Experimental and Statistical Analysis of the Vertical Temperature Gradient, for Ballastless Railway Track, in Alpine and Plateau Environs

Temporal temperature evolution of ballastless railway track is a random process caused by complex environmental actions. The vertical temperature gradient (VTG), varying continuously with time, has significant effects on the repeated deformation of ballastless track. However, few researchers have considered the statistical analysis of VTGs in alpine and plateau environs characterized by high altitude, strong solar radiation and high diurnal temperature differences. In this study, a temperature field test platform of ballastless track was established in Shannan City, Tibet and the temperature field of ballastless track was measured. Based on four statistical methods, a Monte Carlo simulation (MCS), Gaussian mixture model (GMM), Generalized Pareto distribution (GPD) and a third-order polynomial normal transformation technique (TPNT), the VTGs of ballastless track in alpine and plateau areas, are statistically analyzed. The results show that the applied statistical methods, used for predicting the VTG representative value, in ballastless track, are feasible within different application conditions. The recommended positive and negative representative values of the VTG of ballastless track are 91.58 degrees C/m and -40.15 degrees C/m, and 82.83 degrees C/m and -35.03 degrees C/m, with failure probabilities of 1% and 5% respectively, in alpine and plateau areas. The research results can provide a reference for the design and maintenance of ballastless track used in alpine and plateau environs.