This study focuses on permafrost degradation on the Qinghai-Xizang Plateau under warming and humidification. Using numerical simulations combined with geological surveys and environmental monitoring data from the G0615 Dema Expressway (Xiangride to Huashixia section)

the research analyzes how water infiltration accelerates ground ice melting in silty clay layers and the evolution of hydrothermal states. The results indicate that underground ice melting occurs in four distinct stages: rapid temperature rise due to heat absorption by ice

stable temperature rise during the ice-water transition

rapid temperature rise of ice meltwater

and stable temperature rise of ice meltwater. Water infiltration significantly improves heat transfer efficiency at the ice-soil interface

leading to an initial increase followed by a decrease in the cooling range of surrounding soil. Additionally

higher infiltration rates cause the cooling range peak to occur earlier. Underground ice redirects water infiltration

but its melting gradually reduces the obstruction to seepage. For a constant cross-sectional area of ground ice

the time for complete melting decreases as it transitions from a vertical to a horizontal state. Horizontal ground ice melting exerts a greater influence on the temperature and seepage fields of surrounding soil

driven by factors such as hydration heat

ice-water transition

and dynamic infiltration path adjustments. This research offers a theoretical foundation for understanding the catastrophic melting of permafrost on the plateau under warming and humidification

supporting the development of more precise underground ice melting prediction models.