Waterproofing in underground environments is often underestimated, particularly when it comes to resisting groundwater pressure and long-term system performance. Getting the fundamentals right early is critical to avoiding failure, rework, and costly remediation.
Based on decades of experience supporting complex infrastructure projects, Bluey has outlined key considerations to help ensure successful tunnel waterproofing outcomes.
1. Select the Right Membrane Type and Thickness
Membrane selection should be based on project conditions, groundwater pressure, and structural requirements. Not all membranes perform the same. Bluey offers both PVC and VLDPE systems, supported by international standards and practical experience, to ensure the right solution is specified from the outset.
2. Consider Ground Movement after Lining
Ground squeeze following concrete placement can place significant stress on the membrane system. Selecting a membrane with appropriate mechanical properties is essential. Bluey’s systems are tested to provide reliable performance under these conditions, with engineering support available to guide selection.
3. Use Engineered Solutions for Cross Passage Terminations
Terminating membranes to TBM segments has historically been a high-risk detail. Engineered compression gasket systems provide a reliable method for achieving watertight terminations and are now widely adopted across major tunnelling projects.
4. Specify Fixings That Maintain Membrane Integrity
Fixings through the membrane are often required for reinforcement, formwork, and services. These must be designed to maintain a watertight seal regardless of applied load, ensuring the integrity of the waterproofing system is not compromised.
5. Seal Uplift Piles Effectively
Terminating membranes around pile perimeters alone is not sufficient. Water can track through cracks and voids within the pile head. Engineered capping systems are required to provide a complete seal and prevent water ingress under pressure.
6. Use Appropriate Termination Methods for Diaphragm Walls
High-pressure terminations to diaphragm walls and sheet piles require engineered solutions. Adhesives or liquid membranes alone are not sufficient and are a common source of failure if not properly detailed.
7. Manage Groundwater Pressure During Installation
Groundwater pressure must be controlled behind the membrane prior to and during concrete placement. Failure to relieve pressure can result in membrane damage during the pour.
8. Install the Membrane with Correct Slack
Membrane installation requires a careful balance. Insufficient slack can lead to tension and tearing during concrete placement, while excessive slack can create folds and weak points. Proper quilting is essential.
9. Use Roundels Designed to Protect the Membrane
Plastic roundels are designed so that the weld will fail before the membrane is damaged under load. This protects the system during concrete placement and reduces the risk of tearing.
10. Complete Secondary Grouting to Eliminate Voids
Void formation is common in crowns and high points following concrete placement. These must be addressed through second-stage grouting using pre-installed injection points to ensure full support and waterproofing continuity.
Selecting the right membrane system is only one part of achieving a successful waterproofing outcome. Detailing, installation, and pressure management all play a critical role. Getting these elements right the first time reduces risk, improves performance, and avoids costly rectification. Bluey works alongside project teams to provide the engineering input, systems, and onsite support needed to deliver reliable waterproofing across complex underground environments.
