Wattamolla Road in Woodhill NSW was affected by several prolonged and heavy rainfall events in early 2022, triggering slope instability of the site.
The resulting landslide had rendered the road impassable, and Shoalhaven City Council needed to temporarily remediate the road and restore access while a long-term solution was being engineered.
For this project, several options were available, including filling with geogrid and granular material, using a geosynthetic cellular confinement system to hold soil in place, or realigning the road to allow access for residents and emergency light vehicles.
These options would all allow short-term use of one lane of the landslide-affected area of Wattamolla Road. A permanent solution would require further investigation, analysis and detailed design to allow heavier traffic to pass through the damaged section.
To deliver a temporary fix, the cellular confinement technique was chosen as the most efficient and economically viable solution.
The Polyfabrics team worked with the contractor to supply over 1400m² of 200mm EROWeb® geocells, and over 700m² of geogrid for this project.
EROWeb® Geocell is a 3D expandable cellular confinement system made from HDPE. It is used to confine various infills and provide stability on slopes and channels when filled with locally sourced material. This offers a cost saving, especially in remote locations where require importation. Much more economical than building a permanent road structure, it allowed the contractor to deliver the repair quickly and efficiently.
This was installed over a layer of GG4040 Geogrid, providing stability and reinforcement to this remediation solution.
Along with additional drainage controls to prevent surface water flows and temporary barriers to restrict access to the outer edge of the road, this solution allowed the contractor to re-open the road quickly, providing critical access for local residents.
Just weeks after this project was completed, another heavy rain event occurred dumping 200mm+ of rainfall on the area without any damage to the EROWeb® installation.
For more information on the products used in this project, contact the team at Polyfabrics.