Mining scheme design for super-high water backfill strip mining under buildings: a Chinese case study

Considerable coal resources are buried under buildings in No. 5 mining area of Hengjian Coal Mine, which greatly shortens its service life. Working on the premise that the degree of mining-induced damage to surface buildings should not exceed the protective indicator, the mine proposes to use super-high water backfill technology so as to ensure maximum exploitation of these resources. However, according to monitoring of observations of surface movement in the first-mined 2515 working face, mining-induced damage to the surface buildings will exceed level I if this technology is also used to exploit other working faces. A technology combining super-high water backfilling with strip mining is proposed. Numerical simulation is used to study the influence of different retaining pillar widths on surface subsidence characteristics. A reasonable design of these combined technologies is achieved based on the numerical simulation and theoretical analysis. Predicted results indicate that the designed scheme can ensure the safety of the surface buildings. These research results provide a reasonable and reliable technical solution for mining of coal resources buried under buildings.