Study On Theory Of Disaster Induced By Rock Burst Of Roadway Floor With Wide Coal Pillar And The Prevention Techniques

This thesis is set in the N2105 Coal Face of Yuwu coal mine industry as the engineering background. It focuses on the phenomenon of rock burst occurrence from floor of entering air crossheading which happened during the period from Novemeber 17 th, 2013 to January 23 rd, 2014, and then carries out the research of mechanism and cataclysm of the stress effect of rock burst occurrence from roadways along the goaf with wide pillar. By the meaning of theoretical analysis, numerical simulation and field tests, the thesis studies the dynamics characteristics of coal and rock, the evolutions of stress in surrounding rock of roadways along the goaf with wide pillar and the differences of stress in surrounding rock of roadways along the goaf in the structure of fold, and then field monitoring the stress changes in a wide pillar and the distribution of microseismic in stopes, analysis mechanism of rock burst cataclysm, putting forward the prevention from rock burst occurrence from the floor of roadways along the goaf with wide pillar, and by engineering experiment, drawing the following conclusions.(1)According to the coal sample test data, Yuwu coal mine industry’s 3# coal belong to the class â…¡, so the seam has a weak outburst proneness, and the rock strata of the roof and floor of 3# coal both belong to class â…¡, so the rock has weak outburst proneness.(2)After the mining of face, under the influence of the gob roof, the force in wide pillar near goaf and surrounding rock of roadway retained shows significant spatial and temporal characteristics, mainly law as follows:1) The evolution of Pillar vertical stress is "medial and lateral stress having same value medial stress higher than lateral â†'medial stress lower than lateral," the width of the elastic region reduce from 29 m before the mining to 14 m, roof pressure gradually migrates and concentrates to the roadway retained.2) Face after mining within 14 m, the coal wich is within range of 0 to 16 m distance from the pillar near the goaf side within range of 0 to 16 m coal was plastically damage and stress decreased rapidly.3) Lateral vertical stress of coal pillar(from goaf 16-30m) continues to increase, and when lagging from face at 70 m, the growth rate increased, and when lagging from face at 200 m, the growth rate slowed down, and when lagging from face at 300 m, the growth rate stabilized. This range is the elastic energy main accumulating regions of the pillar.4) Vertical stress increased rapidly within 5m range of medial side of roadway retained, until the occurrence of plastic failure, which failure depth expanded from 3m to 4-5m, resulting in bolt support partial failure.5) Stress continuned to increase in lateral side of roadway retained, and stabilized when lagged Face 300 m. The closer the goaf from roadway retained is, the higher increasing amplitude of stress is, but the lateral stress increasing was not obvious from the roadway 7m. The lateral plastic zone width substantially unchanged.(3)From the FLAC3 D numerical simulation results, failure depth of goaf floor is much greater than failure depth of horizontal stress concentration area of roadway retained, and goaf floor failure area will the "pressure relief channel" of horizontal stress concentration area of roadway retained, which goaf formed reduces the degreee of horizontal stress concentration of lateral floor of roadway retained.(4)From 3DEC numerical simulation results, the difference in the way of shaping and the impacting of movement of the load and other aspects: structure of overlying strata in front of the goaf constantly updated, which can generate sustainable movement load, and the lateral overlying rock structures’ activity gradually weakened and dynamic load weakened after formed. When the pre-crack lay in the old top position in the natural deep fault line, it can increase the effect of pre-crack could increase the vertical stress of the area between the original abutment pressure peak position and the pre-crack position. When pre-crack located dangling exposed rock of masonry beam structure, the pre-crack has little effect on the rock fracture position and final state and also on the distribution of lateral abutment pressure.(5)Temporal and spatial distribution of microseismic monitoring in goaf edge Showing: microseismic activity of goaf is mainly concentrated in nearby the lateral edges of goaf. microseismic activity in goaf edge stop a little earlier than stress stablized time of the corresponding area of roadway retained. For overlying strata structure of goaf edge, microseismic activity of anticline affected zone lasted longer than non-affected zone configuration. Anticline area microseismic activity lasted for 3.5 months, the furthest lagging distance from the Face is approximately 370 m. Effect of non-structural region of microseismic activity lasted for 2.5 months, the furthest lagging distance from the Face is approximately 250 m.(6)Based on the rock burst of impact occurrence starting theory, combined with earlier theoretical analysis and field measurement, the thesis concluded that rock burst load source of entering air crossheading of the N2105 Face formed by the growing concentrated static load in wide pillar elastic region behind goaf and the concentrating dynamic load superposition caused by the lagging activities of overlying strata of goaf edge in fold construction area. Using security "Rheology- mutation" theory to analyze the mechanism of instability hazards of the floor of roadway along goaf, and dynamic effects caused by the failure structure of overlying strata movement, which accelerated disasters.(7)The prevention and treatment of wide coal pillar roadway rockburst can prevent from the start and release rockburst energy in two aspects, namely, to reduce the amount of energy and reduce the residual energy release rate. Presplitting basic roof blasting method to control gob roof fracture and pressure transfer.Using large diameter drilling for wide coal pillar release in potential starter zone. Using strengthening support methods to improve roadways along impact ability. N2105 Face eliminate the rock burst occurred again. Since intake air trough since January 23, 2014 the impact of the event, as of December 2014, to promote safe working face accumulated approximately 1200 m.