FILL SLOPE REPAIR USING SOIL BIOENGINEERING SYSTEMS

Abstract

Soil bioengineering is an applied science combining mechanical, biological, and ecological concepts to construct living structures for erosion, sediment, and flood control. Plant parts are used as the major structural components to reinforce the soil mantle. The live plants or cuttings may be used in conjunction with inert structural members such as wood, stone, or synthetic materials. This article describes a demonstration project to repair a fill slide on North Carolina 126, using soil bioengineering technology. The demonstration site was an 870-ft long fill slope that generally runs east-west and has a southern exposure. The embankment has a maximum height of 60 ft with a slope face ranging from 100 to 200 ft long. This fill section was constructed in 1980-81 with the slope varying from 1.5:1 to 2:1. The slope began to fail and erode shortly after construction and was repaired several times using conventional treatments. When the decision was made to repair the slope with soil bioengineering systems (December 1985), face sliding and erosion had started to undermine the guard rail posts at several locations and encroach on the pavement structure. Systems utilized included live staking, brushlayering, live fascine, and live cribwall. The analysis to determine the proper system to use in a given situation was critical, as was the proper installation of the systems.