| The feedback characteristics of loaded rock mass system plays an important decisive role in system catastrophe.In order to research the feedback characteristics of loaded rock mass system in the process of catastrophe preparing and triggering,in the view of system science,rock burst in underground stope system was taken as research object,the characteristics of loaed rock mass system was studied and hierarchy analysis model of system dynamic feedback was built.The feedback characteristics of underground stope system was analyzed layer by layer.Heterogeneity rock model was set up by MATLAB and finite difference software FLAC3D,which was used to study the influence of heterogeneity degree on the mechanical and deformation characteristics of rock model.The feedback characteristics of different strength element was studied through the comparison with the observation result of local lateral strain of cement mortar samples.The constraint degree criterion was put forward to judge the feedback type of strong-weak element system.Based on the storage and dissipation law of energy in the dynamic ejection rock-burst preparing and triggering process,variable section model was built to study the energy storage,transmit and dissipation law of energy storage body-deformation body system.The negative feedback criterion of underground stope system was studied in the view of energy.Research results show that1)System and factors are relative concepts,loaded rock（coal）system in underground stope can be divided into three sub-systems:loading coal（rock）mass system,energy storage body-deformation body system and tunnel-tunnel system,large-scale dynamic disasters in underground stope system result from sub-systems trigger layer by layer.2)The feedback types of different sub-systems are different.The feedback types of loading rock（coal）system is concerned with generalized stiffness coefficient;the preparing and triggering process of dynamic disasters can be simplified to the feedback adjustment process of energy storage body-deformation body system;the deformation quantity of unstable tunnel and the deformation quantity of stable tunnel constitute feedback structure,which influence each other through unbalanced force of stope system.3)The feedback type of strong-weak elements system in heterogeneous rock determines the mechanical properties and deformation characteristics of rock model.Energy and stress transfer coefficient between different strength elements will increase with the heterogeneity degree rising,which will result in the stress-strain curve fluctuation before peak load and the deformation characteristics after peak load changing from brittleness to ductility.The displacement mutation of strong-weak elements interface can be the negative feedback criterion of strong-weak elements system.4)The energy storage,transfer and dissipation law of energy storage body-deformation body can be described by variable section model.System will settle into negative feedback state when elastic strain energy relief rate is much larger than the energy like extension strain elastic energy and kinetic energy consumption rate,which will result in rock-burst.Suggestions of prevention and control dynamic disasters were put forward from perspective of system feedback.The research results above can offer reference ideas for dynamic disasters of underground stope system. |
