Published in March 2005 Australian Longwall Magazine

The technique was developed with funding from ACARP (Australian Coal Association Research Program) and in cooperation with several Australian longwall operations by Queensland-based Colwell Geotechnical Services. The aim of the project was to provide the Australian coal industry with a coal mine rib support design methodology and software tool.

Colwell Geotechnical Services’ Mark Colwell said during the development of ADRS it was recognised several geotechnical and design factors affected ribline performance and operational and safety issues essentially dictated the level of performance required. Consequently, ADRS design recommendations were tailored to the Australian coal industry, however, the procedures for data collection and analysis could be applied to other countries’ underground coal industries.

Case history data were compiled from 34 longwall and two bord & pillar operations resulting in 204 case histories with each case history data set being defined by about 130 individual data fields. In addition, monitoring (incorporating stress cells and extensometers) was undertaken at ten collieries to assess and quantify the effectiveness of different rib support patterns and hardware on rib performance.

The monitoring sites allowed for an improved understanding of the mechanisms of rib failure and degradation in terms of its interaction with the installed support and at the various stages of the mining cycle.

The design methodology dealt with mains development and gateroad development specific to longwall mines.

The statistical analyses indicated for the development condition, just prior to and/or during the installation of ground support off the continuous miner, the most important variables that helped predict the rib performance were the depth of cover, the UCS of the coal, and the angle of the heading relative to the major cleat.

For the condition involving longwall abutment loading, the analyses suggested the level of rib support should be based primarily on the development height and the pillar stress level.

“The ADRS program guides users through the design process, allowing them to develop rib support plans based on sound science and a broad base of in-mine experience,” Colwell said.

Colwell said ADRS further demonstrated empirical techniques are particularly relevant and beneficial in dealing with the complexities of geotechnical design associated with underground coal mining.