02-28-2014, 01:55 PM
Rainyjim,
I would assume this is a basic residential application. Use of a back hoe to test the stability of the rock is a wise first step.
Second, because of the random fracture/layering nature of the lava rock and because you've no way to determine the density and integrity, the best rule of thumb is to sink as deeply as possible and use epoxy to set the rebar. 1/2" bar - 5/8" hole etc. The epoxy should billow out of the hole somewhat when the rebar is fully sunk.
Use of a 16" roto-hammer bit should suffice in most cases for establishing depth.
Hope that makes sense and helps out.
I know it sounds extreme but ground acceleration and a house load are equally extreme.
I would assume this is a basic residential application. Use of a back hoe to test the stability of the rock is a wise first step.
Second, because of the random fracture/layering nature of the lava rock and because you've no way to determine the density and integrity, the best rule of thumb is to sink as deeply as possible and use epoxy to set the rebar. 1/2" bar - 5/8" hole etc. The epoxy should billow out of the hole somewhat when the rebar is fully sunk.
Use of a 16" roto-hammer bit should suffice in most cases for establishing depth.
Hope that makes sense and helps out.
I know it sounds extreme but ground acceleration and a house load are equally extreme.