P-Y Approach for Laterally Loaded Piles in Frozen Silt

Frozen soils, including seasonally frozen soils and perennially frozen ground, or permafrost, exist extensively in Alaska and other cold regions. During past earthquakes, extensive damages were observed in pile foundations, and frozen ground appears to be the direct cause of at least some of those damages. This paper analyzes frozen soil lateral resistance and its effects on pile foundations during earthquakes based on the testing results on reinforced concrete-filled steel-pipe piles embedded in deep seasonally frozen silts under large deflection and recommends an analysis tool for seismic design practices. Pile performance data measured in the testincluding bending moment and deflectionwere used to back-calculate the p-y values for the top half-meter of frozen silt. A p-y curve for frozen silt is proposed based on the experimental data. Results from modeling the test pile using the proposed p-y curve agree well with the test results. The proposed p-y curve was further validated by independent field test data. It is concluded that the proposed p-y curve is capable of modeling both seasonally frozen and perennially frozen silts in frozen soil-pile interaction analyses during short-term lateral loading. Recommendations are provided on how to select soil parameters for constructing frozen-silt p-y curves. (C) 2017 American Society of Civil Engineers.