GFWAust carried out permeation grouting to a dpeth of 4.9m in dense sands beneath the perimeter walls

The new apartment block at 340 Bay Street was built on a raft on the dense sand foundations. Concerns from the neighbouring property over the imposing loads from the new development on their existing basement retaining wall caused the engineers to propose permeation grouting beneath the slab to improve the strength of the founding sand.

GFWAust were appointed to carry out the permeation grouting. This required over 115 diamond drill core holes through the base slab which varied in thickness from 650mm to over 1.2m, and the installation of grout spears to a maximum depth of 4.9m.

Penetration into the dense sands at depth required innovative changes to the installation of the grout spears including, vibrating hammers and compressed air.

The works were completely successfully in a short time frame required to enable resale of the property. The works were tested by geotechnical engineers including dynamic cone penetrometers (DCP) and coring to confirm the success of the works.