Deterioration of Coal Microstructure under Discontinuous Cyclic Loading Based on Nuclear Magnetic Resonance

To study the damage and destruction behavior of small coal pillars in mine roadway driving along gobs under long-term in-situ stress multiple engineering disturbances, an unconfined compression experiment a discontinuous cyclic load was designed, with holding time as variable. An electro-hydraulic servo rock testing machine used to impose on sample perform final uniaxial compressive strength test. The changes pore number diameter were monitored by nuclear magnetic resonance analysis. increase loading resulted significant pores sample; porosity continued increase, proportion changed. micropores decreased gradually, whereas mesopores macropores (cracks) increased. degree internal specimen increased time, which gradual decrease strength. Therefore, action stress, improve bearing capacity pillar while avoiding gas water influx into working face goaf, should be reinforced multi-layer multi-grain grouting.