Theoretical And Experimental Study On Parameter Optimization Of Active Sources In Seismic Wave CT Inversion

In order to solve the problems of high cost and great influence of production in active source seismic wave CT inversion and uncontrollable inversion period and accuracy of target area in passive source seismic wave CT inversion,the active source passive source seismic wave integrated inversion technology is constructed by combining active source and passive source,so as to realize low cost,low production interference,inversion period and accuracy Controlled seismic wave CT inversion.In order to construct the integrated inversion technology of active source and passive source,it is necessary to add active source on the basis of the existing passive source to realize the effective coverage of the target area by the vibration wave ray.Theoretically,the effective coverage of the target area by the vibration wave ray is controlled by the number and location of the active sources.Therefore,it is necessary to propose an optimization method to determine the optimal number of active sources and location parameters in the integrated inversion.Based on the theory of seismic wave CT inversion,this paper presents an optimization method for the number and location of active sources.This method includes two evaluation indexes: accuracy index and stability index.Among them,the lower the accuracy index,the higher the accuracy of inversion results;the smaller the stability index,the more stable the inversion results.Because the accuracy index and stability index can not get the minimum value at the same time,a multi-objective mathematical model is constructed to solve the optimal solution of them.In the process of solution,the genetic algorithm is used to reduce the complexity of solution to solve the problem of huge understanding space,so that the solution converges quickly.The modular optimization program is programmed with MATLAB,and the numerical simulation of different schemes is carried out.The results show that:(1)the ray coverage density has nothing to do with the accuracy of inversion;(2)after optimization,the accuracy index and stability index of the target area are greatly reduced,the inversion wave velocity value approaches the theoretical value,and the inversion wave velocity variance is significantly reduced;(3)when multiple areas are optimized at the same time,the optimization effect of each area is positively related to its weight.The acoustic emission monitoring system with active ultrasonic testing function and the electro-hydraulic servo press system are used to optimize the parameters of the active source.During the test,the ultrasonic test data and acoustic emission data of large-scale samples under local load are collected,and the active source parameters are optimized in stages.It is found that the optimized inversion results are more in line with the law of stress transfer and stress distribution,and the connectivity of low velocity zone in fault zone or weakening zone is enhanced.In view of the problem that the current seismic wave CT inversion technology can not continuously monitor and warn the rockburst disaster,an optimization algorithm is proposed based on the characteristics of active source and passive source seismic wave CT inversion and warning.The algorithm shortens the inversion period,further improves the inversion reliability,and realizes the continuous prediction of rockburst disaster Police.There are 58 figures,18 tables and 70 references in this paper.