METHOD AND APPARATUS FOR ARTIFICIAL GROUND FREEZING

摘要

A ground freezing method and system which circulates refrigerated heat transfer fluid through freeze pipes in the ground at a low temperature of at least -52.degree.C (-62.degree.F) to minimize drilling for the freeze pipe installation. The heat transfer flu id is preferably aqua ammonia (ammonium hydroxide) because of its beneficial characteristics in th is application. The circulating heat transfer fluid is preferably cooled by a refrigeration system that includes low and high stage cycles arranged in a cascade relationship and using ammon ia or another refrigerant in the high stage refrigeration system and carbon dioxide as the refrigerant in the low stage refrigeration system.