Aug 2014 - Ground Improvement Innovation

An innovative stone column installation method, developed by local company McMillan Drilling, has been applied by Kirk Roberts geotechnical team for

ground improvement work at the 8300 sqm Vodafone headquarter and innovation hub in central Christchurch.

Steve Roberts, geotechnical engineer and director of Kirk Roberts Consulting Engineers confirms that the new method is not only much faster to get organised on site but is vibration free which makes it ideal for congested sites.

Kirk Roberts is working on the Vodafone build through principal contractor and developer Calder Stewart Industries.

Mr Roberts explains:

“Kirk Roberts works hard to identify solutions to engineering challenges. Our biggest ongoing challenge at present is managing time and budget constraints. The Vodafone site building platform is 2000 sqm and Kirk Roberts conducted trials to determine the optimum stone column spacing and depth. Once the investigative work, including CPT and sDMT testing, was completed we were able to get underway with the drilling and really condense the typically lengthy land stabilisation stage. From our perspective this is very exciting and makes a great contribution to rebuild timeframes in a practical way,” said Mr Roberts.

Christchurch based family owned company McMillan Drilling developed the new method for the installation of stone column foundations to enable greater cost efficiency and cost effectiveness. Company director Jaron McMillan highlighted how the impact of the earthquakes had reinforced the need for ground stabilization and improvement work but, at the time, there was little certainty around when the work would actually be able to commence. “ While some people thought the rebuild would swing into action within the first 18 months there were too many unknowns. This meant that as a company we would have been unwise to place any orders for new drilling technology and it became important to look at how we could utilise and leverage what we already had. Our innovative method made it possible to utilise the existing the equipment we currently had in New Zealand by attaching patented tooling and some additional hydraulic and mechanical components,” said Mr McMillan.

The method involves displacing the in-situ soil laterally with installation of the probe, then gravel is fed from a hopper, through the central tube, and is compacted vertically and horizontally by an internal feed screw. The probe is 400mm in diameter, yet the completed columns are generally 600mm to 900mm in diameter achieved by the compaction of the inner feed screw.

McMillan Drilling developed the prototype in 2011 and have been trialing it at a number of building sites – much to the delight of construction and engineering companies who are, typically up against some pretty tight deadlines. According to Jaron the level of interest the company has subsequently secured has been excellent.

Aug 2014 - Ground Improvement Innovation

Posted in Geotechnical, News/Events