Direct by Design Delegates from across the world attended the recent Ground Freezing Symposium in London
11th INTERNATIONAL SYMPOSIUM ON GROUND FREEZING REPORT
….. the answer is – freeze it Shani Wallis, TunnelTalk
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he application of ground freezing has been a vital geotechnical support technique for mining and underground construction for many decades, but not for 17 years, since 2006 in Maine, USA, has there been an international forum for sharing the knowledge, expertise and experience of the design and construction processes for working with ground freezing and frozen ground. That changed last week, in October 2023, when academics, designers, project clients, and specialist contractors, gathered for the 11th International Symposium on Ground Freezing in London to update developments in the state-of-the-art construction associated with frozen soils. Through recent years, developments in the site investigation requirements, the testing of frozen soils to understand their behaviour, and the technology of brine and liquid nitrogen freeze plants, have advanced significantly and the proceedings of the three-day symposium cover all these aspects and in thorough detail.
Oct 2023 solution. Successful passage of tunnels under rivers, for excavation of cross passages in permeable soils, and for sinking shafts through waterbearing ground, often to great depths, have all proven the value of this fascinating geotechnical support technique that occurs naturally in permafrost zones and the cold regions of the world. Among the 56 papers presented in the three-day programme, Alan Auld, Co-chair of the event with Joe Sopko of the USA, addressed the thorny debate between grouting and freezing and cautioned those making decisions about the most effective method of controlling groundwater to not dismiss the ground freezing option without careful in-depth consideration, particularly with respect to the risks involved should grouting fail to achieve the support and water control objectives. The laboratory testing of frozen ground samples has advanced considerably over recent years
As a starting point, decisions concerning whether to freeze or use grouting to control water ingress into underground excavations opens the discussion. In initial studies ground freezing is the more expensive option and many clients choose the lesser expensive grouting option hoping that grouting will provide the solution they seek. The unhappy reality is that when grouting fails, as it often does, the only remaining solution is to apply artificial ground freezing to rescue the situation and accept the much higher turnout cost of the failed grouting cycles, plus the time and cost of applying ground freezing. The more astute decision, with less risk exposure, would have been to adopt ground freezing from the start, and in recent times, several projects have adopted ground freezing over grouting as the best value 1
