| With the rapid development of the economy in our country,the demand for mineral resources has increased gradually.The improvement of the production capacity,combining with the complex geological conditions,makes mines in China suffer from frequent geological disasters,especially water disasters,whose mechanism are becoming more complex.How to interpret the mechanical mechanism and evolution law of microcracks inner rock masses is an important issue.The geological environment of rock mass is complex,which makes it very difficult to analyze the stability of rock mass theoretically and accurately.Thus,field monitoring methods are employed.The formation of a seepage channel in rock mass is usually associated with fractures(microseismicity).By using induced microseismicity,this study aims to found a complete and exact routine to reveal the initiation,propagation and occurrence of water inrush hazards and their mechanisms.The main contents are summarized as follows:(1)This study realized the digital filtering of the original signal,automatic wave picking,3D seismic source locating,source parameters calculation,moment tensor inversion,radiation patterns,fault plane solution and the velocity field tomography.The visualization of the events evolution process,source mechanism,radiation pattern,colored map of source parameters,3D rose diagram,etc.,was implemented.Pencil break test was conducted to verify the arriving-time picking and event positioning code,which provided a guarantee for the reliability of data analysis results.(2)The theory of seismic moment tensor inversion and the far-field P-wave radiation patterns in acoustic emission and microseismicity were discussed and derived;P-wave energy at the source was derived based on the radiation pattern;a variety of ray-tracing algorithm and velocity field tomography were implemented;a method to evaluate the sensitivity of the sensor array was proposed.These codes were applied and verified in the laboratory test.The damage evolution law of sandstone under uniaxial compression was analyzed,the "weak zone" and the formation mechanism of the macro-fractures were obtained.Finally,development of the velocity field anomaly areas and the correlation between the macro-fractures and the anomaly areas were analyzed using P wave seismic tomography.(3)Based on the theory of microseismic monitoring and moment tensor inversion,the analysis routine of the formation process and mechanism of seepage channel were established.The spatiotemporal evolution laws of event density,as well as source parameters,including moment magnitude,source radius,etc.,were analyzed,so as to reveal the initiation,propagation and coalescence of seepage channels.The formation of local seepage channels can be classified into four types:shear-tension-shear(STS),strong shear(SS),weak shear(WS)and tensile(T).The orientation information of main fracture surface of seepage channel was then fitted and obtained.Finally,two distinct water inrush paths were interpreted.(4)Based on the spatiotemporal evolution laws of the microseismic events and moment tensors,the main water recharge sources,the water inrush areas and the mechanical process of the seepage channel were obtained.The bond network diagram was used to analyze the hydraulic connection between microcracks.The depth search algorithm was used to obtain the shortest seepage path between the recharge area and the inrush area.By using 3D rose diagram and stereographic projection,the direction of the fracture surface is determined,and the main direction of the true fracture surface is obtained.Accordingly,the 3D fracture network based on the moment tensor inversion was generated.The octree algorithm was used to establish the calculation model,in which the microcracks were embedded.Then,stress field in the seepage areas was calculated. |
