Introducing a Model for Road header's Performance Prediction Based on the Specific Energy and the Angle between Tunnel Axis and the Planes of Weakness

Road headers offer a unique capability and flexibility for the excavation of soft to medium strength rock formations, hence; are extensively used in underground mining and tunneling operations. A critical issue in successful road header application is the ability to evaluate and predict the machine performance. The main objective of this research study is to investigate the cutting performance of road headers in coal measure rocks by paying special attention to the influence of discontinuity orientation (alpha angle) and the specific energy. With this respect, a database was established from detailed field data including the measured instantaneous cutting rates (ICR) and geomechanical parameters of the coal measure rocks for each cutting condition through the tunnels in Tabas coal mine project. The database was then analyzed by utilizing the statistical method in order to yield new predictive models. The influence of alpha angle (the angle between tunnel axis and the planes of weakness) on road header performance was investigated and the correlation between them was found to be good (R²=0.96). The analysis of the specific energy also showed that there is a relatively good relation (R²=0.91) between this parameter and ICR. Finally, the new predictive models for ICR (with respect to alpha angle and specific energy) showed to have highly correlated relationships within the limits of measured values and hence may successfully be used to evaluate the performance of medium-duty road headers in coal measure rocks.