Fully mechanised mixed mining technology involving solid backfilling and caving methods in longwall workface

Consolidated backfill mining technology has been widely popularised in China. However, the complicated backfilling and mining processes as well as low productivity of the backfilling and mining workface has made it more difficult for collieries to survive during the downturn of coal industry. In this condition, this paper introduces an innovative mining method based on consolidated backfill mining technology, namely, mixed mining technology involving solid backfilling and caving methods, and presents its underlying technical principles. In addition, the paper describes the controlling mechanism of strata movement and its three main systems: underground separation system for coal and gangue, underground crushing system for gangue, and fully mechanised mixed system involving mining and backfilling. An engineering application of this method at the Pingdingshan No. 12 colliery shows that during a 2-month period in the Ji15-31010 workface, 142 thousand metric tons of coal resources were extracted, with 73 thousand metric tons of gangue being backfilled. In addition, the controlling effect of the strata movement is found to be satisfying and the economic benefits are remarkable.