Study On Microseismic Signal Characteristics And Effect Evaluation Of Grouting Reinforcement Of Collapse Column

The collapse column of the floor in the coal formation will directly affect the safety and economic benefits of coal mine production.Grouting and reinforcement treatment of the floor collapse column is an effective means to ensure the safe recovery of the coal seam remining face of the collapse column.It is the development direction of coal mine safety production to use the microseismic monitoring system to monitor the whole cycle of grouting reinforcement in real time and evaluate the grouting reinforcement effect of collaps column.Therefore,based on the viscoelastic wave equation,a simplified collapse column geological model is established,combined with the microseismic signal of the engineering site,the signal characteristics of typical grouting microseismic signal at different grouting stages and different grouting locations are studied,and the grouting diffusion range of each grouting stage is determined by locating the on-site grouting microseismic signal,so as to complete the preliminary evaluation of the grouting effect of the collapse column,and finally verify the grouting effect based on the results of drilling and network parallel electrical monitoring.The main research results of the thesis are as follows:(1)The viscoelastic geological model of the collapse column was established and the grouting process of different grouting positions was simulated,and the amplitude,main frequency,duration,time frequency and other signal characteristics of the grouting microseismic signal at different stages were analyzed by using the methods of frequency dispersion analysis,time-frequency analysis,AIC and energy ratio,and the results showed that the internal medium of the single hole entering the key layer of the collapse column was relatively broken,the internal medium Q value of the collapse column was small,and the energy amplitude and main frequency attenuation characteristics of the microseismic signal were strong.With the progress of grouting work,the Q value of the medium inside the collapse column gradually increased,and the attenuation characteristics of microseismic signal propagation gradually weakened when the single hole entered the middle of the key layer of the collapse column and the single hole penetrated the key layer of the collapse column at 10 m.The distance from the microseismic source to the sensor is inversely proportional to the magnitude of the microseismic signal and proportional to the signal duration.(2)The background signal,random signal(electrical interference signal,mechanical interference signal)and typical grouting microseismic signal collected in three grouting stages of single hole entering the key layer of collapse column 10 m,single hole entering the middle of the key layer of collapse column,and single hole penetrating the key layer of collapse column 10 m in the engineering site are analyzed respectively.The signal characteristics such as amplitude,main frequency and duration are analyzed,and the grouting microseismic signals of each stage are determined according to the signal difference characteristics of different grouting stages,which provides the basis for determining the slurry diffusion range of each grouting stage by microseismic positioning method.(3)Through the microseismic location of borehole grouting signal in different grouting stages,the diffusion range of grouting grout in the key stratum area of the collapse column is determined.Combined with the diffusion range of grouting grout between different holes in three grouting stages,the preliminary evaluation of the grouting effect at the key stratum of the collapse column is realized.The on-site data processing results show that:(1)When a single hole enters the key layer of the collapse column at 10 m,the grout diffuses to the interior of the collapse column along the shallow part of the borehole,and the microseismic location points are mainly concentrated in the range of-500m～-530m;(2)In the grouting stage when the single hole enters the middle of the key layer of the collapse column,the grouting area is mainly in the middle of the key stratum of the collapse column.The grout diffuses far and covers most of the shallow middle area of the collapse column,and the microseismic location points are basically in the range of-540m～-580m;(3)The grouting slurry gradually diffuses horizontally to the deep area of the key stratum in the 10 m grouting stage of the single hole through the key layer of the collapse column.The grouting area is mainly deep in the key stratum of the collapse column,and the microseismic location points are basically in the range of-560m～-610 m.(4)Combined with the network parallel electrical real-time monitoring and drilling methods,the results of the grouting effect of the key layer of the microseismic monitoring collapse column were verified,and the results showed that,on the whole,with the continuous grouting work,the low-resistance water-rich area in the key layer of the collapse column grouting gradually changed from large to small and finally disappeared,indicating that the grouting effect of the key layer of the collapse column reached the expected.After the completion of the grouting work at the key layer of the collapse column,the drilling water injection test was carried out,and the seepage resistance strength of the collapse column after grouting reinforcement was not less than 1.5 times the hydrostatic pressure of the Olympian gray water,which met the technical requirements of the grouting treatment of the bottom plate of the collapse column.The verification results prove the effectiveness of the collapse column grouting reinforcement evaluation method based on microseismic monitoring.