Abstract: In this paper, the longwall-roadway cemented backfilling mining technology is proposed to solve the engineering technical problems in extra-thick coal seam, such as low recovery rate and the difficulty in controlling the mining surface subsidence and overlying strata movement and deformation. Systematically, its layout of filling mining system, main equipment and technics are explained based on studying the principle of longwall-roadway cemented backfilling mining technology in extra thick coal seam. Moreover, the composition and bearing characteristics of the backfilling materials are studied to determine the optimal ratio of cemented filling materials which is well applied to field work, namely the optimal proportion of fly ash, lime slag, cement and gangue are 35%, 10%, 2% and 53% respectively. Furthermore, the slurry concentration is 79% and its uniaxial compressive strength can reach 1.8 MPa. The field engineering application shows that the filling ratio can reach 96.1% and the maximum surface subsidence value is 265 mm when mining 21 meter thick coal seam, namely the surface sinking coefficient is only 0.012 6, which shows an excellent application effects.

Key words: extra-thick coal seams, upward slicing mining, longwall-roadway backfilling mining, cemented backfilling, green mining