Geophysical Investigation and InSAR Mapping of Permafrost and Ground Movement at the Iqaluit Airport

The history of Iqaluit airport has been punctuated with noticeable settlement and frost cracking problems affecting the asphalt and the embankments. In order to characterize the permafrost conditions on which the performance of the engineering infrastructure depends, field campaigns were conducted and combined with remote sensing data. Electrical resistivity imaging (ERI) and ground penetrating radar (GPR) surveys were used to support surface observations made in the field and from air photos and provide extended spatial and vertical knowledge. The interferometric synthetic aperture radar (InSAR) mapping provided short term ground surface movement information. Interpretation from the GPR profile suggests the presence of ice wedges below the embankment that are associated with some of the settlement and frost cracking problems affecting the runway. Based on the geophysical interpretation, the thawing front, around a depth of 3 m, has reached the natural ground, and therefore, settlement due to melting ice wedges will probably continue. ERI also revealed a large-scale conductive anomaly at a depth of approximately 6 m below the asphalted surface of the runway and this feature might eventually lead to settlement problems. Within this area, the InSAR map showed greater downward ground surface movement over the course of one summer than the surrounding areas, with values around 4.5 and 6.6 cm. In general and at the scale of the InSAR data, the runway embankment shoulders appear quite stable. Although the InSAR data provided a good correlation with the terrain units, the ground truth measurements have shown slightly higher values of downward movement.