IMPROVED THERMAL COMPUTATIONS FOR ARTIFICIALLY FROZEN SHAFT EXCAVATIONS

Artificial ground freezing (AGF) techniques are widely used by civil a nd mining engineers to assist in the construction of shafts, tunnels, and other structures. The ground is frozen by a coolant circulated thr ough pipes inserted in the ground in order to create a cofferdam that will exclude ground water and provide structural support. Formulas by Sanger and Sayles are often used to estimate the growth of the freeze. The theoretical basis of these formulas are critically examined and a n alternative method of computing the extent of the frozen ground is g iven. The alternative method is based on some of the ideas of Sanger a nd Sayles and requires the numerical solution of one diffusion equatio n over a finite interval. Numerical results are presented using typica l data for granular soils with several different dry densities and wat er contents.