Study on Stress Characteristics and Supporting Countermeasures of Surrounding Rock in Roadway Formed by Composite Roof Cutting in Three-soft Coal Seam

Abstract

To effectively improve the stability of the surrounding rock in the roadway formed by composite roof cutting of a three-soft (soft roof, coal, and floor) coal seam, the force deformation characteristics of a roadway self-formed by roof cutting were analyzed through similarity simulation, numerical simulation, and field measurement under the engineering background of return air groove on 12406 working face in Selian No.2 Mine. The results showed that a significant pressure relief effect was achieved when the advanced supporting pressure periodicly moved forward to the presplit and cut roof, the stress concentration coefficient on the entity coal side was reduced by about 0.5, and the surrounding rock stress in the roadway was effectively improved. The surrounding rock deformation and the supporting force presented asymmetric distribution characteristics, the deformation rate exhibited a three-section law, and the stress in the gob displayed the recovery characteristic of circular progressive increase from the perimeter to the center. Considering the spatial geological conditions of this mine, a collaborative and integrated surrounding rock supporting countermeasure with "NPR constant-resistance anchor + hollow grouting anchor + retractable U-steel + floor bolting and grouting +door-like scaffold" as the core supporting structure was proposed. The results of the test section manifested that the surrounding rock deformation in the roadway was significantly educed compared with the original supporting scheme.