Mechanical Properties of Naturally Frozen Silty Soil for Seismic Design of Pile Foundations

Abstract

Frozen soils, especially seasonally frozen soils, have great impact on the seismic performance of bridge pile foundations. To account for its impact on pile foundations in the seismic analysis of bridge foundations, it is necessary to evaluate the mechanical properties of naturally frozen soil samples at a strain rate that is compatible to that induced in the frozen soil during a seismic event. This paper presents the mechanical properties obtained from testing of naturally frozen silty soils in Alaska. Uniaxial compression tests were conducted on naturally frozen soils including both seasonally frozen soils and permafrost obtained from Alaska. All tests were conducted at a constant deformation rate corresponding to a strain rate of 0.1%/s. Both horizontal and vertical specimens are tested under various temperatures below the freezing point. Testing results including soil characteristics and mechanical properties such as stress-strain curves, compressive strength, modulus of elasticity, and strains corresponding to the peak compressive strength and 50% of peak strength are presented. The impact of temperature and dry density on the mechanical properties is discussed.