Stability study and field observation of coal pillar between goaf and unmined top-coal caving face

The stability of coal pillar between goaf and unmined mining face is the guarantee of safety and success in long wall mining.In recent years,with increasing high-intensity production,the opposite mining and excavation is commonly found in coal mining,which results in twice mining dynamical influences of section coal pillar.It impacts the pillar stability and bring challenges to roadway ground control,especially in top-coal caving face.This paper gives theoretical derivation and field observation of abutment pressure distribution law of section pillar between goaf and unmined thick coal seam top-coal caving face.Taking the 20 meters coal pillar between 922 and 923 mining face in Dongpo coal mine for engineering background,firstly,the evolution process of abutment pressure is analyzed after the formation of section coal pillar,the limit equilibrium zone formulas of gob-side and roadway-side of pillar are deduced and the minimum width of stable pillar is calculated; secondly,with the field observation,the area and peak data of pillar abutment pressure before present mining face are found.The data shows that there is an elastic core in 20 meters coal pillar which helps to keep roadway stable.The discovery also help to propose the possibility of coal pillar size optimization and recovery rate improvement.