Bunkers - is it just me?

[farnet]

Ironically I think I'm not going to be able to do much more in the bunker for a while as I've just popped down there and found in a bottom of the dig, in all the spade marks in the walls etc are tiny toads, not a clue how I'd get them out without killing them... I guess they think its safe enough to over winter in.....

[farnet]

Just a thought and anyone who may know better is welcome to shot this down in flames.
Obviously the simplest , safest way is to dig a huge hole cast the bunker and backfill but would it be possible to build one in the same way as wells were traditionally built? In that I mean a circular brick construction which is put in place then further excavations under the brickwork which is then filled in with more brickwork. The brickwork thus provides the walls of the well / bunker as well as providing shoring during the construction .Of course for a bunker the hole would need to be larger and the walls correspondingly thicker and some sort of waterproofing would need to be put in place internally after the whole thing is constructed and that in itself might be problematic if there is a high water table but in essence would such a thing be practical , seems it could be done with much less disturbance and with a degree of secrecy .
Tin hat now on for the expected flak

That was one of my options and I looked into it in detail, I did a lot of reading on arched ceilings and how they were traditionally created, and how amazingly load bearing they are (im talking horizontally), vertical shafts are a completely different matter and that does scare me silly, as I would want to be really experienced and very confident in my skillset the try that. the idea of being at the bottom of a well type design makes me almost feel claustrophobic.

I have thought about it many times, the idea of creating a traditional water well in the garden has a great appeal, but I can't bring myself around to doing that as it really scares me.... and reading up on US forums about it, there is absolutely no room for mistakes and people are killed every year trying to do exactly that over there.

[Devonian]

Thanks Janso,

Devonian

My cousin is an architect, both my sister in law and brother in law are engineers (one structural and one mechanical), I work in one (if not THE) most risk averse businesses in the country, and I'm talking to PHD physicists all the time about what I'm doing.

I do take exception to being trolled like that, if you were really concerned rather than be inflammatory (and showing off) you would have sent a private mail and we'd have had a chat. but it has led to bickering.

A lot of commercial ventures are run by companies that underbid competitors, and in doing so are more likely to employ inexperienced people or are more likely to turn a blind eye to short cuts (to increase their margin). the employees themselves don't have an invested interest and also haven't really looked at the big picture so things like that are bound to go wrong... and in any case I could throw figure around myself, but in what context is it, and how many have successfully managed to dig a trench.

The HSE for example, go too far on the safety, in some aspects and that alone bumps the cost up, which in turn causes 'short cuts', I'm not a personal fan of HSE as I experienced an episode one xmas that due to HSE directives a team of engineers weren't allowed to put xmas lights up in their building due to restrictions... these engineers happen to be the ones that manage the 400KV overhead lines and pylons in this country.... common sense... not likely, it caused a knock on effect which I'm not going to go into.

This is my work, I plan it, I'm careful, I've been doing it in little chunks for a few years, I even pressure test the area multiple times before going down there each time ( commercial grade high strength crow scarers do a VERY good job of that, so anything immediately loose will drop in... which only happened one at the beginning). plus I have multiple acros (vertical and horizontal), done shoring and installed lintels, so tell me Mr. what were the circumstances that caused these accidents?.... soft soil (and no proper analysis), failed shoring, inexperience, short cuts, cost cutting, poor workmanship, tools not fit for purpose all of the above? i'm interested

I don't know you and you don't know me, I'm quite happy to be civil, but don't try throwing your weight around and showing off, it doesn't work with me.

Apologies if you feel trolled, that's never been my intention.

I'm actually a Chartered Civil Engineer, I've done a number of tunnelling projects and now I specialise in construction safety - so hopefully that helps explain where I'm coming from.

Having dealt with fatalities on construction sites, it is not something that I would wish anyone to experience and I was simply trying to raise your awareness to the risks involved. But I will leave it at that and wish you well with your venture!

[Devonian]

Just a thought and anyone who may know better is welcome to shot this down in flames.
Obviously the simplest , safest way is to dig a huge hole cast the bunker and backfill but would it be possible to build one in the same way as wells were traditionally built? In that I mean a circular brick construction which is put in place then further excavations under the brickwork which is then filled in with more brickwork. The brickwork thus provides the walls of the well / bunker as well as providing shoring during the construction .Of course for a bunker the hole would need to be larger and the walls correspondingly thicker and some sort of waterproofing would need to be put in place internally after the whole thing is constructed and that in itself might be problematic if there is a high water table but in essence would such a thing be practical , seems it could be done with much less disturbance and with a degree of secrecy .
Tin hat now on for the expected flak

Yes that is exactly the way it is still done today, except instead of brick, precast concrete sections would be used and then bolted together before a grout is pumped in behind the concrete segments.

The same method is used for horizontal tunnels as pioneered by Marc Brunel with the Thames tunnel in the early 1800's

[grenfell]

Cheers Devonian , bearing with me it seems the Achilles heel of bunker building is that it is pretty difficult to construct one in any form of secrecy owing to the need for machinery , diggers , cranes , earth movers and pumps and unless one can build one in the middle of nowhere ( and even that might be a problem if it involves a lot of traffic ) so hypothetically , hypothetically , it could be possible to construct a brick bunker by hand beneath a large shed without arousing suspicion. Not that I'm thinking of doing that it seems an awful lot of work and expense for something that may have limited potential.
Another thought , I once built a shed over a concrete fishpond , it was empty and made great foundations for the shed and with a trapdoor served as good storage. Reading the local planning portal website it seems it is possible to put in a swimming pool without permission. Could one put in the pool then perhaps wait a couple of years and roof over it again without arousing too much suspicion ?
As I say I've no plans to act on any of this it's more just a pointless mental exercise.

[Devonian]

Cheers Devonian , bearing with me it seems the Achilles heel of bunker building is that it is pretty difficult to construct one in any form of secrecy owing to the need for machinery , diggers , cranes , earth movers and pumps and unless one can build one in the middle of nowhere ( and even that might be a problem if it involves a lot of traffic ) so hypothetically , hypothetically , it could be possible to construct a brick bunker by hand beneath a large shed without arousing suspicion. Not that I'm thinking of doing that it seems an awful lot of work and expense for something that may have limited potential.

As a diy job, then yes it's possible to safely construction an arched brick chamber beneath your shed, but it would be laborious and take years.

In simple terms, you dig down your shaft and structurally line it, then for the horizontal chamber, you should dig the equivalent of one brick depth, then you construct the base, followed by the vertical walls, and finish off with the masonry arch. But the base/walls/arch would need to probably at least 3 courses thick of overlapping bricks (maybe more depending on the size of the chamber) all bonded together to provide sufficient structural strength.

The construction of the arch is however critical, as poor bricklaying, weak mortar, or bad geometry could all result in the failure of the arch/chamber. This really is a job for a skilled mason, rather than a DIYer.

Once the first section has thoroughly cured, the excavation of the next brick depth can commence, then any voids above the previously constructed arch and behind the walls, can be packed out with more mortar.

The construction of the next section of bricks for the walls and arch etc, can then be commenced.

The exercise should then be repeated until the desired length has been reached.

Even with this method, you'll be amazed at how much soil will be excavated, but the bigger risks will be the presence of ground water and rock, even just large boulders!

From a secrecy perspective, using an excavator has the advantage of speed, and so if well planned in a remote area, it is possible it would be done quickly before to many people notice, and if you are using something like a large GRP tank/Plastic pipe, then you can always just say to anyone asking, you installing field drainage or water storage

http://www.weholite.co.uk/product-overview/

Another thought , I once built a shed over a concrete fishpond , it was empty and made great foundations for the shed and with a trapdoor served as good storage. Reading the local planning portal website it seems it is possible to put in a swimming pool without permission. Could one put in the pool then perhaps wait a couple of years and roof over it again without arousing too much suspicion ?
As I say I've no plans to act on any of this it's more just a pointless mental exercise.

Yes planning is a funny beast, as it is concerned primarily with the appearance of the structure and its suitability for the surrounding environment. But for below ground structures there is no visual impact!

For the tunnelling projects I have been involved with, planning has not been required for any of the sub-surface structures. But if there is a 3m by 3m control room above a massive tunnel shaft, then yes the dinky little control room needs planning permission.

[Bad Wombat]

For a super simple bunker how about laying a suitably sized concrete culvert upright on the ground and digging out the soil from inside it? I'm told (i.e. I saw it on the internet somewhere) that the concrete pipe will descend around you as you dig. 100% safe - can't collapse. Some pictures of the method applied to well digging here.

[Devonian]

For a super simple bunker how about laying a suitably sized concrete culvert upright on the ground and digging out the soil from inside it? I'm told (i.e. I saw it on the internet somewhere) that the concrete pipe will descend around you as you dig. 100% safe - can't collapse. Some pictures of the method applied to well digging here.

Yep, the caisson method, occasionally the ring will stick due to friction between the concrete and the soil, but start running a hosepipe around the edge of the concrete ring, and it will suddenly drop scaring the sh@t out of you

But this technique will need some kind of cranage to lift the concrete rings into place, plus the base slab has to be carefully designed to prevent flotation (ie: the whole thing being lifted out of the ground - think about trying to push an empty pint glass down into a bucket of water, providing you do not let water in to the glass, it will jump up and float about half way up the glass, the same thing can happen in the ground as the water table rises). Obviously with a well, it is not sealed and flotation is not an issue