Discover how certified fire protection panels like Panacor Panel Rock prevent concrete failure in tunnel fires and learn about fire protection standards with Kubri Engineered Solutions.

Tunnel fires are unforgiving. A fire protection system in a tunnel either works or it doesn’t—failure can lead to severe structural damage or even loss of life.
Passive fire panels are one of the most effective solutions. They are rigorously tested to withstand extreme hydrocarbon fires and prevent concrete spalling. Designed for durability, these panels also meet strict installation and regulatory standards.

As their exclusive distributor in Australia, Kubri Engineered Solutions supplies these high-performance panels from Panacor, a European manufacturer of certified fire protection panels for tunnels. In this blog, we’ll explain how these structures work and why they are crucial to modern tunnel design.

Understanding Fire Risks in Tunnels

Tunnels introduce a set of fire risks that differ significantly from above-ground structures in their severity and behavior: 

1. Extreme Heat and Confinement

Tunnel fires can heat up extremely fast. Temperatures may reach 1200°C within 10 minutes and even 1300°C in hydrocarbon fires. In the confined space of a tunnel, heat cannot escape, increasing the risk of structural damage and collapse.

2. Toxic Smoke and Low Visibility

Smoke and toxic gases can accumulate quickly in tunnel fires. With inadequate ventilation underground, visibility is reduced, evacuation is compromised, and emergency responders are at risk.

3. High Pressure and Steam Effects

Tunnels also endure dynamic pressure changes caused by high-speed traffic. In combination with confined steam generation, these create internal forces (forces that can exceed 5000 Pa in some designs) that challenge the structural stability of critical underground infrastructures.

What Happens to Structural Concrete in Tunnel Fires?

1. Explosive Spalling in the First 30 Minutes

Rapidly heated concrete traps moisture in its pores, which turns to steam. As the steam cannot escape, internal pressure builds, causing explosive spalling—the violent ejection of surface layers. This not only weakens the concrete but also exposes the steel reinforcement to direct flames.

2. Rapid Strength Loss of Reinforced Concrete

Concrete begins to lose its compressive strength at around 300°C, and the steel reinforcement loses its yield strength as temperatures approach 550-600°C. In a tunnel fire, these thresholds can be exceeded in minutes. Without adequate thermal shielding, beams and linings may no longer be able to support their intended loads.

3. Progressive Collapse Risk

Structural degradation often follows a cascading path. Spalling exposes the steel, which weakens, and subsequently, the load-bearing capacity drops. As the heat continues to rise, this cycle accelerates, increasing the likelihood of partial or full collapse. This endangers lives and complicates rescue operations.

Fire Protection Panels & Their Role in Preserving Tunnel Integrity

Fire protection panels are passive systems engineered to delay the thermal effects of fires on structural concrete. In tunnel infrastructure, they serve three main purposes:

1. Extend the structure’s fire endurance.
2. Prevent material failure.
3. Buy time for evacuation and emergency response.

How Do Fire Protection Panels Operate?

These panels form a thermal barrier that insulates the tunnel lining from direct flame contact. By reducing the rate of heat transfer into the concrete, they maintain the substrate temperature below the critical thresholds at which spalling and rebar deformation begin. Most high-performance panels can lower surface temperatures by hundreds of degrees during a fire event.

Mechanical Fixing vs. Sprayed Coatings

Unlike sprayed-on protection systems, mechanically fixed panels are not affected by substrate adhesion loss, humidity, or vibration. This makes them especially suitable for tunnel conditions, where long spans, curved surfaces, and frequent pressure fluctuations are common. Panels retain their protective properties even under dynamic loading and environmental cycling.

Passive Systems Vs. Active Systems in Critical Phases

Passive systems work automatically when exposed to heat. They need no sensors, electricity, or maintenance to function in an emergency. This is crucial in tunnels, where active systems—like sprinklers or smoke suppression—can fail due to power loss or mechanical issues.

Australian Fire Compliance Standards for Tunnel Protection Systems

1. AS 4825:2011: Tunnel Fire Safety Design Framework

This standard outlines fire safety design principles for road, rail, and bus tunnels in Australia. Key requirements include:

• Integration of passive and active fire protection measures
• Strategies for structural fire resistance, ventilation, and evacuation
• Guidance on fire hazard assessment, redundancy, maintainability, and reliability
• Lifecycle documentation covering design, installation, commissioning, operation, and maintenance of fire systems

2. AS 1530.4:2014: Fire Resistance Testing of Construction Elements

This standard defines the method for validating performance under controlled exposure to fire. It addresses:

• Structural integrity and insulation evaluated against load-bearing ability
  
• Use of time-temperature curves aligned with ISO 834
• Testing of full-scale specimens (walls, panels, ceilings, etc.)

3. Lifecycle Compliance and Supplementary Standards

• Standards such as AS 1851 specify routine inspection and documentation processes for installed systems. 
• AFAC guidelines align tunnel system design with practical emergency response considerations

4. International Benchmark Standards

While Australian codes form the regulatory baseline, many systems are also tested to international standards as part of their performance validation:

• EN 1364‑1:2015 and UNE EN 1363‑2:2000 for hydrocarbon fire testing of wall elements
• RABT‑ZTV (Germany) and RWS (Netherlands) fire curves simulating severe tunnel fire conditions

5. What Compliance Requires in Practice

• Maintain concrete surface temperatures below 300 °C (RABT) or 380 °C (RWS) during the fire event.
• Keep reinforcement steel below critical thresholds (generally below 250 °C with minimum cover)
• Prevent or limit concrete spalling and structural deformation.
• Sustain mechanical stability without delamination or structural failure.
• Undergo inspections and condition audits as part of lifecycle assurance.

Panacor: Acoustic and Protective Solutions for Infrastructure

Panacor is an established European manufacturer specializing in advanced acoustic and structural protection systems. With decades of experience, the company delivers high-performance solutions in noise walls, wind barriers, fire protection panels, and enamel steel panels.

Panacor Panel Rock is engineered specifically for tunnels and other high-risk infrastructure, where both fire resistance and acoustic control are critical to performance. Unlike general-purpose fire protection materials, Panel Rock is designed and tested to meet the structural and thermal demands of enclosed transport systems.

1. Certified Fire Resistance Under Tunnel Conditions

Panel Rock has been tested under hydrocarbon fire curves, including RWS (Netherlands) and RABT-ZTV (Germany), withstanding temperatures of up to 1100°C for a minimum of two hours. The panel is certified to:

• EN 1364-1:2015 – Fire resistance of wall assemblies
• UNE EN 1363-2:2000 – Fire curve exposure testing

2. Dual Functionality: Acoustic and Thermal Control

Tunnel projects often require both fire protection and noise mitigation, particularly in densely populated urban environments. Panel Rock meets:

• EN ISO 354 – Sound absorption
• EN 1793-1 – Road traffic noise reduction devices

This dual functionality reduces the need for separate acoustic panels, minimizing installation time and material layering.

3. Tunnel-Compatible Dimensions and Weight

These dimensions allow for long-span coverage without overloading wall fixings or linings:

• Standard width: 1000 mm
• Depth: 100 mm
• Maximum length: 11 metres
• Weight: 22.5 kg/m2

4. Surface Finish, Cleanability, and Durability

Panel Rock is available in custom RAL colours, allowing for seamless integration with tunnel aesthetics or safety zone markings. The surface is:

• Weather-resistant and frost-proof
• Cleanable without chemical detergents
• Durable under continuous operational exposure

5. Installation Method: Secure and Scalable

Panel Rock is installed using horizontal omega-profile sections and self-drilling screws. This system is designed for:

• Quick, non-adhesive mechanical fixing
• Resistance to thermal expansion or contraction
• Simple inspection, maintenance, or panel replacement
• Compatibility with irregular tunnel profiles or segmented concrete linings

Kubri Engineered Solutions: Trusted Solutions for Australian Infrastructure

At Kubri Engineered Solutions, we support Australia’s most demanding infrastructure projects with structural protection systems built for certainty. We partner with premium global manufacturers, including Panacor, Maurer, and Eco EarthTec, to deliver high-performance components backed by decades of engineering excellence. Each product is carefully selected for its suitability to Australian conditions, and every system we supply is supported by technical consultation and post-installation service.

Speak to our team to discuss your next project requirements.