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$13m Woolworths project relies on rock anchor works installation

Supplier: Antec Engineering
16 June, 2015

Fusion Civil, a Newcastle based operation, were awarded the contract to supply and install the rock anchor works at the new $13m Woolworths development in Nelson Bay.

Project description

Civil works including perimeter piling and temporary soil anchoring are currently in the process of being installed after the project was approved by Port Stephens council in 2012. The development will feature 3457 square metre shopping centre, including a liquor store and basement car park for 180 vehicles within the site.

With the piling process ninety five percent complete using the Continuous Flight Auger (CFA) method around the perimeter of the project, two hundred temporary soil anchors are in the process of being have been drilled and grouted by Fusion Civil.

The soil anchors are installed, grouted through a spinning head fitted to the drill rig, then after several days are tensioned with hydraulic power packs to limit deformation during the construction process.

The solution

Utilising products supplied by Antec Engineering, an Ingersoll Rand ECM-660 Drilling Rig and ChemGrout's CG500 High Pressure Series Mixer Pump which features a double acting positive displacement plunger pump, the Fusion Crew were able to install 8-9 anchors per day minimum, spaced at 2200mm apart in most cases.

The anchor used is a 35mm Galvanised hollow bar, supplied in 3m lengths, installed to a length of 12m. Using a very low viscosity grout acting as a drilling fluid each hole took 35-40 minutes to drill. Prior to insertion of the third rod, the grouting operator utilised the second tank on the ChemGrout CG500HP to switch mixes to a higher density 0.45 brew.

With good communication between driller and grout plant controller, the twin tub setup proved exceptionally effective at this stage prior to locking off of the anchor and the noticeable increases in ground pressure. The CG500 High pressure Series is perfect for rock anchoring projects where pressures of up to 2000psi (137bar) are required in order to get grout to the end of the drill rod.

The centrally positioned hopper of the ChemGrout CG500HP is fitted with a fine mesh screen preventing grout packaging paper and hardened clumps of dry grout from entering the plunger pump. Having the ability to speed up and slow down the mixing paddle through manipulation of the hydraulic reversible control valve proved incredibly valuable by limiting splashes of grout whilst bags were broken into the mix tanks.

The reversible mixing paddle provides excellent and rapid shearing of the cementitious mix and when reversed continually very quickly creates a homogenous grout mixture ready for pumping.

With respect to its geology, Port Stephens is a flooded river valley. The western sections of the park are sand deposits of fluvial and estuarine origin. The conditions at site are very much sandy. Overall the landscape is the residual surface of a peneplain uplifted during the tertiary period (65 to 1.8 million years ago) and subsequently eroded, leaving the more resistant volcanic rocks as small hills.

Under the supervision of the head contractor ADCO Constructions, the project is scheduled for completion in December 2015 and very much a local project that has attracted significant interest from the local community.