Laboratory studies of near surface permafrost conditions in fine-grained soils from the Mackenzie valley, NWT

Abstract

Laboratory studies were conducted on fine-grained soils from the Mackenzie valley, N.W.T., Canada, to study the transient layer. Two laboratory models simulating repeated freeze-thaw cycles were placed in a walk-in freezer. Temperatures and pore water pressures were monitored along the soil columns during eleven freeze-thaw cycles. At the end of the testing program, soil moisture conditions and cryostructures were examined. Temperature and pore water pressure data were compared to computed results and the thaw consolidation theory, respectively. In both laboratory models, an ice-rich zone developed at the active layer and permafrost interface as a result of moisture migration to the freezing front. The high ice content zone was altered under extreme air temperature conditions. Distinct cryostructures were created after repeated freeze-thaw processes. The formation and shifting of the ice-rich zone provide useful information on moisture conditions and the cryostructures for further understanding the transient layer.