Freezing effect on shear strength of clayey soils

The design and construction of earth structures influenced seasonally by subzero temperatures requires the determination of mechanical properties of the construction materials under appropriate thermal conditions. Water saturated materials exhibit a zone of partially frozen soil at the frozen-unfrozen soil interface. To define the critical failure surface and governing shear strength in this zone, the effects of partial freezing on the mechanical behaviour as a freezing front advances, must be well understood. This paper presents a testing procedure for five clayey soils. It describes a series of laboratory direct shear tests to evaluate the effects of different freezing conditions at the shearing plane, on the shear strength of the thawing clayey soils. The major goal of this research was to understand these effects. From the results collected it was concluded that variations in the shear strength of frozen soils with time and temperature results primarily from variations in the ice cohesion and that the frictional resistance may be regarded as essentially constant. In practical terms, variations in the shear strength of frozen ground may be investigated in terms of their cohesion.