatigue tension has obvious regional characteristics.With the increase of temperature gradient load,the variation of cohesion stress and displacement in interface presents three stages: linear elastic rise,damage evolution and failure.When the Interface under temperature gradient load and impact damage occurs,the interface normal damage takes the dominant position in compound damage when the interface under impact damage which subject to temperature gradient load action,the lower bonding performance of the interface has,the more prominent that the dominant position of normal damage in composite damage takes.5.The spatial and temporal distribution characteristics of hydrodynamic water pressure in the seam of double-block ballastless track subjected to train load are studied by using interlayer seam hydrodynamic water pressure calculation model.Then,the spatial and temporal distribution of interfacial tension of single section of vehicle is analyzed.And the interfacial fatigue tension while the vehicle passing through is obtained by simplifying the former analysis.Finally,the spatial and temporal distribution characteristics of interlayer bonding state while interface impact failure occurs are analyzed,and the critical depth of interlayer seam during impact failure under different clearance height and train running speed is obtained.The main conclusions are as follows: under the action of train load,the maximum positive pressure value of hydrodynamic water pressure is reached when the 3rd-position wheel pair of high-speed vehicle passes,and the maximum negative pressure value of hydrodynamic water pressure is reached when the 2nd-position bogie midpoint passes.There may be both positive pressure and negative pressure exist at different depths of the warter seam at the same time,.When the high-speed vehicle passes directly above the interface,the interface is closed under pressure action;when the 4th-position wheel pair arrives above the interface,the interface pressure value reaches the maximum;The interface tension reaches the maximum value when the vehicle passes through the interface.As the seam depth increases gradually,the seam height decreases gradually and the train operation speed enhances gradually,the maximum positive value of dynamic water pressure of vector and moment,interfacial tension increases gradually,while the maximum negtive value reducing gradually.The impact damage of the interface has short action time while the damage is large.The impact damage occurs when the vehicle passes through the interface and the seam depth expands to 0.18 m.When impact failure occurs at all points of the interface while the train runs at a speed of 350km/h,the height of the seam is 2mm,and the depth of the seam is 0.9m,,the interfacial normal failure takes the definitely dominant position of the compound failure when the impact damage occurs in the interface.6.The full process of interface damage while the track under the composite cirsumtance with both train load and environment affect is studied,first of all the conditions of the initial damage occurs in the interface under the extreme condition is found out,then the interface fatigue damage analysis method is put forward,and next the range service life of interface is obtained by calculating the living example which adopting the analysis method and combining with the meteorological data in 2001 in guangzhou region,.Finally,the evolution rule of dynamic performance of rail structure is acquired through the evolution relationship among dynamic performance of rail structure with the separation depth and interface life.The main conclusions are as follows: While the calculation model under extreme conditions,the initial interface failure will occur when the temperature gradient value and the interface bonding performance value at an unfavorable combination condition,.The effect of fatigue damage on interface is distinct at different cracking depth,.Fatigue failure is not easy to occur at the interface within a depth of 0~0.3m.The initial depth of clearance is an important factor that affects the evolution of dynamic performance of track structure.Water accumulated in the seam could dramatically accelerate the deterioration process of dynamic performance of track structure.The displacement of rail and roadbed slab reaches unqualified criteria of the standard under the long-term effects of train loads and environment about 25 years(when there is a water away from the seam)or 34 years later(when there is no water from the seam)respectively when the initial seam depth at 0.6 m.If the initial seam depth is 0.7m,the time when the displacement of rail and slab exceeds the standard would be 5 and 13 years respectively.