Thermal effect of the accumulated water with different depths on permafrost subgrade in cold regions

In cold regions, the thermal effect of accumulated water on underlying permafrost and permafrost subgrade remains a significant hazard causing engineering risks. Water depth of accumulated water may be an important influence factor of permafrost thermal stability, but there is lack of qualitative and quantitative research about that. In this study, equivalent thermal conductivity theory and solid heat transfer theory have been used to establish the calculation model for simulating heat transfer in water and soil. Thereafter, the accuracy and reliability of the calculation model are checked by monitored data and subsequently used to analyze the thermal erosion of water on underlying permafrost and permafrost under the embankment. These simulation results show that shallow water can protect permafrost and deeper water disrupts the thermal stability of underlying permafrost. The thermal effect extent of water is primarily determined by its depth, and the concept of critical depth and stable depth of accumulated water has been proposed. Moreover, the temperature field of permafrost under embankment can be changed by the slope toe water. In addition, the thermal effect range of the slope toe water is limited by the thermal influence radius, which increases with the depth of standing water. These findings provide support as well as a fundamental base for environmental issues arising from the accumulated water. These observations will, thus, also be valuable to further engineering environment studies in cold regions.