Study On Deformation Failure Law And Stability Of Roadway Roof In Mine Rock Contact Zone

When the roadway passes through the contact zone of the rock,the stress balance state of the rock mass is disturbed,causing the stress field to redistribute.Due to the difference in the distribution characteristics of the stress field of different rock masses,the deformation of the rock mass on both sides of the contact zone are uncoordinated,resulting in deformation and even instability of the roof of the roadway.Therefore,it is the basis for ensuring the safety and stability of the roadway to study the distribution characteristics of the stress field in the roadway roof of rock contact zone and to master its deformation and failure law.Relying on the National Natural Science Foundation project "Research on the mechanism and control principle of non-coordinated deformation and failure of contact roadway(51574183)",a systematic study was carried out on the deformation and failure regularity and stability evaluation of the roadway roof in the rock contact zone by theoretical analysis,numerical simulation,laboratory test and field test.The uniaxial compression acoustic emission test of composite rock mass specimens in ore-rock contact zone was carried out,and the basic mechanical parameters were obtained.The influence of similar material strength ratio and volume ratio on the deformation and failure of composite rock specimens was analyzed.Based on the failure condition of composite rock mass,,the crack length expansion factor is defined and verified by the change of the acoustic emission event count.Three forms of deformation and failure of the composite rock specimen are characterized.The relationship between radial and cyclic stress of composite rock specimens is constructed by using cylindrical coordinate equilibrium differential equation with axisymmetric problem,and the relationship between the stress variation of the contact surface and the ratio of elastic modulus and the contact surface angle are calculated.The results show that the radial stress and the cyclic stress of the composite rock specimens decrease with the increase of the elastic modulus ratio,and decrease with the increase of the contact surface angle,which provides the basis for the main influencing factors of the roof deformation failure of the contacting Roadway.By using the numerical simulation method,the influences of rock strength difference,contact surface angle and buried depth on rock stress distribution,roof settlement deformation and plastic zone distribution of surrounding rock are analyzed,and it is shown that the settlement deformation along the roadway of the mine rock contact zone has obvious regional characteristics.Based on the similarity theory,the physical similarity simulation test model of the contact zone of Daye iron ore is constructed,the monitoring scheme of the strain displacement meter along the roadway direction and the contact surface of the rock is designed,and the excavation of the adjacent roadway is increased to the extent of the uneven settlement of the rock mass on both sides of the contact belt roadway.On the spot monitoring of the contact zone of Daye iron ore rock,it is found that the roof settlement and settlement rate of the marble side of the contact zone are greater than that of the iron ore side roof.The consistency of similar simulation and field monitoring test results proves the reliability of the settlement deformation law of the roadway roof in the rock contact zone.The basic types and characteristics of the roof deformation and failure of the roadway in the contact zone of the mine are summarized by field investigation and statistical analysis.Combined with the phenomenon of stress concentration and transfer of rock mass after excavation,based on the theory of shear stress strength,the evolution mechanism of shear failure of rock mass in the roadway of rock contact zone is expounded.The mechanical model of rock beam with roadway roof in the rock contact zone is constructed,and the expression of roof settlement of the contact zone roadway is deduced.The research reveals that the deformation and failure of roadway roof in the rock contact zone is the result of the joint action of shear stress and compressive stress,which provides theoretical explanation for the deformation and failure law of roadway roof in the rock contact zone.Aiming at the uncertainty of roadway stability evaluation of the contact zone,based on the unascertained measure theory,the evaluation index of the roadway stability of the contact zone is graded.The single index measure function is established,and the unascertained evaluation model of the contact roadway stability is constructed.Taking the four contact belt roadways in the Jianlinshan of Daye Iron Mine as samples,the stability evaluation was carried out by using the constructed model,and the evaluation results were in good agreement with the mine.The unascertained measure evaluation model has a good applicability to the stability evaluation of the rock contact roadway,and provides a new idea for the stability evaluation of the mine rock contact zone.The mechanical characteristics of rock contact zone composite rock specimen,the settlement and deformation law of roadway roof and the evaluation of roadway stability based on unascertained measure theory are used to reveal the law of deformation and failure of roadway roof of rock contact zone,and the stability evaluation method suitable for mine rock contact roadway is proposed.The control and treatment of roof stability provide theoretical support and engineering practice guidance.