How do they plant more explosives? Are there some methods of measuring how safe the building is? Or do they just send a guy inside and wish him good luck?
It would depend on why. Probably start with wreaking ball or something like that.
My WAG is that the demolition expert they hired would know exactly why the explosives didn’t go off and would know exactly how safe it would be to re-enter the building.
On the other hand, you raise a good point if let’s say half the explosives go off and the other half don’t. Now, half of a structurally compromised building is full of explosives (thus not allowing the use of a wrecking ball as stated above) and very unsafe to enter. I would imagine if there were any unexploded explosives left in the building it would create a huge public health hazard and make it nearly impossible to destroy any remaining structures and make cleanup of what did explode impossible as well.
I remember one demolition company talking about being called in to finish up the job another company had failed on. They said the first thing they had to do was wait for a while to make sure the structure wasn’t going to come down on it’s own.
Before they sent a person in, I’m sure they would try a remote control camera vehicle.
Destroy it from without, by people with shoulder-mounted rocket launchers?
Are we talking about downtown Manhattan or an old grain elevator near a rail spur and nothing else?
I’m assuming you are talking about failed implosions (a good start for google). I don’t know it they have any way of knowing if a specific charge:
- Did not explode
- Exploded, but the structural member withstood the blast (not enough explosive? Member not weakened enough mechanically? Charge was improperly shaped?
- Most terrifying: everything went as planned, but you didn’t know what the hell you were doing and have created a death trap.
In a high-density urban situation, I would hope that they could get a crane to begin “eating” the structure from the top down. At least remove as much structure as possible to get down to the level(s) on which the charges were placed.
Keep in mind - those look-so-cool-on-TV implosions are not the result of string charges on every structural member - first they cut away most of the structure and use explosives on relatively few members.
Once all the charges detonate, you are looking a a few thousand tons of structure that no one knows WHY it can stand.
Go in a start throwing grenades? You first.
Maybe pretend it’s Godzilla - a squadron of fighters with air-to-ground missles?
Thanks for bringing up grain elevators.
I was once mowing hay for my uncle and they were destroying an old wooden one. They are made from stacks of 2x4s laid on the broad face. Much like Lego. In other words, they are are tough as hell.
They were using an excavator to chew out one corner of the building. Eventually it gets compromised enough that it falls over, and breaks apart in huge pieces. Big dust cloud from all the grain dust. I imagine fire is a real risk.
It was amazingly fun to watch.
Regarding the cement based demolitions, I believe they leave sacrificial cameras inside nowadays. Against a few million in explosives and labour, even a few dozen hundred dollar cameras will be chicken feed.
I vote that if we can’t get a good answer in another day, this gets kicked up to the Master.
A single charge anywhere near the camera will either destroy it or bury in (opaque) debris - Hey Joe- “#27 is still alive!” “Great! what is still standing?” “A lot of broken concrete”.
With the spy mini helicopters, they might be able to get a clear view remaining uprights by shooting the ceiling.
oh, right, those little machines buzzing around political rallies don’t belong to anybody…
I know the answer to this one! I watched an unsuccessful demolition. The nurses’ home in St Vincent’s Hospital in Dublin (a 1960s building of around 10 storeys) was demolished using explosives. Because of the nature of the site (a working hospital, with an adjacent building that was to remain intact) they tried to use the minimum amount of explosive.
At the blast, the building leaned and partially collapsed but remained upright.
Following a delay of some hours, the demolition was completed using a wrecking ball.
I found a report (PDF) that explains in detail what happened, with pictures.
There’s this failed demolition. Notice all the pieces/parts of the building they removed at the bottom before setting the charges. They eventually used a wrecking ball to get the rest down.
They tried to blow up an old housing project in Providence - didn’t work. Photos at the site below, which some of you will find fascinating.
Did they really think that huge slab of concrete (feed mill) would collapse? A solid slab of concrete designed to withstand the outward force of grain (in bulk, it is a fluid) would crumble by being dropped 10-20 feet?
Next time, punch holes.
I don’t see a decent answer yet from past 10 years. (Thanks Hibernicus, Wrecking crew, etc.)
I’m genuinely interested in the answer. Let’s kick it up to Cecil.
The answer, as with so many things, is very carefully.
There is no one answer, as the conditions of a failed demolition are going to be pretty unique, because the job of a demolition team is to make darn sure that things do not fail - because those consequences are possibly disastrous. They do lots of math and surveying beforehand, so that they use sufficient explosive to ensure collapse (but not enough to lift the building onto the next block). The explosives will be wired with redundant detonation systems, to ensure correct and complete firing. They figure the collapse patterns, particularly if there is small footprint to collapse into. They use electrical detonators, for accurate timing and safety in case of failure.
If, in spite of the precautions, things do go wrong, then the most appropriate and safe method will then be used, after a thorough survey of the site. These days, remote sensing equipment can be used to do this. Most likely, a top-down destruction using a crane and wrecking ball, as noted above, will be the safest way, if not the most convenient or quickest approach. But the focus from the time the original plan failed will be the safe disassembly of a probably unstable structure, without introducing more risk to workers and those around the site.
Popsci has a new article on a new technique of demolition http://www.popsci.com/technology/article/2013-01/demolition-goes-eco-friendly-japan The video is disappointing, though.