Frost Heave Forces on H and Pipe Piles Embedded in Fairbanks Silt: Fid-Bau Portal

Frost Heave Forces on H and Pipe Piles Embedded in Fairbanks Silt

J. B. Johnson / J. S. Buska

The magnitude and variation of forces and shear stresses, caused by frost heaving of a Fairbanks silt active layer, were determined using computerized data logging of electric strain gauges placed at one foot intervals of depth on both a 12-inch diameter pipe pile, and an H pile. Studies continued for three consecutive winter seasons (1982-1985). The peak frost heaving forces on the H pile during the three winters, were respectively 752, 790, and 802 kN (169, 178, and 180 kips). Peak frost heaving forces on the pipe pile of 1118 and 1115 kN (251 and 251 kips) were determined only for the second and third winter seasons. Maximum average shear stresses acting on the pipe pile were 627 and 972 kPa (91 and 141 psi) for the second and third winter seasons. Ice collars were placed around the tops of both piles during the first and third winter seasons. Ice collars were placed around the tops of both piles during the first and third winter seasons to measure the adfreeze effects of a surface ice layer. The ice layer may have contributed as much as 20% of the peak forces measured on the piles. A 0.6-m (2.0 ft.) thick gravel layer replaced the soil around the tops of both piles for the second and third winter seasons to measure the adfreeze effects of a gravel backfill. The gravel layer on the H pile may have contributed about 35% of the peak forces measured. The forces for both piles generally increased following a decrease in air temperature and decrease or relaxed following a rise in air temperatures. Changes in forces acting on the piles usually lagged behind corresponding air temperature changes by 1 to 8 days. Maximum heaving forces and shear stresses occurred during periods of maximum cold and maximum soil surface heave.