Study On Mechanism And Prevention Of Roof Collapse Induced By Mine Earthquake

With the continuous increase in coal mining depth,a new type of roof collapse induced by mine tremors,different from conventional roof collapse,has emerged in rock burst mines.Rock burst is a typical dynamic disaster in mines,which usually causes roof and floor convergence,and rib spalling.Conventional roof collapse is usually the result of the roof falling under its own gravity,while the compound disaster of roof collapse induced by mine tremors is different from conventional roof collapse and typical rock burst,which often only cause the roof of the roadway to collapse during strong mine tremors.Currently,there is little research in this area.Therefore,this thesis uses statistical analysis,field measurements,theoretical analysis,numerical simulation,and other research methods to study the mechanism of the compound disaster of roof collapse induced by mine tremors and propose a prevention and control system for the compound disaster of roof collapse induced by mine tremors based on the research conclusions.The failure characteristics of conventional roof collapse,typical rock burst,and the compoundd disaster of roof collapse induced by mine tremors were compared and analyzed.A total of 165 cases of conventional roof collapse were classified,and the failure characteristics and main controlling factors of roof collapse were analyzed.The main influencing factors of the typical roof collapse induced by mine tremors were obtained through analysis,which included roof structure,roadway support strength,high stress field,and high-energy mine tremors.The dynamic response characteristics of roadway surrounding rock were revealed,and the influences of dynamic load strength,dynamic load position,cyclic loading,roof structure,and support methods on the roadway surrounding rock were studied.The following conclusions were drawn:(1)Under dynamic loading,the roadway roof will form a"Displacement arch"structure.When the dynamic load strength is small,the impact on the roadway is weak.When the dynamic load strength exceeds a certain value,it is easy to induce roof collapse.(2)When the dynamic load source occurs at the roadway floor,the impact on the roadway roof is small.When the dynamic load source is within a range of 40m from the roadway roof,it is easy to induce roof collapse.(3)After multiple cycles of 10~4J-level dynamic loading,the roof is prone to compound disasters.When the dynamic load strength is greater than 10~5J level,with the increase of dynamic load cycles,both the roof and bottom of the roadway will be damaged.(4)When the roadway is a half-coal rock roadway,no-roof coal roadway,or thin-roof coal roadway,the impact of dynamic loading on the roadway roof is small,while the thick-roof coal roadway is prone to roof collapse.(5)The"anchor rod+steel strip"support method has a good control effect on the compound disaster induced by mine tremors.(6)When the anchor rod spacing is small,the support effect is better.(7)The anchoring of the anchor cable in stable rock layers can improve the roadway support effect.The stress distribution of surrounding rock of rectangular roadway is analyzed.The results show that the occurrence of roof collapse induced by mine earthquake is influenced by tectonic stress and mine earthquake.The gradually deteriorated roof exceeds the ultimate breaking strength of the roof under the action of a strong mine earthquake,which results in dynamic development.The discriminant criterion of mine earthquake-induced roof collapse is established,and the prevention and control measures are put forward,as well as the multi-dimension roof control technology of"deep roof rupture-shallow load reduction-strengthening support".A monitoring and early warning method for compound disasters of roof collapse induced by mine tremors was proposed in a typical working face of Gaojiabao Coal Mine.Measures for prevention and control of the compound disaster,such as large-diameter borehole pressure relief,pre-split blasting of the roof,and coal body blasting pressure relief were also proposed and verified through on-site application,showing good prevention and control effects.There are 82 figures,21 tables and 103 references in this thesis.