Effects of joint stiffness degradation on vertical stability of CRTSII slab ballastless track

Joint damage of the China Railway Track System (CRTS)II slab track leads to typically non-uniformity of the longitudinal stiffness of the track slab, which tends to produce different degrees of arching at the joint. The objective of the present study was to investigate the arching mechanism of the non-uniform track slab. The buckling eigenvalues and arch curves of the non-uniform track slab were obtained using the Newton iterative eigenvalue algorithm. An analytical expression for the equilibrium path of the slab with an initial arch was obtained using the energy method. Then, the arching law and stability of the non-uniform track slab were analysed. The following results were obtained. 1) The reduction of the joint bending stiffness significantly affects the arching deformation and buckling mode of track slab, thus, it is necessary to consider the non-uniform characteristics of the track slab when analysing its stability. 2) The most unfavorable wavelength of track slabs is between 6 m, and 7.5 m considering the different joint bending stiffnesses and elastic moduli, and the reduction of the bending stiffness of the joint is the main factor for reducing the most unfavorable wavelength. 3) The reduction of the joint bending stiffness is the most important factor for causing the instability of the track slab, the maximum allowable temperature rise decreased from 83.97 to 49.12 celcius when the bending stiffness of the joint was reduced by a factor of 100. 4) For improving the stability of the track slab, releasing part of the temperature force in the track slab by reducing the elastic modulus of the joints is a feasible method, the maximum temperature rise of track slabs can be rapidly increased when the elastic modulus of the joints is < 5000 MPa.