Rising Above the Floodplain: Geosynthetics for a New Campus in Northern Rivers
The Project
Severe flooding in 2022 left a campus in the Northern Rivers region of NSW badly damaged. Rather than rebuild on the same site, the decision was made to completely relocate the campus to higher ground nearby. The construction scope included new teaching facilities, sporting fields, roadways and car parking, with the new campus planned to open during 2027.
Global Synthetics became involved early in the project, working with the geotechnical engineer and later supporting the civil subcontractor with geosynthetic and drainage products for a number of applications across the site.
The Challenge
The lower areas of the development presented several geotechnical challenges.
Soft and potentially expansive subgrade conditions beneath the lower car park and road pavements required a solution that could improve pavement performance and provide a reliable working platform during construction.
Although the new site sits on higher ground than the previous campus, flooding remained an important design consideration. The lower sporting fields and pavement areas could still be inundated during significant flood events, creating the potential for rapid drawdown as floodwaters retreat. This had to be factored into the stability of the slopes between the lower flood-prone areas and the elevated sections of the campus.
Effective subsoil drainage and filtration were also important to control groundwater and protect both pavement and earthwork materials.
The Solution
From the early design stages, Global Synthetics worked with the project geotechnical engineer to develop a combined solution covering slope reinforcement, pavement support, separation, filtration and subsoil drainage.
For the reinforced slopes, ACEGrid® PET, a high-tenacity polyester geogrid was selected to provide structural reinforcement. The availability of long-term design strength values allowed the engineer to incorporate the geogrid into the slope stability analysis and design the reinforced soil structure for its required design life, including consideration of potential rapid drawdown conditions.
For the lower car park and road pavements, Naue Combigrid® Geocomposite 40/40 was used in conjunction with the rock blanket over the soft subgrade. Combigrid® combines geogrid reinforcement with an integral nonwoven geotextile, providing reinforcement, separation and filtration in a single product. The rock blanket was wrapped top and bottom with the geocomposite, helping to maintain separation from the underlying expansive soils, improve aggregate confinement and provide a more stable working platform.
This gave the geotechnical engineer greater confidence in the performance of the rock blanket during pavement construction and helped reduce the risk of movement at subbase level.
Geofirma® Nonwoven Geotextile was also supplied for separation and filtration, particularly for wrapping drainage aggregates to help prevent migration of surrounding soil fines into the drainage system.
ProPipe Ag Pipe was incorporated into the subsoil drainage system to collect and convey groundwater and infiltrated water away from the pavements and earthworks.
The Result
The project demonstrates how a combination of geosynthetic reinforcement, separation, filtration and drainage can be used to address several different geotechnical issues within one development. Early involvement with the geotechnical engineer allowed Global Synthetics products to be considered as part of the engineered solution, rather than simply being supplied during construction. The result is a set of practical, integrated solutions for a development where long-term flood resilience is a key consideration.
Working on a site with flood, drawdown or drainage challenges? Contact Global Synthetics today to talk through geosynthetic solutions for your site.
