North Goonyella Coal Mine

North Goonyella Coal Mine
Ardent Underground
Techniques Used: 
Large diameter rotary drilling (blink sink)

Project Brief: Expansion on the North Goonyella Coal Mine required a large 7m diameter shaft be constructed to some 250m depth. Due to expansive clays and soft rocks in the upper 85m of the strata, reverse circulation drilling could not be utilised and conventional rotary drilling techniques had to be adopted. This shaft at the time of construction was the world's largest conventionally drilled shaft.

Geological Conditions: Low to medium strength sedimentary and metamorphosed rock were present over the upper 85m of the shaft with fractured zones of clay seams common throughout.

Scope of Work: Vibropile were engaged by Ardent Underground to drill the upper 85m of the 7m diameter shaft by conventional rotary techniques in dry conditions, i.e. without the aid of drilling fluids to support the excavations. The reason for this was the concern that expansive clays and soft rocks would react with water and lead to the collapse of the shaft. Vibropile fabricated in-house all the specialist drilling tools required to construct the shaft. Vibropile drilled the shaft in ~ 5m lifts during day shifts and the walls of the excavation were stabilised during the night shift by Ardent Underground, who utilised robotic shotcreting technology for the project.

Conclusion: The use of Vibropile's purpose built, high capacity drilling rigs allowed the project to be completely successfully in extremely challenging ground conditions. No other piling contractor has the experience or specialist equipment for this type of extreme construction.