At this time of uncertainty it has given a number of us time to think and ponder some of the more interesting or controversial areas of tunnelling and life. The ATS will be presenting these pieces of writing from our membership and we welcome submissions.
The conditions of the article publication are:
Author must be an ATS member
Writing must have at least a tenuous link to tunnels or tunnelling
Pieces shall be reviewed and chosen by the ATS Executive
Please submit your article to firstname.lastname@example.org with the subject line Tunnel Thoughts.
If engineers do one thing well it is listen to the design engineers, evaluate the numbers and their results and as such construct safe and usable structures built both high and dug deep in the ground. The science of climate change is unequivocal and the evidence (bushfires, flooding, cyclones and droughts) is manifesting itself at a faster and faster rate as society seems to carry on oblivious to the enormity of the consequences. Today it is a clear and present threat to civilisation, a threat that should have been addressed 40 years ago and is now front and centre for us, our grown up children and their children to do the heavy lifting in solving. Before the eighteenth century, when humans in the industrial west began to burn coal, oil and gas, our atmosphere typically contained about 280 parts per million of carbon dioxide. We have to recognise that those are the conditions 'on which civilization developed and to which life on earth is adapted.' Now, as the use of fossil fuels spreads through the world, the amount of carbon in the atmosphere is skyrocketing — we’re now well over 415 parts per million of CO2 in the atmosphere. (1) This Co2 has formed a blanket around the planet trapping the heat and so warming the atmosphere. Our oceans have absorbed 90% of this trapped heat having a catastrophic effect on the climate and the earth, such as detrimentally changing weather patterns forever and bleaching the coral reefs to extinction. [...]
Filling the NFPA 502 void Michael Beyer, Conrad Stacey, Arnold Dix This article should be read as continuation of our earlier part one note to the ATS about Annex D of (NFPA 502, 2020). It proposes a value for critical velocity, filling the void to be left by the intended removal of Annex D from NFPA 502 in a practical way, and also offers internationally acknowledged fire response strategies, and air speeds that could be used in those strategies, for smoke control in tunnel fires. The tunnel ventilation system plays a key role in providing acceptable air quality for tunnel users during normal operation as well as in smoke control and providing tenable escape conditions during a fire. The realisation of the first task is often relatively clear, whereas the control of the tunnel ventilation system during a fire is subject to debate. A comprehensive overview of different ventilation control approaches during a fire is given in (Sturm, Beyer, & Rafiei, 2015), but will be more briefly summarised in this article. Read the article below or download a copy in PDF format by following this link.
Critical velocity and the significance of the imminent retraction of 2020 NFPA 502’s Annex D critical velocity equations Part One
Michael Beyer, Conrad Stacey, Arnold Dix This note summarises what was discovered in a review of the technical background for the change to the critical velocity values resulting from Annex D of (NFPA 502, 2020), as well as the recent developments regarding the critical velocity in Annex D of (NFPA 502, 2020), and why a retraction of this formula is imminent. It is very significant for road tunnel design in many parts of the world. The everyday objective of a tunnel ventilation system is to provide a safe environment for all tunnel users by diluting vehicle exhaust gases and particulates. In case of a fire, the focus becomes the control of the smoke, to provide tenable escape conditions for the tunnel users and access for attending emergency services. With vehicles becoming cleaner, the fire case now generally controls design, in terms of the required ventilation power, the costs, and the tunnel safety. Different countries have some very different approaches and philosophies on the control of smoke in tunnels. A brief overview will be provided here but a more comprehensive discussion about the different ventilation philosophies during a fire, and the different applied velocity approaches, is given in (Sturm, Beyer, & Rafiei, 2015). European approaches do not rely upon high tunnel air velocities to prevent any upstream propagation of a hot smoke layer. Especially for bidirectional traffic and tunnels with high congestion, European standards refer more to a ‘low velocity’ philosophy to preserve any smoke stratification, reduce the potential risk [...]