Thursday, March 29, 2012

The ramming plan

I basically have four panels to ram - three are 2000mm long, one is 2100 (and there’s also the infill above the door, which is 900 long, making for a 9m wall in total). I’m ramming the wall 400mm wide, for two reasons - firstly, the engineering spec suggests (but does not require) a 400mm base tapering to a 300mm top, but I think it will be much easier ramming the wall parallel. The second reason is that the panels have internal reo mesh, so the additional width will be welcome space during the ramming.

The fact that I have one 2100 long panel complicates the forms a little, but not by much - it means I have one additional set of holes for clamping bolts, but I should be able to blank these with some appropriate sized dowel when I don’t need to use them, and hopefully this will prevent the wall being damaged by “plugs” of earth being torn out when the forms are removed.

So this first illustration shows the assembled forms for the 2100 long wall panel, with reo in place. Each 600 high form is secured by two bolts on each end, and will be bolted in four places to the form above when that is placed.

Note that the column which forms the end of the wall has a “plain” surface - with my layout there will be no need to pass bolts through the joint which this column forms, so I can avoid the disruption to the end surface which would be caused by the grooves necessary to allow the bolts to pass through.

After this panel is rammed, the columns are moved to the other side of the doorway to form up the first 2000 long panel. Note that one column will have a block fitted to form a rebate in the earth wall, in order to allow positioning of the lintel prior to ramming the infill above the door. The through bolts miss the wall completely on the doorway side (again, keeping the surface smooth) but pass through the column at the joint between the wall panels at the other end.

And again with ramming in progress.

The columns and forms are then moved to the other end of the wall, leaving a gap which will be filled in last. Note the tapered rebate formed in the wall as a control joint - this will be lined with foam to keep the wall panels physically separate, and allow any expansion or movement without causing cracking. Not that the wall will go anywhere anyway, but it’s in the spec.

Then finally, the columns are removed and the forms clamped against the wall panels. For this one the through bolts pass through the joint between the wall panels, using the semi-holes left by the bolts when each was rammed.

So this is the plan. I aim to get the forms pretty much complete this weekend (in addition to the core filling of the retaining wall.. wish me luck!) and potentially ram another test block using these forms and the actual wall materials over the Easter weekend, then get into the ramming proper the weekend afterwards.

Any volunteers? :)

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