Analysis of unsupported roof spans highwall mining at Moura coal mine

Highwall Mining has been conducted at Moura Coal Mine since 1993. During that time period. four different high wall-mining systems have been used. One common constraint with three of the systems was that all drives were 3.6 metres wide and they were where unsupported. The roof conditions vary from pit 10 pit, seam 10 scam and within a single reserve block. The roof stability was analysed for each pit and for areas within each pit. The analysis ranged from empirical methods 10 finite element and numerical analysis. A large amount of geotechnical information was obtained during the exploration program. In most cases a Rock Mass Rating (RMR) system such as Inc Coal Mine Roof Rating (CMRR) was sufficient for estimating the potential stability of the immediate roof strata.