Naked Science Forum
Non Life Sciences => Technology => Topic started by: Dansercoer on 23/03/2009 04:29:58
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Dear all,
Sorry for posting my second question in three days, that’s only because this forum is new to me. [;)]
I was wondering whether somebody could get me started on my question regarding Igloo (http://users.telenet.be/wouter_de_meester/Igloo.pdf)?
I am looking for the relation between the thickness of the clay-vault (that’s why dimensions and scale are missing) and its weather resistance. In other words; how long would it take for the structure to collapse in certain weather conditions? The clay is natural, not fired and has turf above it, as you would find it in the ground. People could walk over the construction.
Thanks for having read through my post!
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try this ...
http://en.wikipedia.org/wiki/Igloo
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Sorry, where did you see clay mentioned?
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Is this theoretical, or do you plan to construct this igloo as an art exhibition in Hyde Park? If you do plan to actually go ahead with this, have you been in contact with the Royal Parks Authority?
I'm not to sure as to the exact location of this intended structure, but if it is fairly close to one the main surrounding roads (Park Lane, Bayswater Rd, Knightsbridge) you will have to bear in mind vibration from buses and HGVs.
I presume you will be working with wet clay and molding the shape on-site.
A few points that need to be cleared up first:
What time of year?
Will people be allowed to walk on top at any time?
Will people be allowed to walk through the tunnel?
Are you aiming to use only natural substances?
What type of soil will you be putting over the clay?
What sort of period are you aiming for this structure to last?
Other points to clear up:
Have done or thought about a Risk Assessment?
Have you approached any insurers for public liability insurance?
Have you considered the need for a permanent on-site presence?
A structure such as this, which is highly susceptible to weather conditions, would be fraught with technical and safety problems.
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You sure as heck need to know the cation exchange capacity of your clay to know how prone it will be to hydration. A montmorillonite clay, for example, can easily swell by 900% when exposed to water.
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Thanks for the tip Ophiolite.
Don_1:
It was an “interior” design assignment I got three years ago, so it’s theoretical.
I’d like to add it to my portfolio, but I’ll need to present it more realistically.
You’re correct about the vibrations, it’s not too far away from the road dividing Hyde Park and Kensington Gardens.
Here’s an answer to your questions:
What time of year? summer
Will people be allowed to walk on top at any time? yes
Will people be allowed to walk through the tunnel? yes
Are you aiming to use only natural substances? yes, ideally found on the spot
What type of soil will you be putting over the clay? see above
http://www.london.gov.uk/thelondonplan/images/maps-diagrams/jpg/map-3d-5.jpg (http://www.london.gov.uk/thelondonplan/images/maps-diagrams/jpg/map-3d-5.jpg)
What sort of period are you aiming for this structure to last? one month minimum
Have done or thought about a Risk Assessment? May I ask whether you see other risks apart from collapse?
Have you considered the need for a permanent on-site presence? The calculations should make this obsolete.
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What time of year? summer : What sort of period are you aiming for this structure to last? one month minimum
Over such a period of time during (with any luck) a warm dry summer, the clay will dry out. You would need to ensure that the clay's water saturation remains fairly constant. Too dry, it will start to crack, too wet, the base of the tunnel wall will lose its rigidity and begin to spread under the weight.
Are you aiming to use only natural substances? yes, ideally found on the spot
Any natural materials will be subject to drying out and water permeable. Your tunnel would need water retaining fins along its length to stop water runoff when re-saturating the upper wall/roof clay. These could be wood if the tunnel life were not too long, otherwise a plastic might be necessary.
What type of soil will you be putting over the clay? see above
Since your plan shows a grassed covering, you would need a soil which is relatively free draining, however, the need to maintain the saturation of the clay would dictate the opposite. You must also be aware that warm air passing through the tunnel will cause rapid dehydration of the inner surface.
The fins mentioned above would also serve to prevent soil from being washed away during watering.
Have done or thought about a Risk Assessment? May I ask whether you see other risks apart from collapse?
Having spent far too many years in the exhibitions & events industry, believe me, you will be required to show the HSE (Health & Safety Executive) a full risk assessment. You would probably need two risk assessments, one for the construction & demolition of the structure and one for the 'open to the public' period. These assessments would need to include all risks associated with plant machinery (e.g. mechanical diggers, fork lift trucks etc.), traffic marshalling (e.g. deliveries, unloading, waste disposal), use of power tools, use of hand tools, structural damage liability during construction, partial and total collapse of the structure, evacuation of personnel, accessibility for emergency vehicles etc. etc.
For the 'open to the public period' a similar risk assessment would be required which would include liability of people slipping on the slopping surfaces, trip hazards, structural damage, partial or total collapse, evacuation of the area, recovery of injured people.
I can assure you these documents will run to many pages.
Will people be allowed to walk through the tunnel? yes
I very seriously doubt the HSE would allow this or that you would find any insurer willing to underwrite such a risk.
Have you considered the need for a permanent on-site presence? The calculations should make this obsolete.
Since the saturation of the clay is of vital importance, it would need constant monitoring. Although an automated system might be possible, I would imagine both the HSE & any insurer would insist on a permanent presence in the event of an emergency.
I will send you my bill for consultancy!!!
You sure as heck need to know the cation exchange capacity of your clay to know how prone it will be to hydration. A montmorillonite clay, for example, can easily swell by 900% when exposed to water.
Also the shrinkage of the clay during dehydration will be of similar importance, as will the weight of the roof/walls on the base of the walls, which may result in bulging and bowing of the wall and effectively squeezing out water from the clay in this area.
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I was wondering how this (http://fr.wikipedia.org/wiki/Terre-argile (http://fr.wikipedia.org/wiki/Terre-argile)) structure has been made?
Maybe the clay could be fired from the outside like http://www.kumeyaay.info/museums/modern_clay_pottery/pit_firing_pottery.html (http://www.kumeyaay.info/museums/modern_clay_pottery/pit_firing_pottery.html)?
I don’t think the erosion caused by watering will be a major problem;
the scale model is steeper than the actual plan (sorry for that) and the grass will try to keep things together.