The Huon Valley Council is situated south of Hobart—the southernmost local government council in Australia. Esperance Coast Road, Huon Valley, Tasmania, was showing several signs of deterioration along its length, including deformation, cracks and edge failure. To mitigate this, Huon Valley Council enlisted consultant Pitt and Sherry to undertake pavement investigations, focusing on the section between the Huon Highway and Police Point Road. Esperance Coast Road runs through a hilly area, with a high slope on one side and a valley on the other. High surface runoff and a lack of horizontal drainage caused the pavement to erode over time. Water accumulated in the pavement, which reduced the pavement layer’s structural capacity to support heavy traffic loads.
The consultant and asset owner, Huon Valley Council, contacted geosynthetics engineering firm and distributor Geofabrics to help with a solution to control the water ingress and improve drainage. The engineering firm recommended using the Presto GeoSystems GEOWEB 3D Soil Stabilization System to stabilize the base layer of the pavement, prevent degradation and provide drainage. The engineers worked closely with the Presto GeoSystems design team to develop a cost-effective solution for this problem, which council engineers accepted. Based on pavement investigation, a subgrade California Bearing Ration (CBR) of 2% was considered in the preliminary evaluation.
An engineering firm representative was on-site to provide installation assistance and support. The installers prepared the subgrade according to council specifications. A formation width of 25 feet (7.6 meters) was suitable to install one panel of 6-inch (150-mm) GEOWEB geocells in a transverse direction. The geocell panels connected with the patented ATRA Keys to provide positive associations between them.
One lane remained open to keep the traffic flowing while the project was underway. Half of the geocell panels were expanded and secured with 20-inch (500-mm) long pins. To create a horizontal drainage path through the geocell-stabilized base course, ¾ to 1¼-inch (20-mm to 30-mm) crushed aggregate was recommended and placed in the cells. Perforated geocells offer high-flow capacity through the panel without compromising the structural capacity of the pavement material. Once filled, a 20-ton truck was easily placed over the aggregate-infilled geocell panels without any deformation over the surface.
In total, 15,069 square feet (1,400 m2) of the system was installed and infilled with crushed aggregate. The cellular confinement technology improved the performance of the base layer, which also allowed the creation of a horizontal drainage layer without compromising the structural bearing capacity.
The council engineering team continues to monitor the pavement’s performance with the stabilized base layer and is pleased with how it is performing. Compared to conventional methods, a GEOWEB-stabilized layer allowed pavement thickness to be reduced by 50%, further removing the number of truck movements to construct the road.
GEOWEB geocells are the most advanced soil stabilization technology available
The GEOWEB geocell technology was developed by Presto GeoSystems and the U.S. Army Corps of Engineers to allow heavy vehicles to travel over soft ground. It is widely used for load support, erosion control, slope stabilization, retaining walls and high-velocity channels.
Through an interconnected honeycomb-like network, the 3D geocells confine and stabilize soils that would otherwise be unstable under loading. The cellular confinement system comes in collapsed, lightweight panels making them safe and easy to handle on project sites.
This case study first appeared on the Presto GeoSystems case studies website, www.prestogeo.com/case_studies.