Measuring the Impact of Landslide on Transportation Infrastructure to Improve Mobility and Safety

Abstract

Frozen debris lobes (FDLs) are landslides in permafrost, many located along the Dalton Highway corridor, Brooks Range, Alaska. The closest to the highway, FDL-A has demonstrated a steadily increasing rate of movement over the last several decades. Recognizing the risk, in 2018 the Alaska Department of Transportation and Public Facilities (ADOT&PF) realigned the Dalton Highway about 122 m downslope. While not a permanent solution, the realignment provided additional time for ADOT&PF to develop mitigation techniques to apply to FDLs. As part of this project, we installed subsurface geomechanical instrumentation to measure temperature and water pressure as FDL-A overrides the installation locations. We recommend continued monitoring of these installations. We successfully tested a backpack-mounted LiDAR technique, which produced high resolution (i.e., 0.1-m) digital elevation models for the FDL-A toe area. This technique allowed change detection and analysis, including volume change calculations. As of August 2, 2019, FDL-A was 17.3 m and 127.8 m from the old and new Dalton Highway embankments, respectively. Its rate of motion has transitioned from a linearly increasing rate to one that is exponential. Based on the 2019 rate, we predict that FDL-A will impact the old Dalton Highway embankment by 2021, and the new Dalton Highway by 2032. The imminent collision of FDL-A with the old embankment represents a unique opportunity to observe a landslide impacting infrastructure in a safe and controlled way and on a predictable schedule. Therefore, we recommend a Phase II portion of this research to measure the deformation of the embankment and subsurface; measure earth pressure during collision; and document the collision through geomechanical instrumentation, repeat LiDAR scans, and repeat photography.