Abstract:
The Pennsylvania Department of Transportation partnered with Gannett Fleming, Inc. to perform an emergency landslide repair of a 1-mile stretch of two-lane roadway in Ohioville Borough, Beaver County. This stretch of roadway had been failing along State Route 68 and the adjacent Norfolk Southern (NS) property into the Ohio river for more than 30 years. The subsurface conditions had been extensively investigated and instrumented by NS. On July 5, 2018, the landslide impacted the 4, 000 vpd roadway, including 12 percent truck traffic, causing a sudden shift in the eastbound lane. This failure prompted an immediate closure of 500 feet of roadway, restricting traffic to 1 alternating lane controlled by a temporary signal.
Investigations quickly concluded that the landslide occurred through a colluvial mass upwards of 50 feet in depth. This condition prompted the team to evaluate potential design solutions seldom considered in the generally steeply incised valleys with shallow, albeit sometimes very weak sedimentary bedrock lithologies of western Pennsylvania. In this instance, the designers broke out the deep soil mixed columns from the geotechnical toolkit, and in the cooperation with the Owner, were able to successfully apply this in-situ soil improvement technique to stabilize the area and restore the transportation corridor to a serviceable condition with a cost-efficient solution.