Rockburst Nucleation Process And Characteristic Analysis Of Microseismic Informations In Deep-beried Tunnel

The construction of large number of large-scale Water Conservancy and Hydropower Engineering projects in China renders an accelerating trend in recent years.These projects confront the most common geological hazard is rockburst,which effect the project can not develop smoothly and make the machine damage and people injure.So far,the mechanism of rockburst is not very explicit,that the forecast of rockburst become passive.It is essential to study rockburst nucleation process,which decide the engineering success or not directly.Although the procrss of rockburst is transient and unexpect,however,there is also a period that forms the rockburst.This demonstrate the evolution of energy in rock.In this study,the hanjiang-to-weihe river water diversion project is used as the engineering background,and the 4th tunnel is selected as the monitoring object.Based on the acoustic emission characteristics of rock,a microseismic monitoring system is established to investigate the microseismic informations when tunnel is drivageing.The research results provides a guidance role in construction of the deep tunnel.The following major achievements are made in the paper:(1)To analyse the engineering geological environment in 4th tunnel,to acquire the rock sample from site,doing experiments of uniaxial compression test and cyclic loading test,acquired the mechanical parameters of granite.In terms of index of brittleness and energy to evaluate the rockburst tendency,the results showed that: the 4th tunnel have the strong rockburst tendency.(2)The study offers the mechanical basis to microseismic monitoring,the microseismic monitoring system is successfully established for 4th tunnel,Real-time monitoring and analyzing of the potential rockburst zone are realized.Including choose the suitable sensor and the layout of sensors,appropriate localization algorithm,classify and summarize the waveform character of different source of sound.Noise reduction that EMD and IMF reconstitution is apply to the noise corruoted signal,which laid the foundation for efficiently handing microseismic signals.(3)Analyse the spatial-temporal distribution regularity of rockburst and microseismic activities.To reveal the microseismic information in different type rockburst nucleation process.The method of seismic source parameters is analyzed,the mechanism of microseismic events is analyzed by considering the characteristic of magnitude-frequency and Es/Ep.The results indicates that: there are more large magnitude events in monitoring area,the microseismic activity is relatively high and the source belongs to fault slip type.the curve of magnitude-frequency distribution of rockburst high occurrence period is flat,b value is lesser,however,the b value is larger and curve is steep in quiet period;b value has the tendency of decrease with the increase of depth;surrounding rock failure mainly is shear failure and tensile failure partly.(4)The microseismic monitoring technique,numerical simulation and field practice method is discovered for rockburst prediction.To acquire the damage area of surrounding rock by microseismic informations processed,set up a model with intial damage area,this can show rockburst failure process and destroyed area more realistic.Meanwhile the factor of rockburst formation is preliminary studied.