Development of Bearing Capacity of Fine Grained Permafrost Deposits in Western Greenland Urban Areas Subject to Soil Temperature Changes

摘要

The bearing capacity of frozen soils is high, compared to non-frozen soils of same composition. Projected climatic warming in the Arctic will increase the soil temperature, thus affecting the bearing capacity and the deformation properties. Western Greenland temperatures are projected to increase by 2-3 °C during the 21st century. This paper presents a relation between undrained shear strength and temperature based on a series triaxial tests of fine-grained permafrost in the interval from -3 °C to -1 °C. Moderately ice-rich permafrost and excess ice free refrozen active-layer were retrieved from the Western Greenland towns of Sisimiut and Ilulissat respectively. Tests reveal undrained shear strengths ranging from 409 kPa to 940 kPa, where low temperatures and low excess ice content yield higher strengths. Normalized strengths are used for establishing a trend for the strength decrease with increasing temperature. Both excess ice free and moderately ice-rich samples show a strength decrease of 21 %/°C from -3 °C to -1 °C. Other authors' data suggest the same trend for moderately ice-rich samples, whereas it is suggested that further studies are conducted to validate the trend for excess ice free samples. Unfrozen water contents are seen to be directly inversely proportional to the undrained shear strength when both are normalized, which may reduce costs for establishing reliable soil strength parameters. It is suggested that a relation to deformation parameters are investigated as well. The established trends could provide a valuable tool for foundation design in fine-grained permafrost areas.