Improving coal recovery from longwall top coal caving

Abstract

This paper develops a series of methodologies to improve the recovery rate from longwall top coal caving. Cavability of top coal is the most essential indicator to estimate the recovery rate. Some influencing factors of cavability such as unconfined compressive strength, abutment pressure and thickness of top coal are primarily analysed to provide cavability assessment. The methodologies of how to determine the most effective drawing interval and cutting to drawing height ratio are developed to improve the recovery rate of top coal. Drawing interval can be determined as the advancing distance of hydraulic support between two caving processes. Both drawing interval and cutting to drawing height ratio can be artificially altered to the optimized value to improve the recovery rate. Three blasting patterns including five-hole scheme, rectangular scheme and triangular scheme are analysed to determine the most effective pattern for top coal caving. Arch structure formed in the caving process is another reason of causing a low recovery rate. In order to improve the recovery rate, a new method of vibration technique is analysed in this paper to break the arch structure.