KGA Geotechnical Group Ltd

Andrew Masterton from Mainmark, specialists in ground improvements techniques, visited KGA to talk about their latest research and methods.

Andrew and his colleague, Theo, gave the team a thorough run down on the current techniques for ground improvement and building relevelling using grouting techniques that they have developed as part of the Christchurch rebuild programme. The techniques can be used to solve sunken floors, paths and driveways, cracked walls, unlevel buildings and weak ground. The process involves the injection of resin/grout below floor slabs to evenly and gradually raise a structure without undue stress being placed on the structure. The process is computer controlled providing a high level of accuracy. It is likened to keyhole surgery, where the resin is injected into small holes, which makes for a quick, low mess process with minimal disruption.

The Christchurch Art Gallery Te Puna o Waiwhetu suffered differential settlement following the 2010 and 2011 earthquakes. KGA was involved with the design solution for relevelling the floor of the Art Gallery. A combination of grout injection techniques, ground strengthening with jet grout columns and compaction grouting were proposed. The work was undertaken by Mainmark, who firstly strengthened the foundations with jet grout columns, then slowly went above relevelling the Art Gallery, on average by 2mm a day, over a period of 44 days. The end result restored the Christchurch Art Gallery's design level to +/- 10mm across the entire foundation.

Further details on the services that Mainmark offer, can be found on their website www.mainmark.com.