Tunnel Projects

One of the most important design issues for major tunnelling projects is fire and life safety and achieving compliance with associated regulations. Emergency ventilation and evacuation are crucial to tunnel safety, but fire safety sub-systems (such as fans and intervention shafts) are expensive and may severely constrain the design of a project.

Traditional, prescriptive approaches to these design issues are not only costly but do not necessarily provide an adequate level of safety. Through our unique performance-focused design strategies and proprietary tools, Stephen Grubits & Associates will rationalise the fire- and life-safety requirements of your tunnel project, achieving demonstrable compliance with regulatory objectives for the minimum project cost.

Performance-based approach

Using a performance-based approach to fire and life-safety in tunnels, SGA offers superior design and construction methodology as well as best-practice safety outcomes. Our teams of experts work to:

How we work

First we generate a list of possible scenarios by constructing an ‘event tree’ whose branches represent alternative events. Such an event tree explores, for example, what happens when:

By linking a sequence of branches, or events, we can construct a path, or scenario.

We estimate the probability of the event for each scenario occurring, based on historical data and predictions of reliability. We then evaluate the probable occurrence of each scenario by combining the probabilities of the branches it contains.

Fire modelling techniques and fire-safety analysis are used to predict the consequences of each scenario in terms of death and injury. Finally we calculate an overall level of risk, based on the consequences and probability of each of the scenarios.

In cases where some of the variables are better defined in terms of probability distribution functions rather than discrete values, we adopt a ‘Monte Carlo’ simulation approach to predict the probability distribution of expected outcomes. By running many thousands of computer simulations of a wide range of scenarios, statistical inference can be drawn on the relationship of the outcome to the input variables. Thus the sensitivity of the risk to particular variables can be quantified. This provides the information necessary to identify the main factors contributing to the predicted risk and which measures are most effective in controlling them.

Deterministic fire modelling

Our computational fluid dynamics (CFD) modelling capability lets us design optimal smoke controls for even the most complex tunnel systems. Our egress and rescue deployment models permit accurate prediction of these activities within the context of an emergency event. We produce designs allowing the management of a range of credible worst-case scenarios to achieve acceptable outcomes consistent with defined objectives.

System risk evaluation

This strategy uses quantitative risk assessment (QRA) to build on deterministic fire modelling. We’ve developed a software package called TRAFFIC (Tunnel Risk Assessment For Fire Incidents and Catastrophes) to tackle the unique problems associated with regulatory compliance in tunnel design. TRAFFIC is similar to QRA, incorporating deterministic modelling of fire phenomena, egress, system reliability and responses to emergencies into an overall risk framework.

Client benefits

Stephen Grubits & Associates provides cost-effective, innovative smoke control systems to meet exacting requirements.

Because we have technical expertise in understanding and predicting smoke and evacuation behaviour, we can design solutions from first principles. For example, we can:

Our performance-based approach identifies fire-protection systems that are both necessary and cost-effective, bypassing expensive features that contribute little to overall tunnel safety. Not only that, but our multidisciplinary team of engineering, computing, regulatory and emergency experts are on call throughout the construction process, assessing design changes as they happen, monitoring implementation and ensuring ultimate certification. It is this fully contemporary, integrated approach to fire and life safety which has made us leaders in our field.

Rail Tunnels

Road Tunnels