Research On The Chain Instability Control Technology Of Room And Pillar Method Goaf Under The Influence Of Dynamic And Static Loads

Room and pillar method goaf left over from shallow mining in mining areas in central and western China not only pose a threat to production safety of surrounding coal mines,but also bring harm to production and living of local residents and economic development.In recent years,large areas of room and pillar method goaf have frequently suffered from instability and collapse accidents.It has become an urgent problem to study instability mechanism and control technology of room and pillar method goaf.Based on national natural science foundation project "basic theory research on chain control of coal mine goaf instability disaster"(51674142),and taking the project "hidden disaster control project in the eastern part of nursing home coal mine field" as the starting point,the chain theory of disaster is introduced to study the chain instability mechanism,chain effect and its characteristics of the room and pillar method goaf by comprehensively using the methods of theoretical analysis,on-site monitoring,experimental testing and numerical simulation.The basic mechanical parameters under the influence of dynamic loading are obtained through laboratory research on acoustic emission damage characteristics and creep characteristics of coal samples under cyclic loading.The chain stages of goaf disasters are divided,and the control technology and method of goaf instability and chain breakage are put forward.UDEC software is used to simulate the instability law of the goaf under the combined effects of mining disturbance and static load,vehicle dynamic load and static load,and the effect of chain scission control of goaf instability disaster is verified on site.The research work is mainly divided into the following parts:1)Stress evolution and deformation and failure characteristics of the coal pillar left behind in the room and pillar method goaf under the influence of static and dynamic loads are studied;This paper makes a preliminary analysis on the causes of instability disasters in the room-pillar goaf of the coal mine in the nursing home.2)The characteristics,evolution rules and chain effect of chain carriers in room and pillar method goaf are studied;The theoretical model of disaster chain effect in room and pillar method goaf under the influence of static and dynamic loads is established,and the instability disaster chain in goaf of nursing home coal mine is analyzed and constructed.3)The mechanism of coal crack propagation instability under dynamic load is studied through acoustic emission experiments of coal samples under uniaxial compression and cyclic loading and unloading conditions.The microscopic damage evolution process of coal pillar is reflected by acoustic emission signal characteristics,and the macroscopic fracture instability process of coal pillar in room and pillar method goaf under dynamic load is analyzed.4)The creep compression test under uniaxial condition is carried out in a graded increment loading mode,and the creep curve,strain variation curve with time,creep rate curve and the like of the coal sample are drawn;By analyzing the creep test curve characteristics of coal samples,a creep model suitable for describing the creep characteristics of coal pillars is fitted,and the effective bearing time calculation formula of coal pillars under creep action is obtained.5)Taking the instability disaster of the room and pillar method goaf in the nursing home coal mine as the breakthrough point,UDEC numerical simulation model is established to study the temporal and spatial evolution laws of the crack field,displacement field and stress field in the room and pillar method goaf under the influence of mining disturbance and static load,vehicle dynamic load and static load respectively,and to analyze the chain evolution process of the instability of the room and pillar method goaf under the influence of dynamic and static load.6)The disaster chain stages in the goaf is divided and grouting and filling technology in the room and pillar method goaf at the lower part of Baofu Road in the nursing home coal mine is established to cut off the disaster chain in the goaf,and verify the effect of chain breakage and disaster reduction by theoretical analysis,numerical simulation and field measurement.In conclusion,the instability mechanism and control technology of room-andpillar goaf under the influence of static and dynamic loads are studied from the perspective of catastrophe chain.Grouting filling in goaf has a good effect of chain scission and disaster reduction on the instability disaster control of room and pillar method goaf.It is an important part of the basic theoretical research on the catastrophic chain control of coal mine goaf instability,and has certain theoretical significance and broad application prospects.