The interaction between a flighted steel pipe pile and frozen sand

Abstract

Foundation construction in permafrost regions often make use of "thermopiles" or thermal piles to maintain the permafrost and to transfer load to the soil. Often "thermopiles" are constructed using shafts with continuous helical flighting attached to increase bearing capacity. The behaviour of these flights is essentially unknown as is the associated loss of shaft adfreeze during failure. An experimental study using a flighted instrumented segment pile in frozen sand was undertaken. The pile segment was loaded axially to near-failure. Load transferred from the pile segment to the surrounding soil consisted primary of two components; direct bearing by flighting and adfreeze/shaft friction. Flighting carried approximately 75% of the applied axial load, while adfreeze/shaft friction transferred approximately 18% of the load under specific test conditions. At large displacements, yielding at the flighting root resulted in the development of an ultimate axial pile capacity. In general, flighted piles develop significant (1080 kN/m) load transfer capacities.