In a continued effort to stay abreast of new technology in geotechnical investigations and exploration drilling, drilling and testing service provider to the geotechnical and minerals exploration market Geomechanics, part of Southern Africa-based GeoGroup, has acquired a R7-million track-mounted drill rig, manufactured by Canada-based sonic drill manufacturer Sonic Drill Corporation.

The Sonic 450-24 drill rig, which was delivered to Geomechanics’ Johannesburg-based facility in February, bores up to five times faster than conventional drill rigs in ground conditions where sonic drilling is more appropriate. It is also able to provide continuous core samples, six inches in diameter, to depths of up to 200 m.

As a result, sonic drilling can be employed in many applications, including geotechnical and geothermal projects, environmental investigations and mineral exploration.

The sonic drill rig, therefore, offers many advantages over conventional rotary core and percussion drilling techniques in overburden ground conditions and promises superior information collection and a waste reduction of up to 80%.

“This product can be used for well construction and reduces the risk of project failure in unknown or difficult subsurface conditions where excellent core collection is an essential requirement. It also enables more to be done with a single borehole because it can advance a temporary outer casing as the borehole is drilled,” says GeoGroup CEO David Rossiter.

He adds that sonic drilling will be particularly valuable when drilling in sand and soft ground conditions, where core samples are difficult, time-consuming and expensive to produce using conventional methods.

“The exploration of mineral sands was previously undertaken using reverse-circulation or vacuum drilling. These methods produce dry samples well but do not work well in overly saturated conditions,” explains Rossiter.

“The sonic method of drilling, however, uses vibratory energy and slow rotations to produce core samples. It has, therefore, become the most apparent solution to provide core samples in sand, clay and soft, saturated ground conditions.”

Sonic Drill Corporation’s patented Sonicor 50K drill head sends high-frequency resonant vibrations down the drill string to the drill bit, while the operator controls these frequencies to suit the specific conditions of the soil and rock geology.

Resonance magnifies the amplitude of the drill bit, which fluidises the soil particles at the bit face, allowing for fast and easy penetration through most geological formations. An internal air spring isolates these vibrational forces from the rest of the drill rig.

By providing the necessary rotational and vibrational forces, the sonic rig is able to core and case holes in soft and saturated overburden material, drilling easily where most other rigs cannot.

Geomechanics made the decision to invest in the sonic drill rig in July 2012, acting on its long-term vision to enhance mineral sands exploration services and gain the upper hand in terms of difficult drilling ground.

Rossiter tells Mining Weekly that training on the drill rig has just been completed locally by Canada-based sonic drill training guru Randy Pruden.

“Twelve eligible delegates were trained and we received positive reports back from the trainer on the competency of our staff and their natural drilling ability,” adds Rossiter.

Geomechanics is currently awaiting the delivery of specialised rod strings and core barrels, manufactured in Germany, which will complete the acquisition.

Rossiter believes the sonic drill rig will speed up conventional geotechnical investigations and mineral explorations. “As a result, we can offer our clients significant cost savings in professional supervision, which will make us more competitive,” he says.

However, Geomechanics will not be expanding any further in the short term as it remains focused on tailoring its business to sync with current market trends.

“We are also focusing on improving our competitiveness by cutting costs and improving production efficiency, which will give our clients the benefit of a more cost-effective product. I believe this will strengthen us for the future and will produce better margins, providing us with security in the market place going forward,” says Rossiter.

He adds that, while changes in the market in recent years, owing to the global economic downturn, can be see as negative, Geomechanics take them on as a challenge and part of a natural cycle.

“We look to the future and strive to better ourselves, to establish the GeoGroup as an industry leader,” he concludes.

Geomechanics currently has over 60 drill rigs in its fleet, stored in its 4 000 m2 in-house engineering workshop, which maintains existing rigs and constructs new ones.