Failure Analysis And Experimental Study Of Damage For CRTS? Ballastless Track Structure In High Speed Railway

With the development of railways in China,a large number of high-speed railways were conducted during these years,and the construction of high-speed railway has entered a new stage.However,rapid development of high-speed railway also brings problems and challenges at the same time.A certain degree of defects such as cracking?uplifting?warping of concrete base and track slab during the service in several high-speed rail lines caused by the lack of theoretical research on performance of ballastless track structure(BTS).It is very significant to conduct research on the defects of BTS which had a serious impact on the operation safety of high-speed railway.In this dissertation,indoors experiment,theoretical analysis and numerical simulation were carried out to analyse the failure modes of BTS based on the CRTSII which used in Beijing-Shanghai High-speed Railway.The studies were the summary of previous research results,and supported by the Funding of "Study on the design theory and method of whole life based on reliability of the BTS".Firstly,mechanical analysis of BTS was carried out with detailed models which considered the material,load and boundary condition to research the most unfavorable position and potential failure mode.The results show that:the critical load of BTS which is established on the subgrade is at the end slab of type CRTS ?,but the one which is established on the foundation of bridge is at the end loads in the middle of span,and the most unfavorable position of track slab is at the corner of the slab.The most unfavorable position of CA mortar layer and support layer/base plate is below the load.However,for BTS of type CRTS ?,the critical load of track structure is in the middle of slab,the most unfavorable position of track slab,CA mortar layer and support layer/base plate is below the load.Secondly,cracking caused by uniform cooling and the gap between the track plate and the lower support structure due to the temperature gradient was paid more attention based on a new calculation method.A cracking models considering the constraint effect of the reinforcement,lower support structure(CA mortar layer or self compacting concrete layer)and the shrinkage deformation of the upper fastening system was developed to analyze the formation mechanism of BTS under uniform cooling.Based on the method of energy method,using a Fourier series to simulate the warping curve of track plate,obtaining the curve equation of the track slab according to the quasi Newton iterative algorithm,the warping deformation of track plate under different temperature gradient and ground coefficient were studied,eventually,the method for reducing the warping of the slab was discussed.Subsequently,the reliability theory for the safety analysis of BTS was applied.Failure mode of longitudinal and transverse bending tensile of BTS under train loads was analyzed.Then,a reliability index to indicate the risk of structural was established for determining the failure path to achieve safety evaluation quantitatively.Failure probability analysis method of the longitudinal connection track slab under the cooling was established based on reliability theory and distribution characteristics of crack spacing and width under random parameters were investigated.Again,the experimental study on mechanical properties of CRTSII slab under static load were carried out.According to the mechanical properties of the track slab,carrying capacity test was studied on different experimental slabs of bottom sections,mid-span sections and longitudinal sections respectively.Based on the analysis of the test data the crack distribution,failure mode,bearing capacity and the calculation method of crack width and section stiffness were discussed.Finally,a three-point bending test was carried out to obtain the relationship between load and deflection under step load,strain of mid-span section and its height,the curvature and its damage,then the damage evolution process of track slab under different crack width was also analyzed.A damage probability evolution function of BTS was conducted with curvature,which can be evaluated structural damage degree with curvature of the track slab.