Relationship between deformation of coal pillars in coal seam with rockburst hazards and protection of surface buildings

It is essential to ensure the long-term stability of surface infrastructures by designing a reasonable protective width (or stopping line) of coal pillars. The design of the irregular downhill protective pillars under a surface diversion canal (part of South-to-North Water Transfer Project) in a mine is regarded as the engineering background. First, the govering principles for deformation of coal pillars under the function of long-term high stress in the coal seam with rockburst hazards are proposed by analyzing the damage modes of surface buildings induced by pillar deformation as follows: (1) No rockburst instability damage occurs in strike coal pillars; (2) No instability damage due to strength decrease over time takes place in strike coal pillars; (3) The deformation of dip coal pillars is uniform so that tensile damage does not take place on surface. Second, an evaluation model for pillar stress is established, and the design method for keeping pillars to be stable and surface buildings to be safe in a long-term period is proposed according to the spatial structure in the overlying strata. Finally, the stresses of coal pillars, stability of surrounding rock and deformation stability of the engineering case are analyzed, and the safety evaluation for diversion canal project and undermine mining design is carried out. The results are of great guiding significance for the width design of protective coal pillars in similar mines.