The Queensland Mines Inspectorate said this incident was one of several involving dozers from 2022 and 2023.

It recently flagged several dozer incidents.

In this incident, which occurred in November 2022, the previous shift had built a ramp on the stockpile to the assumed position of the coal valve in preparation for train load out.

At the time of preparing the stockpile, the coal valve was closed.

QMI thinks it probable that the valve became bridged partly due to pushing significantly beyond the valve position.

The site applied physical indicator poles outside the stockpile footprint for dozer operators to use as a visual reference.

This visual reference provided only one part of a grid reference required to identify the void's actual position.

The indicator poles were not necessarily visible by dozer operators at all times because of the height and shape of the stockpile.

There were no other indicator poles to provide a secondary right angle reference point for the void position, however, the reclaim conveyor was commonly used for this purpose.

During the shift when the incident occurred, there were two dozers assigned to stockpile push operations for train load out.

Just prior to the incident, the operator of the dozer number one, the machine involved in the incident, had line of sight for the second dozer.

Dozer number two was on the southwest side of the stockpile.

The operator of dozer number one assumed dozer number two was pushing into the coal valve position.

Dozer number one's operator also assumed coal was flowing due to coal dropping off the blade of dozer number two.

There were no positive communications made between the two dozer operators at this point.

"At the site where the incident occurred, it was a requirement of the site's standard operating procedure to visually confirm the coal valve location when the coal valve turned live," the inspectorate said.

"On this occasion, the bulldozer push started before operators visually confirmed the coal valve location."

Dozer number one pushed coal to where the coal valve was thought to be from observations of dozer number two.

Dozer number one conducted a second push to the same position and while reversing slumped backwards into a void created by the coal valve, which was behind the machine, and the material thought to be bridging the valve letting go.

The inspectorate said the operator was recovered by the Emergency Response Team without injury.

"SSEs should identify operational areas that are considered to be 'high risk tasks'," it said.

"Some examples are, but not limited to, coal stockpiles, working near bodies of water, bund construction or bench preparation in areas identified by section 18 of the Coal Mining Safety and Health Regulation 2017."