As part of a sewer upgrade, three tunnels were mined between four shafts, in Athens, Georgia. Tunnel lengths ranged from 116LF of 700LF, with diameters between 58.5″ ID to 9×9 arch segments.
In order to keep the carrier pipe from floating during grouting, the maximum allowable grout density was 70lb/cuft, and the minimum compressive strength was 200psi. Material had to be highly mobile, to facilitate placement through the 700LF of tunnel.
CJGeo proposed 38lb/cuft cellular grout to the tunneling contractor. Over a period of three days, CJGeo batched and placed 1320CY of cellular grout. Batching was performed utilizing an onsite dry mix plant, which was fed directly by bulk cement trailers, minimizing the required laydown area on a very tight site.
Because of the very low grout density, the carrier pipe only needed to be braced by filling it partially with water.