Research on roof structure and support resistance of gob-side entry retaining with roof cutting and non-pillar mining

Based on the mining operation of Dongdong Coal Mine, this paper uses a combination of on-site measurement, physical simulation, numerical calculation and theoretical analysis to explore the roof structure and movement law of the gob-side entry retaining with roof cutting and non-pillar mining.At the same time, the scientific and effective calculation method of the support resistance is further obtained.The research reveals the basic principle for the formation of the “combined short masonry rock beams-articulated rock beams”,understands the law of roof movement, establishes the mechanical structure model and determines the calculation method of the support resistance in the roadway.The field observation and simulation results show that the rotary movement of the roof in the remained roadway results in the asymmetric fracture characteristics of the roadway, the combined structural stability of the cutting control stratum and the basic key stratum is the key influencing factor, the split-breaking of the two along the roadway is a serious threat to the stability of the roadway.The ratio of cutting height to mining height affects the roof structure.Comparative test shows that when the cutting-mining ratio achieves the right range, the control stratum of the cutting roof is prone to “short masonry” structure, and the basic top is the hinge structure of the masonry beam.Therefore, a typical “combined short masonry-articulated” roof structure is obtained.By analyzing the stress state of the support structure inside the entry, the calculation method of support resistance is finally proposed, enriching the coal-face basic theory of rock stratum control along the cut-off roof, which provides a new theoretical basis for an environment friendly efficient mining with roof cutting and non-pillar method.