The New South Wales Resources Regulator has investigated a rib slump at one of the state’s underground coal mines after a worker was injured while carrying out a rib support installation.
Two operators were using an air track when installing secondary rib support. A hole was drilled in the rib and chemical was installed.
The operator retracted the drill rig head plate off the rib to install a rib bolt. The rib slumped, and as the operator pulled his hand away, it was caught between the rig mast and the falling rib.
The wedge of rib coal that fell was about 1500mm high, 700mm wide and 300mm deep.
Before the work started, there was no sign of any deformity and no visual sign of fracture or failure while the drilling was taking place.
The NSW Resources Regulator said the potential for a fatal outcome from rib failure is well understood.
“While there may be no visible signs of potential rib failure, it is imperative that consideration is given to this possibility,” the Regulator said.
“Any risks to operators should be mitigated by implementing appropriate controls.
“The method of bolting that affords the most protection to operators by minimising the risk of coming into contact with a slump or fall of rib should be used at all times.”
Another incident involving a rib slump in 2023 also drew the Regulator’s attention.
Also at an underground coal mine, the slump was 4m long, floor to roof in height and 2.5 metres into the rib. At the time of the failure, the crew was preparing to use the miner to grade through a large reverse fault.
Two workers in the heading were alerted to the failure when they heard coal being sucked along the ventilation tube. There were no indicators of outburst or seismic activity.
The Regulator recommends that all underground mines have a strata management plan that includes:
- a risk-based approach for the development of the plan and supporting procedures. This must include ensuring those who contribute to the development of the plan and procedures have appropriate qualifications and experience.
- identification of the correct support to deal with all anticipated strata and mining conditions identified in geotechnical assessments and arising from ongoing monitoring of strata conditions
- appropriate consideration of the type and extent of support to be installed over the full lifecycle of the roadway
- procedures for the control and rectification of deterioration or failure of installed support
- detailed inspection requirements and TARPS (trigger action response plans)
- training of all applicable employees and contractors in the requirements of strata management systems
- considering the suitability of temporary support fitted to continuous miners.
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