FROM EARTH TO SKY

On such a geologically young and active site, specialist geotechnical advice was needed to determine the correct geological model and recommend cost-effective modifications to the foundation design. The main geotechnical issue for Coffey Geotechnics on the Te Puia site was the variability of the soils, says principal geotechnical engineer Peter Bosselmann.

"Geologically speaking, these are young soils which are inherently variable," he says. "The soils are also unconsolidated, which means they are susceptible to settlement under building loads."

To create consistent founding conditions and to minimise the risk of differential settlement of the structures, a ground improvement programme of undercutting and replacing with imported hardfill was implemented. This also helped identify the presence of tomos, underground tunnels formed by groundwater flowing through the highly erodible soils.

During the routine foundation inspections, the team found that ground conditions were slightly better than expected. This allowed the construction team to reduce the scale of the ground preparation works, leading to less undercutting and hardfill replacement, and savings of time and money. Coffey Geotechnics' geotechnical engineers also mapped the site to flag geothermal hazards such as steam vents.

For details, contact Coffey Geotechnics, phone (09) 523 5626. Email: peter_bosselmann@coffey.com.au.

Story by: Trendsideas