The thermal regime evaluation of high-speed railway foundation by mixed hybrid FEM

The construction of high-speed railways in permafrost and seasonally frozen regions will disturb the local heat balance and affect the original thermal regime significantly. The accurate evaluation of thermal regime is the critical step of frost heave and thawing settlement predictions. In order to evaluate the thermal regime precisely, we adopt a modified Finite Element Method which is called as Mixed Hybrid FEM (MHF) in this study. MHF allows simultaneous computation of side temperature, element temperature, and heat flux. Since freezing rate can affect the accuracy of frost heave prediction, therefore direct element temperature obtained by MHF is highly significant for improving the accuracy of frost heave evaluation. In the thermal analysis, we consider the phase change of water and the latent heat influence by equivalent heat capacity method. To demonstrate the applicability of MHF in the application of thermal regime simulation, we compare the numerical simulation results obtained by MHF with field monitoring data from high-speed railway foundation. The real field monitoring data from high-speed railway foundation demonstrate that, under sine-curved air temperature changes, MHF shows a good accuracy for the thermal regime evaluation in high-speed railway foundation. Also, through the numerical simulation results of MHF, we compare the freezing depth in the first and second year to verify the influence of the construction to the thermal regime of natural ground. Through this study, we demonstrate that MHF could be applied for the thermal analysis of high-speed railway foundation successfully. The construction of high-speed railway increases the freezing depth in the first year. Moreover, we recommend adopting the MHF in the thermal analysis of frost heave and thawing settlement evaluation model due to its promising advantages.