Roadway Slope Repair
Erdman Anthony — PA Route 120
THE PROJECT
Over time, a 73-mile stretch of PA Route 120 has suffered slope failures at various locations that have mountainous terrain.
Erdman Anthony was selected to design the improvements as well as manage the geotechnical engineering provided by a subconsultant.
FEATURES/SOLUTIONS
Slope stabilization is being analyzed and remediated using a variety of methods, including soil nails and retaining walls. Subconsultant recommendations are being used to develop slope stabilization and structural, roadway, and drainage design as needed. The design at some locations is being expedited due to the emergency nature of the existing conditions.
The narrow corridor and terrain have led to innovative techniques, such as top-down construction involving soil nail installation from the existing roadway above the slope. Construction methods such as modifications to grout, soil nail socks, and modified soil nail installation patterns have been used in some areas to mitigate existing geologic conditions. Borehole cameras have also been used to identify existing soil conditions.
IMPACTS
The slope stability engineering and construction along the PA 120 corridor has helped remediate future roadway instability, including washouts during extreme weather events, and greatly enhanced safety for travelers through difficult mountain terrain. Design methods employed by the Erdman Anthony team, which have included design-build methodology, have provided safe traffic control during construction and shorter project durations.