Editorial for the Special Issue “Artificial Ground Freezing Technology”

Artificial Ground Freezing (AGF) has evolved into a cornerstone technique for geotechnical engineering, offering robust solutions for ground stabilization, seepage control, and infrastructure development in challenging environments [1,2]. As climate adaptability and sustainable construction practices gain urgency, AGF’s role in tunneling, mining, and permafrost preservation has become increasingly pivotal. The origins of Artificial Ground Freezing (AGF) trace back to the mid-19th century, when German engineer F.H. Poetsch first patented the technique for shaft sinking in waterlogged soils. By the early 20th century, AGF had gained traction in mining and tunneling projects across Europe and North America, notably stabilizing the soft grounds of the Paris Métro. Artificial Ground Freezing (AGF) technology was first introduced in China in the 1950s, primarily for mining applications in water-rich strata. The 1970s marked a turning point with the advent of computational modeling, enabling precise thermal and mechanical predictions. China began adopting AGF for urban metro construction, with early trials in cities like Beijing and Shanghai. A major breakthrough came in the 1990s with the Huangpu River Tunnel project in Shanghai, where AGF successfully stabilized soft soil under high hydraulic pressure. Since the 2000s, China has pioneered innovations such as local horizontal freezing and energy-efficient freezing systems, driven by rapid urbanization and complex geotechnical challenges. Today, China leads in large-scale AGF applications, from permafrost engineering in Tibet to mega-city underground expansions, making it a global hub for frozen ground research and technology.

This Special Issue presents cutting-edge research on Artificial Ground Freezing (AGF), covering thermal modeling, the mechanical behavior of frozen soils, environmental interactions, and the optimization of freezing techniques. The contributions can be categorized into four key themes:

• Thermal Process Optimization and Numerical Modeling

Pang et al. and Duan et al. analyzed 3D temperature fields and steady-state solutions for freezing pipes, improving frost heave predictions in seepage-prone strata (Li et al.). Hu et al. optimized cooling schemes using finite element analysis, while Ou et al. numerically assessed the ground movement induced by freezing walls. Peng et al. developed an elastoplastic theory for horizontal frozen walls under non-uniform loads.

2.

Mechanical Behavior of Frozen Soils and Rocks

Wang et al. and Rong et al. [3] investigated freeze–thaw deformation in soil–rock mixtures and calcareous clay, revealing critical influencing factors.

Zhou et al. studied pore evolution in saturated silt, while Shu et al. established a constitutive model for frozen sandstone. Wang B. et al. [4] and Bublik et al. examined the elastoplastic properties and saline soil’s effects on frozen wall stability.

3.

Environmental and Geochemical Interactions

Ivanova et al. [5] explored biogeochemical partitioning in permafrost peatlands, linking AGF to climate impacts. Batoćanin et al. analyzed tufa deposits, bridging AGF with hydrogeological processes.

4.

Advanced Applications and Sensitivity Analyses

Wang T. et al. conducted a hydrothermal sensitivity analysis for soft clay, aiding AGF design in variable conditions. Zhou et al. and Li et al. assessed seepage effects and frost heave distribution, enhancing tunnel freezing techniques.

This Special Issue provides a comprehensive basis for next-generation AGF applications in urban tunneling, permafrost engineering, and sustainable geotechnics. Within it are compiled 16 innovative studies that push the boundaries of AGF research—spanning numerical modeling, experimental mechanics, and field applications—to address critical gaps in energy efficiency, frost heave mitigation, and long-term performance. It explores cutting-edge advancements in AGF technology, from numerical modeling and thermal process optimization to case studies highlighting its application in extreme environments. By compiling interdisciplinary research, we aim to address critical challenges—energy efficiency, long-term performance, and climate adaptability—while fostering collaboration between academia and industry to shape the future of frozen ground engineering.