Western Wake Expressway (Triangle Expwy SR540)
An existing slope along the northbound lane of the new Triangle Expressway had failed.
The slope was located along the base of a sound wall structure and previous attempts to re-grade the slope resulted in failures. The soil conditions consist of an upper zone of unstable disturbed soil over stable soil or soft rock.
GeoStructures installed Slope Reinforcement Technology (SRT) elements throughout the failure area of the slope. The piles were placed at 4 ft intervals parallel to the slope and at 7 ft intervals in the up-slope direction. The system was designed utilizing “Slide” slope stability modeling software based on an improved safety factor of 1.5 after installation of the SRT elements. No subsequent movement of the slope has been observed.
The SRT elements mobilize the strength of the soil through arching and transmit slide forces to the underlying stiffer soil. The downslope force on each Plate Pile is resisted by the bending strength of the Plate Pile shaft in combination with the passive resistance of the soil behind the plate.
North Carolina Department of Transportation