Predicting soil freezing depth for trafficability

In northern countries, soil frost supports vehicle movement on unpaved surfaces and roads and does not have a serious impact on soil properties, whereas unfrozen areas make trafficking difficult or impossible. Such areas include permanently wet soils (Gleysols) of various textures, and peat soils (Histosols), bogs and high moors. These types of unfrozen soils can only support vehicles with low contact pressures. The soil bearing capacity – the ability of a soil to support vehicle movement – changes with freezing conditions and can be 5–10 times higher than that of unfrozen soil [1]. On Histosols it is estimated that a 20–30 cm frozen layer is necessary to ensure safe driving and to retain the soil properties [2]. The higher the moisture content of the soil during freezing, the more similar it is to ice, which will subsequently raise the soil bearing capacity. The bearing capacity can vary from 1000 to 2000 kPa depending on the depth of the frozen layer, the density of the soil, and the properties of the vehicle [3]. For example, in the case of a 60 ton tracked tank, the ice depth should be at least one meter, but in the case of a 26 ton armoured wheeled vehicle the ice depth need only be approximately 70 cm.