Hydro-thermo-mechanical analysis of early-age temperature and humidity evolution in double-block ballastless track slabs

The temperature and humidity characteristics during the concrete construction stage of the double - block ballastless track slab have an important influence on the mechanical behavior of the track slab after forming. To conduct an in-depth study on the mechanical behavior of the double - block ballastless track during the construction period, a humidity -temperature - mechanics model of the double - block ballastless track was established in this paper by using the humidity - temperature mechanics coupling method. Through numerical simulation and test, the variation laws of humidity, temperature, and mechanical behavior of the double - block ballastless track during the construction period were revealed. The test results showed that the internal temperature of the concrete track slab reached its peak on the third day and then decreased. The humidity maintained a relatively high level during the water storage curing period, and the surface humidity decreased rapidly after 14 days, forming a humidity gradient from the surface to the interior. The simulation results showed that the changes in humidity and temperature of the ballastless track slab with the concrete age were both very obvious, and at the same time, the non uniform distribution of temperature and humidity would cause the initial stress of the structure. Extrapolation results based on numerical simulation show that both the increase in the daily average temperature and the increase in the wind speed would intensify the differences in humidity and temperature between the surface and the interior of the ballastless track slab, thereby inducing greater thermal stress and humidity shrinkage stress. Therefore, during construction, measures such as covering and moisture preservation should be taken according to the changes in temperature and wind speed to reduce the adverse effects of environmental factors on the track slab. • A humidity-temperature-mechanics model for double-block ballastless track construction is established. • Variation laws of humidity, temperature and mechanical behavior during construction are revealed via simulation and test. • Non-uniform distribution of temperature and humidity induces initial structural stress in track bed. • Environmental factors like daily average temperature and wind speed intensify thermal and humidity shrinkage stress.