Chapter 20

Frost heave in freezing soils

Damage to roads and pavements in regions which experience prolonged freezing is essentially due to the process whereby ice lenses accumulate in the subsoil (the damage occurs in thawing, when melting leads to ground collapse), and this accumulation is part of the phenomenon called frost heave, as the suction of water towards the freezing front to produce the lenses also causes the ground surface to heave. Although studied since the 1930s, the mechanism of frost heave is still controversial. This chapter considers one model, that due to Miller, and shows how it can be reduced to a much simpler form, essentially a quasi-static generalised Stefan problem with a complicated interfacial (Stefan-type) condition. In one dimension, the model can even be solved explicitly.

In his thesis, Chris Noon shows how these procedures can be applied to more complicated models, including compressibility and saline soils, and a similar reduction. He also shows that the model is susceptible to a spatial instability, and this may explain the formation of earth hummocks, which are prevalent in places such as Iceland (and there is a nice photo of them by Bill Krantz opposite page 370). Some of this latter work has been published (Fowler and Noon 1997a,b), albeit succinctly.