Study on the mitigation effect and mechanism of solar heating subgrade system on frost heave of railway subgrade in cold regions

Frost heave represents a significant factor influencing the smoothness of railway track and the long-term service performance of subgrade in cold regions. The solar heating subgrade system (SHSS) represents a promising approach for mitigating subgrade frost heave. However, the mitigation effect and mechanism of SHSSs on subgrade frost heave remain unclear. In this paper, the mitigation effect and mechanism of SHSSs on subgrade frost heave were systematically analyzed by numerical simulation. Finally, the application effect of SHSSs combined with insulation materials in the subgrade of the Xining-Golmud section of Qinghai-Tibet Railway (QTR) was evaluated by field test. The numerical results demonstrate that the reduction in the freezing rate (by 85 %) and the freezing depth (by 95 %) of the heating subgrade, which results in a decrease of moisture migration and ice lenses formation, is the primary reason why SHSSs can make the frost heave less than the permissible frost heave value of 5 mm. The monitoring results in the subgrade of Xining-Golmud section of QTR also indicate that SHSSs combined with insulation materials can reduce frost heave from 22.5 mm to 5 mm, and significantly reduce the lateral differential deformation of subgrade.