Mechanical Properties of Naturally Frozen Ice-Rich Silty Soils

Frozen soils, especially seasonally frozen soil, have great impact on the seismic performance of bridge pile foundations. To account for its impact on pile foundations during seismic events, it is necessary to evaluate the mechanical properties of naturally frozen soil samples. This paper focuses on the mechanical properties of naturally frozen silty soil in Alaska. High-quality specimens of both permafrost and seasonally frozen soil were prepared by block sampling and machining. Both horizontal and vertical specimens were prepared to investigate the effect of specimen orientation. Unconfined compression tests were performed at temperatures ranging from −0.7°C to −11.6°C at a constant deformation rate corresponding to a strain rate of about 0.1 %/s, which is consistent to the strain level expected in the frozen soil during a design earthquake in interior Alaska. Testing results including soil characteristics and mechanical properties such as stress–strain curves, compressive strength, yield strength, and modulus of elasticity are presented. The impact of temperature, dry density, water content, and specimen orientation on the mechanical properties is discussed.