Production during November was 163,999 tonnes ROM, compared to 237,000 during October. Austral said lower production was caused by considerable downtime resulting from continuing equipment malfunction and consequential geotechnical issues.

Geotechnical problems suffered at Tahmoor North were associated with the slow longwall advance rate caused by equipment malfunction requiring frequent stoppages to undertake engineering repairs and ongoing front abutment weighting. This resulted in strata failure of the tailgate and associated face area.

Near face parallel jointing also caused problems for the control of strata, linked with changes in horizontal stress direction as roadway intersections were approached. Austral said significant secondary support was installed to control this, including PUR injection of the affected area.

Maingate conditions have also been affected by a buckled roof and floor heave, resulting in excessive convergence over the maingate drive requiring a doubling in secondary supports through the existing belt road areas.

Austral have also experienced deterioration of the tailgate roadway with extensive guttering on the block side.

Austral said at the same time, an imbalance in the new tailgate drive caused it to continue to rise off the floor throughout the month necessitating some of the roadway support to be cut out to allow clearance for the tailgate chocks to be brought in over the tailgate drive.

The company said this significantly aggravated the deterioration of mining conditions and roof control in the tailgate roadway.

In addition two days downtime were incurred in replacing the new beam stage loader chain in the maingate.

Austral said during the month the Joy 7LS shearer continued to perform below contracted availability levels incurring downtime for warranty repairs.

Austral said the OEMs were addressing equipment deficiencies as a priority however the time taken has been extended due to strata conditions impeding equipment access and the need for production to be given priority.

Austral continues to conduct ongoing monitoring of roadway conditions and where necessary, install additional roadway support.

“It is expected that these measures together with the rectification to the longwall equipment and the ensuing improvement reliability will control the deformation of the strata to manageable levels henceforth allowing the resumption of production approaching budget levels,” Austral said.