Abstract

Deep-seated landslides represent a persistent geohazard to transportation infrastructure in the Blue Ridge Province of western North Carolina. This study investigates the Dellwood and Ela deep-seated landslides, located along the Swannanoa Lineament, to determine the primary mechanisms driving their long-term movement.  The Swannanoa Lineament is an east-west-trending geological zone of fractures in western North Carolina.  The lineament is roughly 250 kilometers (155 miles) long and stretches from Fontana Lake in the west, through Canton and Asheville along the I-40 corridor, through the Swannanoa Gap (near Ridgecrest/Old Fort), and ends near Lake Hickory in the Piedmont.  Field mapping and structural analysis reveal that highly persistent bedrock fractures, oriented adversely to the hillslope gradient, facilitated slow-onset failure and continuous creep.  The Dellwood landside was found to be a wedge failure bound between the lineament fractures and foliation.  The Ela landslide has been identified as a location of constant shedding of blocks that are breaking along joints.  Ela joints strike northwest/southeast and dip generally northeast.  By correlating fracture sets with landslide boundaries, we demonstrate that these discontinuities serve as the primary failure planes, significantly increasing the risk to North Carolina roadways. Understanding these structural drivers is essential for developing predictive models and effective mitigation strategies for slow-moving mass wasting events in fractured crystalline rock. 

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