Numerical and Experimental Study of High-Power Microwave Heating for Fracturing Permafrost in Extreme Cold Regions

Infrastructure development in extreme cold regions poses ongoing challenges primarily due to the high rigidity of permafrost caused by its ice content, but traditional heating methods fail and lack scalability. Here, we introduce microwave heating technology to unlock new solutions for parallel, high-intensity permafrost fracture. We innovatively designed a horn antenna array with electromagnetic shielding and a mobile transmission system, delivering up to 5 kW microwave heating power. Using COMSOL simulations, the 3×4 microwave array is determined, the matching layer function is illustrated, and the heating distance is evaluated. After 15 s of microwave heating, the temperature at a depth of 400 mm in the permafrost obviously increases. Then, these qualitative simulation results are used to guide the experimental process, such as applying a matching layer, adjusting the radiation distance, and avoiding power loss. In prototype experiments, the fracturing efficiency of permafrost increases by about 60% as water content rises from 20% to 40%, but fracturing efficiency decreases at low temperatures. With a microwave input power of 5 kW, the electric field strength reaches 104 V/m, and the volume power density reaches 107 W/m3, fulfilling the fracturing criteria in the simulation. The fracturing effect is further validated by pressure resistance and shear resistance testing on samples at 293.15 K and 313.15 K. This work undertakes numerical simulations for fracturing permafrost using high-power microwave heating, explores the electromagnetic-thermal coupling effects, and experimentally demonstrates its application in fracturing permafrost. These practical engineering results provide valuable insights for microwave heating-induced permafrost fracturing scenarios.