Development and prospect of freezing shaft lining technology for vertical mine shafts in China

This paper delves into the formidable challenges posed by the trends of “deepening” and “scaling up” in the design, construction, and operation of deep mine shafts in China. By synthesizing experiences and lessons learned, it underscores that the freezing method for shaft sinking stands out as the paramount technique for groundwater sealing and formation reinforcement in deep shaft construction amidst complex geological conditions. Additionally, it reviews the state of domestic and international advancements in Freezing Shaft Lining Technology (FSLT) prior to 2002. Furthermore, the paper offers a comprehensive overview of the remarkable advancements and applications of FSLT in deep soil layers spanning from 400 m to 800 m and in deep water-rich rock layers ranging from 500 m to 1 000 m in China since 2002. These include the design and construction technology utilizing C60～C100 or CF80～CF110 high-strength concrete for freezing shaft lining, technologies for preventing and controlling shaft lining rupture disasters in deep soil layers, and single-layer shaft lining technology with minimal leakage in deep water-rich rock layers, etc. Regarding the evolution of FSLT in China post-2002, the paper summarizes advancements in freezing shaft lining materials, introduces developments in cross-sectional and longitudinal freezing shaft lining structures, and generalizes new understandings regarding initial horizontal water and soil pressure in soil layers, water pressure borne by inner shaft linings, freezing pressure, and hydraulic loads induced by pore water in water-rich rock layers, as well as vertical additional forces. It briefly describes the mechanical model of shaft lining, the mechanical characteristics of high radial bearing capacity shaft lining and inner axially compressible shaft lining, the design theories for the thickness of both inner and outer shaft linings in double-layer composite shaft linings, the design theory for the thickness of single-layer freezing shaft linings in water-rich rock layers, and the design theory for inner axially compressible shaft lining. Moreover, it introduces the mechanisms and prevention technologies associated with thick shaft lining fracturing and leakage, corrosion damage and its prevention, information construction technology, as well as the construction technology for inner axially compressible shaft lining and low leakage single-layer shaft lining. In addressing the challenges that FSLT will encounter in 1 500 m ultra-deep soil layers and 3 000 m deep water-rich rock layers in China, this paper emphasizes the need for focused research on new mechanism and prevention technologies for shallow outer shaft lining rupture during frozen shaft excavation in deep soil layers, mechanical properties of ultra-deep soil, high-strength and high-performance building materials and components for shaft lining, ultra-high bearing capacity shaft lining structures and their mechanical properties, and design theories and construction technologies for ultra-deep frozen shaft lining.