Research On The Characteristics Of Microseismic Activity And Surrounding Rock Stability During Tunnel Excavation In Jinfeng Gold Mine, Southwest Guizho

Mining geological conditions in southwest Guizhou area are complex,and deep roadway surrounding rock stability control and disaster warning have become important problems in mine safety production in this area.This paper takes Qianxinan Jinfeng Gold Mine as the engineering background,in view of the roof and patch phenomenon during roadway excavation,using a combination of field investigation,theoretical analysis,microseismic monitoring and simulation test,the microseismic signal characteristics and space-time evolution of microseismic events during 30 E horizontal roadway excavation are studied.The main research conclusions are as follows:(1)The deformation and failure characteristics of roadway are as follows: large convergence displacement on both sides and asymmetric deformation failure.The roof arch bends and cracks.The factors affecting roadway instability include: section size,surrounding rock lithology,ground stress and geological structure,excavation disturbance and support effect.(2)Install the IMS microseismic monitoring system.Using the manual percussion rock wall test method,the P wave speed of 5050 m/s is selected as the optimal wave speed,and the system error is less than 10 m to meet the positioning accuracy requirements of practical engineering applications.(3)For the mode aliasing effect of traditional Hilbert-Huang transformation,the combined set empirical mode decomposition and Hilbert transform constitute an improved HHT method.Five parameters were extracted,including the skewness,criness,LZ complexity,Hilbert marginal spectral energy,fractal dimension of two signals,and feature dimension reduction was performed by the Laplacian-score algorithm.Finally,the GA-SVM model was identified,and the identification accuracy reached 95%.(4)The spatiotemporal distribution characteristics of microseismic events and the evolution law of focus are closely related to the construction activity intensity,which belong to the instant microseismic.When the construction strength is weak,the number of microseismic events is small,the multifractal spectral parameters and the source parameters change smoothly.After the increase of construction strength,the number of microseismic events surges,the cumulative visual volume,energy index and Schmidt number increase.When the surrounding rock deformation and damage is serious,the microseismic events are mainly large seismic magnitude,the cumulative apparent volume and energy index growth rate are significantly increased,and the Schmidt number is rapidly reduced,the risk of rock mass instability is increased.After the construction strength is reduced and the support strength of the surrounding rock is improved,the microseismic activity is weakened,the stress concentration shifts to the depth of the rock mass,and the surrounding rock enters the slow deformation stage.