Study On Feature Identification Of Sub-instability Stage Of Coal Rock Deformation

The sub-instability stage is an important stage in the process of coal rock deformation and damage,and it can provide a reliable theoretical basis for the prediction and warning of impact ground pressure hazards due to coal rock deformation by using the sub-instability stage as a short-range prediction stage of coal rock damage.To identify the characteristics of the sub-instability stage of coal rock,the thesis adopts the digital speckle correlation method and acoustic emission technology as the monitoring means to study the characteristics of the sub-instability stage of coal rock deformation under uniaxial compression loading,analyse the characteristics of the deformation evolution stage of coal rock and the acoustic emission characteristics of the deformation evolution stage,obtain the deformation field parameters and acoustic emission parameters,and combine with the proposed sub-instability stage comprehensive index identification method to identify the sub-instability stage of coal rock respectively.The sub-instability stages were identified by combining the proposed method of identifying sub-instability stages with the proposed comprehensive index method.In addition,by analysing the microseismic data in the field,the sub-instability identification method is further introduced into the microseismic monitoring and early warning system of coal mines,which is of great practical significance for the effective prevention and control of impact ground pressure hazards.In the study of the evolutionary characteristics of coal rock deformation stages,the evolutionary characteristics of coal rock deformation are investigated by conducting coal rock uniaxial compression tests combined with digital scattering correlation methods.Based on the study of the evolution process of coal rock deformation field,a non-uniformity index is proposed to classify the coal rock deformation stages;from the perspective of deformation evolution,the migration phenomena and characteristics of the localised zone,the spatial non-uniform sliding characteristics of the localised zone,the fluctuation evolution characteristics of energy accumulation and release,the crack expansion and intersection characteristics of the sub-instability stage,the epicentre migration,the sliding "convergence" characteristics,and the sub-instability stage.The similarities and differences of coal rock deformation characteristics are summarised,including the characteristics of localised zone jumping,energy fluctuation evolution,sliding convergence and deformation wave propagation.The study of the deformation and damage mechanisms of coal rocksIn the study of the acoustic emission characteristics of coal rock deformation,acoustic emission is used as a monitoring tool to study the acoustic emission characteristics of coal rock deformation.Through the study of the spatial and temporal parameters of acoustic emission,a full waveform extraction method and spatial aggregation parameters of acoustic emission were proposed,and a program was written to obtain the characteristics that the distribution trend of acoustic emission localisation points in the deformation evolution stage of coal rock is consistent with the spatial and temporal evolution of the localisation zone.From the perspective of deformation evolution,the characteristics of acoustic emission in the deformation stage of coal rocks are analysed,and the characteristic laws of pre-peak surge of acoustic emission event rate,spatial aggregation of acoustic emission,and solution of acoustic emission source mechanism are summarised.In terms of identifying the characteristics of the sub-instability phase of coal rocks,firstly,according to the characteristics of localisation of coal rock deformation,the plastic gradient theory is used to establish a mechanical model of the sub-instability phase of coal rocks,and the factors influencing the sub-instability of coal rocks are discussed.The equivalent stiffness of the localisation zone is related to the localisation zone.A system for identifying the acoustic emission indicators of the sub-instability phase of coal rock deformation was established,and the sub-instability phase of coal rock was identified by the integrated indicators,and good results were obtained.In the field application of coal rock sub-instability identification,the microseismic events collected from the working face of a coal mine were classified and extracted according to the top plate,bottom plate and coal seam,and the time-frequency domain parameters,temporal and spatial intensity parameters and rupture types of microseismic monitoring data were analysed,and discriminated by the proposed comprehensive index identification method of sub-instability phase,which provides reference for mine disaster prevention and control,and this method was introduced into the coal mine microseismic monitoring and The method is then introduced into the mine microseismic monitoring and early warning system to achieve real-time monitoring and prediction of mine microseismic.