Frozen Soil Lateral Resistance for the Seismic Design of Highway Bridge Foundations. Final Report

摘要

Frozen soils, especially seasonally frozen soils, have a significant effect on the seismic performance of bridge pile foundations. To account for this effect, it is necessary to evaluate frozen soils mechanical properties. This report focuses on obtaining the mechanical properties of naturally frozen silty soils in Alaska. High-quality specimens of both permafrost and seasonally frozen soil were prepared by block sampling and machining following a procedure designed to minimize mechanical and thermal disturbances. Both horizontal and vertical specimens were prepared to investigate the effect of specimen orientation. Unconfined compression tests were performed at temperatures ranging from -0.7DG to -11.6 degrees C at a constant deformation rate that corresponds to a strain rate of about 0.1%/s. This strain rate is equivalent to that expected in the frozen soil during a design earthquake in Interior Alaska. Test results including soil characteristics and mechanical properties (stress-strain curves, compressive strength, yield strength, and modulus of elasticity) are presented and compared with data in the literature. The impact of temperature, dry density, water content, and specimen orientation on mechanical properties is discussed. These mechanical properties can be directly used to evaluate frozen soil lateral resistance in the analyses of laterally loaded pile foundations during seismic or other events in cold regions.