InfraVoid A HDPE Void Former: Cross River Tunnel Project Brisbane

Case Studies

// Case Studies • InfraVoid

InfraVoid A HDPE Void Former: Cross River Tunnel Project Brisbane

The Project

The Cross River Tunnel Project in Brisbane is a major infrastructure development aimed at enhancing the city's transport network by creating a new rail tunnel beneath the Brisbane River. This ambitious project included the construction of a new station at Albert Street, necessitating advanced engineering solutions to protect the tunnel linings and ensure long-term structural integrity. A critical component of this project was the use of InfraVoid, an innovative Void Former, designed to address the challenges of tunnel lining protection and drainage.

Challenges

Constructing a tunnel beneath a river presents unique geotechnical challenges, particularly in managing the pressures exerted by groundwater and soil movement. The tunnel's lining needed to be robust enough to withstand these pressures without succumbing to deformation or collapse. Additionally, the construction activities, including the use of Tunnel Boring Machines (TBM), introduced vibrations that could impact the structural integrity of the tunnel.

The project required a solution that could form a compressible void to absorb pressure changes and prevent the concrete lining from collapsing inward. It also needed to be lightweight, easy to install in confined underground spaces, and resistant to the harsh conditions of an underground environment.

// Our Solution

InfraVoid was selected for its superior performance as a compressible, waterproof composite geosynthetic void former. It consists of a cuspated HDPE sheet with a welded HDPE geomembrane. This innovative design allows InfraVoid to compress under pressure, protecting the tunnel lining from groundwater and soil movements, as well as TBM-induced vibrations.

Key benefits of InfraVoid include:

Effective Pressure Absorption: InfraVoid is engineered to compress when exposed to normal stresses, such as those greater than those associated with concrete placement. This feature prevents excessive loads from damaging the permanent tunnel lining by absorbing and redistributing the pressure.
Ease of Installation: The lightweight nature of InfraVoid allows for easy handling and installation using basic fasteners. This is particularly advantageous in underground environments where space and accessibility are limited. Its installation does not require specialized welding equipment or highly skilled labor, unlike some alternative products.
Enhanced Durability: The HDPE geomembrane layer of InfraVoid provides excellent resistance to water infiltration and chemical degradation, ensuring long-term durability in harsh underground conditions. This makes it a reliable solution for projects requiring robust and enduring protection.
Cost-Effectiveness: By preventing the need for extensive scaffolding and reducing the risk of installation errors common with polystyrene-based void formers, InfraVoid offers a more cost-effective solution. Its ease of installation also translates to shorter construction times and lower labor costs.

Project Implementation

At the Albert Street station site, InfraVoid was installed following tunneling activities, with the geomembrane layer facing inward. The installation process involved positioning the InfraVoid against the extrados of the tunnel lining and securing it with fasteners. Subsequently, a layer of shotcrete was applied over the geomembrane, further securing the void former in place.

The use of InfraVoid in the Cross River Tunnel Project demonstrated its efficacy in protecting the tunnel lining from external pressures and movements. The compressible nature of InfraVoid ensured that any ground or water pressure changes were absorbed, preventing structural damage to the tunnel.

Conclusion

InfraVoid proved to be an invaluable component in the Cross River Tunnel Project, providing a reliable, durable, and cost-effective solution for tunnel lining protection. Its innovative design and ease of installation helped overcome the significant geotechnical challenges posed by the project, ensuring the structural integrity of the tunnel and contributing to the successful completion of this critical infrastructure development in Brisbane.

// Project Gallery

Discover Our Work

Image for InfraVoid A HDPE Void Former: Cross River Tunnel Project Brisbane