Grout socks are utilised in heavily fissured or fragmented rock. Rock bolts rely on the confinement of grout within a borehole in order to transfer the strength from the steel threadbar into the rock.
If fissures prevent the borehole from containing the grout, then the bar can be covered with a grout sock prior to placement in the hole. Grout socks are formed from a poly-cotton mix textile with high elasticity and strength but low permeability. As the grout fills the sock, the solid particles clog within the sock and fill the borehole. The cementitious water filtering through the grout sock or ‘grout milk’ then cements the mass to the inside surface of the borehole.
DYWIDAG Grout Socks can provide the same confinement in ground with fissures as would be expected in normal bolting conditions.
Care needs to be taken when placing the bolt within the grout sock to prevent tearing as this will reduce or negate the effectiveness of the sock. Care also needs to be taken when placing the bolt into the borehole as the rough surface left by drilling can cause damage to the material.