THE DEPARTMENT of Mines and Petroleum has released an official safety warning following a fatality after a rock fall during support cycle in a high heading development.
This incident follows from another fatal accident when an employee was killed by a rock fall while rock bolts and mesh were being installed in a high heading development drive.
This report includes recommendations made by the Coroner following an inquest into the circumstances surrounding the mining incident.
The Department says that a standard high heading development was being advanced with four metre long rounds by drill and blast methods with a twin boom jumbo. The authority claims that support specifications using split set rock bolts and weld mesh had been developed and were consistent with accepted geotechnical standards.
The ground conditions in the development area were generally good, but the last round had opened up a small fault zone in the backs and created ground conditions that were “blocky” in appearance.
However in this instance, the jumbo operator was being assisted by a second jumbo operator working as an offsider on the day of the accident. Both operators were regarded as being well trained and experienced employees.
The operator who was offsiding was moving forward with a bolt to place it on the boom of the jumbo when a large rock fell from the back, struck him and pressed him to the ground. He died at the scene.
The evidence from the investigation indicated that the deceased was one or two steps beyond the last row of bolts in a position under unsupported ground when the rock fell.
The Department says that the immediate causes and contributory factors included a change in the ground conditions with a faulted blocky zone exposed in the backs after the last blast.
Additionally, the jumbo operators at this mine normally work on their own but, on this day, another operator was used as an offsider because his jumbo was not available for use.
Also, the operating procedures referred to not working in unsupported ground but there was a lack of clarity in the definition of what comprised unsupported ground. The authority says that because of the configuration of the jumbo and the dimensions of the drive, it was difficult to see with precision if an offsider moved beyond the last row of bolts into the unsupported ground area.
Similarly, the presence of loose rocks on the floor of the drive could have caused the offsider to look down to avoid tripping, instead of carefully observing the backs and the operator working as an offsider advanced beyond the last row of rock bolts into an unsupported area and was struck and killed by a large rock that fell form the backs.
The Department recommends that all employees involved in the operation of high heading jumbo development headings stay under supported ground at all times.
Employers of persons engaged in high heading development must provide a clear definition of what is regarded as supported ground and unsupported ground.
Add a comment