Experimental Investigation of Geothermal Ice-melting Efficiency on Pavement at Highway Tunnel Entrances in Cold Regions

Rapid and efficient de-icing methods are essential to ensure vehicle safety at highway tunnel entrances in cold regions. While geothermal ice-melting technology offers environmental and sustainability advantages， its application in tunnel entrance scenarios remains limited. To address this gap， a four-factor， three-level orthogonal ice-melting experiment was designed to systematically evaluate the ice-melting efficiency of a geothermal hydronic heating system under simulated cold-region tunnel conditions. Key variables included ambient temperature （-7.5℃--12.5℃）， fluid temperature （40-60℃）， wind speed （4.5-6.5 m/s）， and preheating duration （0-4 h）， were tested in a controlled large-scale laboratory. Ice-melting efficiency was quantified by the time required to achieve a melting ratio of 0.7 for a 10 mm thick ice layer. Results identified ambient temperature (T_a) and fluid temperature (T_f) as dominant factors， with T_f=50℃ serving as a critical operational threshold. Lower T_a prolonged the efficient ice-melting period due to increased convective heat loss， while higher wind speeds （6.5 m/s） enhanced sublimation-driven melting. The process was categorized into four distinct phases: initial， rapid， accelerated， and stabilization. Notably， pavement temperature stabilization preceded ice-melting rate equilibrium， and complete melting occurred even when surface temperatures remained sub-zero. These findings provide practical recommendations for optimizing geothermal system parameters in cold regions.