Artificial ground freezing (AGF) is a highly effective geotechnical process commonly used to stabilise water-bearing low-strength soils, provide temporary ground support, and control water ingress through fractured or faulted rocks and aquifers. It has successfully been used to stabilise excavations up to 64 m in diameter and shafts to depths of over 600 m. Compared with other geotechnical processes used to stabilise ground, AGF is unrestricted by soil grain size and can therefore accommodate the full range of soil and rock types. The process is transient and once the source of chilling is removed the ground and ground water conditions return to normal without contamination. The only limitation is that each stratum to be frozen must have adequate moisture, typically in excess of 5%.The paper describes the methods used to artificially freeze water-bearing ground in both shaft sinking and tunnelling, and stresses the importance of a comprehensive project specific Ground Investigation to determine both ground and ground water conditions, and allow engineering based decisions to be taken as to whether or not AGF would be advantageous. Design issues are briefly discussed together with the laboratory program essential to establish the mechanical and thermal properties of the proposed freezing horizons. A number of freeze examples have been chosen to illustrate well established principles applied to shaft and tunnel freezing. The paper concludes with a statement of the effectiveness and versatility of the technique of AGF.
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