The $10.3-million (£7.75-million) project from Crediton Industrial Link Road to the A377 in Devon, U.K., comprised a 760-meter single-lane road from Wellpark roundabout on the A377 into the Lords Meadow Industrial Estate. The link road forms a key part of Mid Devon District Council’s Air Quality Action Plan. It also was designed to reduce congestion and to support economic development. The approved Hillside route required 100,000 cu meters of material to be excavated, creating a steep-cut slope that would require extensive embankment stabilization.
The Solution
The Geoweb 3D soil stabilization system was selected to steady the erosion-prone embankment. Through confinement of infill materials in its deep, interconnected cells, the 3D system provides protection to the upper slope layer not provided by 2D planar “cover only” systems (e.g. erosion control blankets and turf reinforcement mats). The system resists sliding and prevents severe erosion caused by storm water runoff and sheet flow. The steep angle of the cut slope meant that the Geoweb system with a tendon anchorage system was suited to provide safe, secure stabilization of the infill over the slope face.
To assure complete system stability, ATRA tendon clips—load-transfer devices that relocate slope gravity forces from the Geoweb cell walls to the tendons—were utilized with high-strength tendons installed per design. The ATRA tendon clip device engages securely with the Geoweb cell wall for twice the pull-through strength than other load-transfer devices. A looped tie-off assures that tendons stay bound to the device.
Installation of the System
Once the 48,500 sq ft (4,500 sq meters) of Geoweb panels with the integrated tendon anchoring system were securely positioned on the slope, infilling commenced using onsite material. Infill was performed from the crest of the slope to the toe in accordance with Presto Geosystems’ installation guide. Controlled overfilling of cells was required to allow for consolidation and compaction of the infill.
The Geoweb material consists of textured, perforated cell walls that provide optimum interlock between cell walls and infill materials while significantly improving lateral drainage. This was an important factor in considering this solution for this particular site due to the positioning of the cutting and potential water flow issues.
Greening of the Embankments
Months after installation, the embankment is green and rich with vegetation. The vegetation was performed in accordance with the environmental statement prepared for Devon County Council by Jacobs Eng.
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