The company has purchased a new Herrenknecht AVN800XC that it has been trialling in SE Queensland. The machine is configured to be able to bore holes for 800 mm and 900 mm ID pipes and with minor upgrades the machine is capable of installing 1650 mm ID in most types of ground conditions and is currently drilling in Beenleigh, Qld.

Perry constructed its first vacuum extraction microtunneller in May 2005 in its manufacturing plant on the Gold Coast. The machine has drilled over 1500 m of bores between 400 mm and 600 mm diameter over the last nine months, mostly in rock. Some of the rock strengths have tested up to 150 Mpa. Perry’s Drilling Manager, Robbie Ashton and Plant Manager, Kevin MacPherson have joined their intellectual knowledge gained over many years in the TT industry to produce a high production, long distance microtunneller.

Following on the success of the first machine a second vacuum extraction machine was constructed and started drilling 820 mm diameter holes in rock in April 2006. This unit was constructed with twice the power of the first machine and designed to drill from 600 mm to 1100 mm diameter in most types of ground conditions with potential drive lengths in excess of 200 m using focusable tunnel lasers.

Perry has recently completed two 2100 mm diameter pipe jacking projects. The first was a 160 m drive in Darwin through what was first believed to be soft to medium strength rock. After the first 40 m the Herrenknecht MH3, Dave McMillan, Tony Parratt and the crew encountered backfill consisting of high strength boulder backfill with no cohesive fines to bind the rock together. The fill was under a major CBD road and local knowledge advised the fill was placed by US forces during WWII. The tunnel face could not be excavated without major collapses occurring. During the length of the drive over 200 vertical bores were carried out on the surface, along the bore line, and 160 m3 of grout injected into the ground in an attempt to stabilise the formation. As the vertical bores were completed the tunnelling machine advanced into the grouted formation.

The second bore was undertaken on a freeway bypass in Albury, Victoria. The Herrenknecht equipment was loaded on a road train and shipped to Albury during the Christmas 2005 break as the bore was on the critical path of the freeway project and the unfavourable ground conditions in Darwin delayed the start date in Albury. Once the machine was set up pipe jacking was carried out on a 24 hour basis and 50 m of 2100 mm ID concrete pipe was jacked in by Dave McMillan and his crew in eight days.

Perry has undertaken several long distance microtunnelling drives over the last few months. Two 180 m drives have been undertaken under the M1 Freeway between Brisbane and the Gold Coast, one 600 mm diameter drive and one 750 mm diameter drive, both in rock. Perry is currently undertaking a 218 m x 400 mm diameter bore at Warragamba Dam on a negative 60 per cent grade in Hawkesbury Sandstone. This is a technically challenging bore and Perry believes it will be one of the longest small diameter microtunnels completed in the world, especially in highly abrasive rock.

The fill was under a major CBD road and local knowledge advised the fill was placed by US forces during WWII.