Application Of Acoustic Emission On The Basis Of Studies Of Rock Failure Process

Underground metal mines continue to expand the scale of the exploitation ofresources, with increasing depth of the exploitation, the difficulty to monitoring the rooffall has greatly increased. So prediction must be taken to grasp the transmutation characterand rules of the roof fall, forecast the range, time and harm of the roof fall, and take theprecaution in time, to avoid the loss of the mining project and reduce the number of injures.According to the practical circumstance and the safety request of forecast, the acousticemission (AE) technique and its basic parameters are often used to inspect and forecast theroof fall. In this paper, the deformation, damage and acoustic emission of rock samples dueto uniaxial compression loading have been investigated with the method of a combinationof experimental investigation, theoretical analysis and numerical simulation.In accounting of the particular geographical and geological conditions, the experimentof rock samples was first carried out under uniaxial compression load, and at the meantime the AE signal at the process of compression was detected by AE instrument as well.The comparative investigation of the characteristics of deformation and AE wereconducted and the results are presented as followed: the characteristics of rock AE arecorrelated to the strength, joints, cracks, and the size and hardness of rock specimens. TheAE incident rate characteristics are not almost concordant with the AE energy rate.Based on experiment, the microscopic mechanism of rock rupture and theoreticalanalysis, two-parameter Weibull statistics model is specified in the evolution of rockdamage. And the two parameters are calibrated with the AE data of the experiment. Themodel has been modified rationally by discussing the empirical relation betweenparameters of the model and restricting pressure of rock and then a statistical damageconstitutive model applying to the condition of different confining pressures has beengiven out. The modified method for the model is followed by the analysis of the calibrationmodel. It is basic accordant between the modified theoretic model and the experimentresult, which verifies the rightness of the model.Finally, the process of damage, failure and AE of rocks under uniaxlial compression weresimulated by Particle Flow Code which is based on the theory of Discrete Element Methodaccording to variable strength and homogeneity. The simulation showed that with the decrease of the rock strength caused by the cracks in the rock sample model, the activity of AE becomesmore active and the nonlinear deformation of rock increases, brittleness grows gradually. Theresults of numerical simulations are consistent with the results of experimental tests. Then, toanalysis the damage process and the AE signal trend of uniform samples and containing weakstructure ones with amended model, attain the AE laws of fractured rock under the influence ofthe different angles.