Refraction Microtremor Characterization of a Landslide SR 14, Cedar Canyon, Utah

摘要

In October 2011, a landslide estimated to be about 520 meters wide, 300 meters long and 40 to 45 meters thick destroyed portions of Utah State Route 14 about 8 miles east of Cedar City, Utah. Reconstruction and reopening the highway was a very high priority for the Utah Department of Transportation (UDOT); knowledge of the failure plane depth and geometry was critical to mitigation and reconstruction. Over a two-day period amongst harsh winter field conditions in December 2011, the authors completed eight, 70-meter long surface Refraction Microtremor (ReMi) seismic surveys to develop two profiles perpendicular to the roadway to assist in identifying depth to competent material. Ambient surface wave noise from contractor access road pioneering served as the seismic source. Interpreted seismic velocities from the shear wave profiles were used to estimate geo-material mass density and unconfined compressive strength. These correlations were useful in assessing the loose or otherwise shattered rock and soil slide mass to aid in identifying a competent material surface beneath the slide. Estimated ReMi shear wave depths of investigation ranged from about 30 to 60 meters. Two exploratory borings with inclinometer installations were completed by UDOT through the slide to monitor further movement.