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 pop 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 forst was present at all depths extending to the permafrost table. (mjm).

A simple momentum model, assuming that snow compacts to its final density at negligible stress, is used to estimate shock wave attenuation in snow. Four shock loading situations are examined: a one-dimensional pressure impulse of finite duration and instantaneously applied pressure impulses for one-dimensional, cylindrical and spherical shock geometries. Calculations show that while a finite duration impulse is being applied, the shock pressure in snow is determined by the impulse pressure-time profile. After the pressure impulse has been applied, the one-dimensional shock pressure decay is the same as for an instantaneously applied pressure impulse and is proportional to the inverse square of the shock propagation distance. Hence, finite-duration pressure impulses delay the onset of shock attenuation in snow. This can result in more pressure attenuation near a shock source, where the positive phase duration of the shock is short, compared to shock waves farther from a source. Cylindrical waves have a maximum decay that is proportional to the inverse of the propagation radius to the fourth power (1/R(to the fourth power), and spherical waves have a maximum decay that is proportional to 1/R (to the sixth power). Amplitude decay for cylindrical and spherical shock waves can vary from (R-40)-2, when (R-R0)“R0 (where R0 is the interior radius over which a pressure impulse per unit area is applied), to their maximum decay.