Process parameters of brineless ground freezing with a single freeze pipe

Abstract

Underground construction in cities is often carried out in complex hydrogeological conditions. The construction safety and protection of underground openings from groundwater influxes requires special methods to be used. One of such methods is artificial ground freezing. This method consists in enveloping a future underground opening with a system of vertical or inclined freeze pipes installed in drillholes. When it is necessary to construct a thin frozen wall, or to perform high-intensity freezing with a view to emergency response, it is effective to carry out brineless ground freezing using solid freezing agents. Wide-scale application of this method in underground construction is prevented by the lack of theoretical calculation techniques capable to determine the basic process parameters with regard to the properties of rock mass. This study analyzes theoretical relations which allow assessment of the frozen wall growth dynamics in artificial ground freezing with a single freeze pipe and prediction of the freezing agent amount sufficient for the frozen wall formation. The validity of the presented relations is proved by way of comparing the theoretical results with the finite element modeling performed for typical geological conditions of artificial ground freezing. The presented relations can be used to determine process parameters for creation of an impermeable frozen wall using a group of freeze pipes.