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|Title:||Measurement of frost heave forces on H-piles and pipe piles|
|Authors:||United States. Federal Highway Administration.|
Alaska. Dept. of Transportation and Public Facilities.
Johnson, Jerome B.
Buska, James S.
|Publisher:||Cold Regions Research and Engineering Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||CRREL report ; 88-21.|
Abstract: The magnitude and variation of forces and shear stresses, caused by frost heaving in Fairbanks silt and the adfreeze effects of a surface ice layer and a gravel layer, were determined as a function of depth by using electric strain gauges along the upper 2.75 m of a pipe pile, 30.5-cm I.D. x 0.95-cm wall, and an H-pile, 25.4-cm web x 85 kg/lineal m. The peak frost heaving forces on the H-pile for three consecutive winter seasons (1982-1985) were 752, 790 and 802 kN, respectively. Peak frost heaving forces on the pipe pile of 1118 and 1115 kN were determined only for the second and third winter seasons. Maximum average shear stresses acting on the H-pile were 256, 348 and 308 kPa during the three winter seasons. Maximum average shear stresses acting on the pipe pile were 627 and 972 kPa for the second 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 15 to 20% of the peak forces measured on the piles. A 0.6-m-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. Maximum heaving forces and shear stresses occurred during periods of maximum cold and soil surface heave magnitude. These were not related to the depth of frost penetration for most of the winter since frost was present at all depths extending to the permafrost table. Soil surface displacements of 2 to 7 cm were measured at the experiment site during the study. The important mechanisms that determine the magnitude of uplift heave forces are 1) soil heaving as the driving force, and 2) soil temperature, which controls the unfrozen water content, mechanical properties of the soil and the area of influence of heaving pressure.
|Appears in Collections:||CRREL Report|