Australian Projects with NUMA Tools
NUMA tools have been in use for specialised work in Australia since the early 1990's when John Holland purchased the first NUMA RC300 large diameter reverse circulation hammer. This tool is still in Western Australia and has been in regular use on major projects ever since a testament to the durability of the tool.
The RC300 has been used to socket pipes in all sorts of hard rock in sensitive areas this has been achieved by using the centre return of cuttings to reduce contamination of the surrounding area.
Metro Rail project Perth WA.
A NUMA T150 System was chosen to drill critical dewatering and recharge bores in and around the new Perth Metro rail project. The specifications called for a drilling method that did not block off the pore structure of the strata being drilled to achieve maximum permeability in the recharge bores. Rotary mud methods and auger methods were discounted and the NUMA Super Jaws system was chosen.
Each hole had to be drilled to a nominated depth through through fine running sands, coarse gravels, expanding acid clays, broken sandstones, old building materials, tree roots and into a hard sandstone formation. The drill was then withdrawn and casing with slots at predetermined intervals was grouted into place to allow either dewatering or recharge of specific aquifers.
A second monitoring bore was then drilled about 1m from the cased and screened bore and it was grouted the same as the first bore and water level monitoring equipment was inserted in the monitoring bore. The recharge and dewatering bores were then pumped at rates to maintain preset water levels and thus to prevent nearby multi storey buildings from subsiding.
In places there were up to 4 separate aquifers involving a great deal of care with the grouting process if there was to be no disturbance to the surrounding area and buildings or flow of water from one aquifer into a lower aquifer. The SuperJaws performed very well drilling many holes over a six month period and the resulting bores performed to expectations.