Floor failure mechanical behavior and partition characteristics under the disturbance of voussoir beam instability in deep coal mining

Floor failure becomes intensified under the additional property of strong disturbance in deep coal mining, which easily connects hydraulic fractured zone and induces confined aquifer water inrush disasters. Therefore,it can provide an important theoretical basis for realizing strata control in coal mines by the research on floor failure mechani- cal behavior under the disturbance of voussoir beam instability. According to the elastic-plastic mechanics theory,the dynamic load source characteristic of floor failure under the disturbance of voussoir beam instability in deep coal mining was analyzed. Mechanical behavior of compression-shear failure and unloading failure under the disturbance of voussoir beam instability were studied based on pressure arch theory and damage mechanics. The discrete numerical software was applied to calculate the floor stress change and deformation and failure behavior under the disturbance of voussoir beam instability in different mining depths. Combined with the complete stress-strain relationship of mining- induced mechanical test, strong disturbance failure partitions characteristics of floor in deep coal mining were ob- tained. Then it carried out verifications by using the mi-croseismic monitoring data of field measurement in deep coal mining. The results show that the stress increases at the coal rib and touching gangues area of the beam end after the main roof beam instability,and plastic yielding zone and touching gangues are formed at the floor,and unloading fail- ure zone is shaped in the middle of them,which appears as the pressure arch shape. With mining depth increasing,the incremental compression stress of floor plastic yielding zone,touching gangues and unloading rebounding stress of un- loading failure zone increase grad-ually,which cause the largest deformation of floor rock mass increase approximate linearly with the mining depth less than 700 m,but increase nonlinearly and change suddenly when the mining depth is more than 700 m. High confining pressure of deep coal mining leads to peak compression stress and unloading reboun- ding stress raises nonlinearly,which results in the failure of disturbance rock mass changing from the brittleness of shallow mining to the ductility of deep mining,then it brings about the expansion of partitions range of strong disturb- ance failure and the growth of deformation failure depth. The nonlinearly failure behavior of floor under the strong dis- turbance is most prominent in the shallow part in deep coal mining.