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The Effect of Confining Pressure and Water Content on Compressive Strength and Deformation of Ice‐Rich Silty Sand

The characteristics of ice‐rich frozen soils are important to engineering design in cold‐climate regions. Previous work has concentrated on uniaxial strength properties, and limited data exist on triaxial strength and deformation as a function of volumetric ice content and confining pressure. Triaxial compressive tests carried out on ice‐rich frozen silty sand indicated that the strength decreases to a minimum and then increases up to that of pure ice for a range of volumetric ice contents. However, the effect of confining pressure on the strength depends on the volumetric ice content itself. The strength was at a nearly constant minimum level when the volumetric ice content was between 48.2 and 65.1 per cent, dominated by the cohesion of the ice matrix. In contrast, at volumetric ice contents of > 27.2 to < 50.2 per cent and > 80.9 per cent, the strength increased with increasing confining pressure. The volumetric ice contents corresponding to maximum failure strain and minimum strength were 50.2 and 61.9 per cent, respectively. Thus, in this range an increase of about 10 per cent in volumetric ice content causes the failure strain to drop to the value for pure ice. The results indicate that there is a transition zone when the volumetric ice content is between 50.2 and 61.9 per cent that separates sample behaviour from that of frozen soil to that of pure ice. Copyright © 2016 John Wiley & Sons, Ltd.