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