Artificial ground freezing as a construction method for underground spaces in densely built up areas

Abstract

The study looked in to de possibilities to construct underground spaces with temporary artificial ground freezing as a construction method. To determine whether soil freezing is a viable option for underground construction in densely built up areas a case study has been performed for the North-South Line in Amsterdam. With the help of current developments found in the field of artificial ground freezing four different options of constructing a station were developed and compared. The most suitable of these options was modelled in Plaxis. To obtain the correct input parameters the processes occurring as a result of a freeze-thaw cycle were studied. Most important processes are the creep behaviour of the frozen soil, heave as a result of formation of ice lenses in low permeable soils and changing soil parameters due to the freeze-thaw cycle. It was concluded that an alternative design for one of the stations of the North-South Line using artificial freezing would be technically feasible. Also the financial aspects of the design were evaluated. Although the freeze design is more expansive then the currently executed design, the freeze design can compete. Costs are not two or three times as much with respect to conventional techniques as is often thought. In complex situations therefore ground freezing is a technique which should be taken in to account!