A new cone penetration testing (CPT) service in New Zealand is proving popular with postearthquake reconstruction projects in Christchurch.
Lankelma took its CPT rig out to the region in May to help provide essential information for the rebuild. “I was constantly being questioned about our ability to penetrate the regional shallow gravels and, after many years of working through the river terrace deposits within the London Basin, I felt we could manage the gravel layers here,” says Lankelma engineering director Carlton Hall.
Following good performance using a conventional piezocone, Lankelma was challenged with a site within Christchurch’s Central Business District, where very dense shallow gravels have previously been encountered.
Very dense gravels were reached at 6.5m but Lankelma advanced “pre-push” casing to 9.9m, which was then extracted and the piezocone re-inserted to progress to a depth of 23m into the underlying sands.
Tonkin and Taylor supervising engineering geologist Richard Phillips added that the data has proved to be very useful during the rebuilding work. “The rig is able to puncture through the gravels which is something we had been hoping for,” he says.