The coupling effect of environmental temperature and moving train loads significantly impacts the mechanical performance of ballastless tracks on intercity railways. To further explore the thermal performance of double-block ballastless tracks (DBBTs) under complex temperature conditions, an initial test was conducted on a 1/4 geometric scale DBBT model across three temperature scenarios. Following the validation of these experimental results, thermal-mechanical coupling models for two types of DBBTs (unitized and longitudinal) on subgrades with two different boundary constraints were developed. These models aimed to examine their mechanical responses under train speeds ranging from 120 km/h to 200 km/h and their interaction with high daily temperatures. The findings indicate that temperature change rates in the track slab are significantly higher than those in the supporting layer, with the stresses in the limiting groove and supporting layer being the highest and lowest, respectively. The relationship between temperature and stress in the track slab follows a second-order quadratic polynomial. Additionally, measured longitudinal displacement results are smaller than theoretical predictions, especially under dropping temperatures. Furthermore, under all three train speeds, both dynamic stress and displacement are higher in the longitudinal DBBT than in the unitized DBBT. The coupling effect of temperature and moving train loads notably increases the dynamic stress in both types of DBBTs, with a more pronounced effect on the dynamic displacement of the longitudinal DBBT compared to the unitized DBBT.