Hi ttxela

Most live railway tunnels are rarely confined spaces due to the ventilation caused by trains running through them. [Depends on length and other variables].

Disused railway tunnels are likely to be confined spaces but with the level of risk dependent on the nature of each tunnel. There was a publicised case of someone being overcome in a former rail tunnel in Staffordshire. The adjacent canal tunnel is live and not treated as a confined space for narrow boat users passing through. Same risk of ground gases, but in one there is natural ventilation.

But for many decades many disused railway tunnels were readily accessible to "urban explorers" (some of whom still manage to bypass the security provisions that have generally been put in place) - very little harm has resulted from any confined spaces risks per se. 

Tunnels under construction will usually be classified as confined spaces but again with levels of risk varying significantly, partly as often mechanical ventilation forms part of the construction process. But the risks will usually be much lower for e.g. a main bore being constructed with a tunnel boring machine (TBM) than for e.g. any cross passage being hand dug, by people much closer to the face.

The potential for collapse also varies depending on method of construction. Where a TBM is in use, those inside are effectively cocooned. In contrast, the cross passages might be temporarily protected with e.g. sprayed concrete ("shotcrete") until the final segments are put in place. 

For historians this latter process is called NATM (New Austrian Tunnelling Method) which was associated with a collapse during Heathrow Express.

I think your corresponent probably exaggerates the risk to those who might attempt to drag any protestors out (other than potential violence).

Originally Posted by: CptBeaky

It does make me wonder what would happen if the site was cleared above ground and then they just waited for those below ground to run out of supplies. Would this be seen as a failure to protect the protestors as those below ground were also exposed to the hazards you list, along with malnutrion (should the siege go on long enough) and exposure to human waste.

It does appear the protestors had thought of this, which is why they advertised their tunnels before locking themselves down there.

its a policing issue I suspect, I personally would prefer them to wait to emerge and then arrest them 1 by 1.  Sending the police down there would potentially put them at risk, so wait.... a few days wont harm

Originally Posted by: craigroberts76

Originally Posted by: CptBeaky

It does make me wonder what would happen if the site was cleared above ground and then they just waited for those below ground to run out of supplies. Would this be seen as a failure to protect the protestors as those below ground were also exposed to the hazards you list, along with malnutrion (should the siege go on long enough) and exposure to human waste.

It does appear the protestors had thought of this, which is why they advertised their tunnels before locking themselves down there.

its a policing issue I suspect, I personally would prefer them to wait to emerge and then arrest them 1 by 1.  Sending the police down there would potentially put them at risk, so wait.... a few days wont harm

My understanding is that they were evicted by a private security company.

Since the tunnels are in danger of collapse, I believe that they should be filled in with a significant amount of concrete asap without them being evacuated. This will ensure that no employees are put at risk.  

Personally, I applaud the dedication of the protestors. The government has not listened to the conventionally presented arguments about HS2, there is a groundswell of opposition to it, the case for building it was weak to start with and has just weakened as time has gone on. But still the government persists with it. Near where I live, ancient woodlands and habitats have been churned up to make way for this monstrosity of a project.

I thought the age of protest had disappeared in the 1970s, so it is refreshing to see that it is not yet dead. When government won't listen to the will of the people, what choice is left if we are not to raise our voices in protest?