Strata pressure laws and control of gob-side entry retaining passing through concentrated coal pillars in medium-thick coal seam fully mechanized mining faces

To systematically reveal the strata behavior characteristics and evolution mechanism of gob-side entry retaining in a medium-thick coal seam fully-mechanized mining face when passing through the concentrated coal pillar section, and to ensure the stability of the entry surrounding rock and safe mining, taking the 31109 fully-mechanized mining face of Cuncaota Coal Mine as the research background, a multi-source monitoring system was deployed for the concentrated coal pillar section and the goaf section. On-site monitoring including bolt and cable stress, roof separation, and borehole peeping was carried out to analyze the strata behavior characteristics and surrounding rock failure laws in different structural sections. The research shows that the strata behavior of gob-side entry retaining has significant stage and zoning characteristics: the ground pressure in the concentrated coal pillar section is intense with obvious hysteresis, and the deep and shallow roof separation develops remarkably; the strata behavior in the goaf section is relatively weak, and the overall stability of the surrounding rock is favorable. Borehole peeping results indicate that roof fractures gradually expand and extend to deep areas with the advance of the working face, and the damage of deep structures is an important cause of borehole collapse. A comprehensive control technology of "advance reinforcement support—fracture zone strengthening—monitoring linkage regulation" is proposed, which can effectively alleviate the problem of intense strata behavior in the concentrated coal pillar section.