Research and application of pre-excavated double withdrawal channel technology without coal pillar abandonment

In order to solve the problem that the surrounding rock control of the pre-excavation double-retracement channel is difficult and a large number of coal pillars cannot be recovered. Taking chuancaogeban coal mine as the engineering background, the mechanical model in the process of gradual connection between coal mining face and main withdrawal channel is constructed, and the response characteristics of surrounding rock in withdrawal channel are simulated and verified by FLAC3D numerical calculation model. The instability mechanism of this kind of roadway is revealed, and a comprehensive stability control technology of surrounding rock and the technology of recovering all coal pillars are proposed, and the field engineering verification is carried out. The results show that when the coal mining face is close to the main retracement channel, when the distance between the coal mining face and the main retracement channel is 4 m, the coal body between the coal mining face and the main retracement channel enters an unstable state. Using 8 m wide filling wall to replace the coal pillar between the main retracement channel and the auxiliary retracement channel can ensure the stability of the surrounding rock of the two retracement channels after the coal mining face passes through the main retracement channel. In addition, the retained auxiliary withdrawal channel also has the functions of auxiliary production and coal pillar recovery, and finally realizes the technology of pre-excavation double withdrawal channel without coal pillar abandonment. As the coal mining face gradually approaches the main retracement channel, the surrounding rock stress of the main retracement channel and the auxiliary retracement channel has significant dynamic development. Based on the development law of the deviatoric stress of the surrounding rock, the combined control technology of ' pre-cutting roof + high water material pillar + grouting reinforcement + single pillar + metal mesh + steel ladder belt + bolt + anchor cable ' in different regions is proposed. The field monitoring results show that during the removal of coal mining equipment, the surrounding rock deformation of the withdrawal channel is small, the surrounding rock control effect is good, and the equipment is safely and efficiently removed; during the recovery of coal pillars, the surrounding rock deformation of the retained auxiliary withdrawal channel meets the needs of production. The recoverable resources of coal seams will increase by 747,000t, and the economic benefits will increase by 117 million yuan.