Microseismic Monitoring And Numerical Simulation Research On Floor Failure Characteristics Of Normal Faults Affected By Coal Seam Mining

With the continuous increase of coal mining depth,the water pressure and ground pressure on the floor are getting bigger and bigger,and the harm of water inrush from the coal floor is increasing day by day.The fault interrupts the integrity of the continuous distribution of rock formations.The stress distribution in the area where it is located is abnormal,and the mining effect is very obvious,especially the normal fault area,which is susceptible to recovery activities that lead to fault activation and floor water inrush disasters.Therefore,how to effectively prevent and control water inrush hazards caused by floor faults is the key research work of the coal mine water control department,especially when there are unproven concealed small and medium-sized faults in the working face,and also exist in the process of pushing through these concealed faults in the working face.The possibility of a water inrush accident.Based on thi s kind of research background,this paper takes the 1612 A working face of Zhangji coal mine as the basis,using theoretical analysis,numerical simulation and microseismic monitoring and other technical means,and takes the normal faults that have a greater impact on the working face as the research object,starting from the 1612A working face.Based on the analysis of the evolution law of the floor disturbance stress field in the fault-affected area,combined with the analysis of the microseismic activity in the fault area of the working face,the floor failure characteristics and the law of microseismic activity in the fault-influenced area caused by coal seam mining are systematically studied.The concealed structure of has been identified and analyzed,and the following work has been mainly carried out:First,analyze the nature of fault activation and its main influencing factors,including fault type,dip,drop,and mine pressure.Secondly,using numerical simulation methods,the influence range of floor stress disturbance and stress field evolution characteristics of the main normal faults in the 1612A working face under the fault-affected area under the mining action are studied,and the working face floor during the normal fault hanging wall mining process is analyzed.The stress evolution law is compared with the normal faults F1611A76,F1611A77 and F1611A80 under different conditions of the floor fault stress evolution law,and the effect range of the floor stress disturbance in the main normal fault-affected area of the 1612A working face is obtained.Then,according to the actual situation of Zhangji Coal Mine,a microseismic monitoring system for the 1612A working face was built.The microseismic monitoring results showed that the microseismic activity of the working face was closely related to mining activities.Microseismic events in the working face are mainly distributed in two regions(zone Ⅰ and zoneⅡ),and the spatial distribution of microseismic events in the two regions is similar.The moment and magnitude distribution curves of microseismic events in Zone Ⅰ and Zone Ⅱ contain two peaks respectively,and the peak intervals of the moment and magnitude distribution curves in the two regions have an overlapping relationship.Further detailed statistical analysis shows that there are also two dense areas of microseismic events in the working face floor(Area A and Area B),and the A and B areas overlap with the C2 and Ⅱ areas.Compared with the roof microseismic event,the floor microseismic event The energy released by the event is small,and the distribution horizon is also small.At the same time,combined with the statistical analysis of the floor damage depth obtained from the microseismic monitoring,a line graph of the water inrush coefficient value of the working face floor based on the microseismic monitoring results was drawn,and the water inrush risk of the working face floor was compared and analyzed.Finally,the distribution law of rock microseismic events in the stope and the influence of the mining progress of the working face on the "temporal and spatial strength" characteristics of the microseismic event are analyzed,and the hidden structure in the working face is identified.At the same time,combined with numerical simulation and channel wave exploration technology,the evolution characteristics of the stress field of the surrounding rock in the concealed structure area are analyzed,the stress concentration phenomenon of the isolated island working face with broken zones at both ends is explained,and the number of microseismic events and the energy-intensive characteristics of the isolated island working face are explained,Verified the existence of the hidden structure of the 1612A working face.A small faulted structural zone and a concealed normal fault were exposed when the working face was recovered to Zone Ⅱ.The existence of the concealed structure of the working face was proved on the spot,and the concealed structure based on "microseismic identification+digital model inversion+physical survey verification" was further verified.The predictive recognition analysis method is feasible and accurate.