thanks lots Robyn and Keith,Where your walls are 3m is there the possibility of further stepping or terracing by cutting back further into the hillside? One cal almost always use a little fill material elsewhere and if it's decent soil can be used for garden bed building. Taller tank structures are not only harder to build but far more likely to move when stressed.
been looking around for all sorts of big recycled barrels and not much luck there, but nice to hear of the Sydney barrel garden :) Also our walls are from 1m to 3m high in places, so would need multiple barrel heights + they´re more than 20m in length in most terraces, so that would be a hell of a lot of barrels ... which is possibly doable if the 'barrels' are of ferrocement ..
combined with Keiths' comments (and very wary of expensive mistakes)... am thinking whether the most viable option could be tall small diameter (1- 1.5m on the inside) 'barrels' of ferrocement, as 2m columns joined together with metal bars .. to allow drainage in between (and interesting possibilities for vertical gardens in the gaps, which could shade the tanks too)The metal bar connectors are likely to be the place most likely to develop cracks from stresses. If your tanks are going to be 2m in diameter that's a substantial volume and when filled will provide fairly strong resistance all by themselves. You might consider building dry-laid stone walls in the gaps of 1/3-1/2 meter where hydrostatic pressures would be naturally relieved by the porous nature of said walls. They would require some degree of slant into the hillside so that gravity helps hold them in place. Even where frost heave is a factor the stones that are pressed forward can fairly easily be bopped back into position with a rubber mallet when gravity itself isn't enough to let them slump back into position. Gravel and finer stone material behind such a wall will also reduce frost heave and hydrostatic pressures.
not sure of the embodied energy of all this being viable, as we're talking a lot more metal and cement ... but on the plus side is the fact that we could start small and make one or two of these 'columns' where the walls are already in need of repair, and only proceed if they stand up to real life conditions.Attachments are not supported. Can you post it at a website or Flickr (Yahoo) or Picasa (Google)? (these are free)
i´ve no idea if this group takes attachments,.. here's an attempt at sending a pic (not to scale).
The other plus is that in terms of water pressure ... we're in dry subtropics with occasional heavy rainfalls in winter season. Massive erosion and most of the water goes straight to the ocean.What types of soil do you have?
but on the farm I´ve observed that where the walls fall down the earth stays up pretty well by itself for quite a while, so am guessing the sideways pressure of the earth on the stone walls isn´t that great - unless it gets very wet ... which would be when the tanks are fullest too, so this is another good point: matching altibajos..
If someone comes up with an energy-efficient (elegant & multi-functional) way of collecting water on small-scale farms we'd leap light years ahead in terms of sustainability here. .. which is why am interested in trying out new things whilst we go about solving our own small scale challenges on the farm.--
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