Chaotic Inversion Of Deep Three-dimensional Crustal Stress Field And Its Application

The ongoing mining production and increasing productivity of many mining enterprises have led to their deep mining activities. Deep mining environment, characterized by huge crustal stress, high ground temperature, enormous karst pressure and large disturbance, contributes to tremendous alteration of mining activities and rock mechanics. Frequent crustal stress activities, in particular, are most likely to promote the development of disasters caused by such factors as roof falling, tunnel deformation, et al. In most cases, disasters due to high crustal stress inflict damage with more severity than those caused by ground temperature and karst pressure. It is therefore a very important and worthwhile issue to figure out ways of getting rid of this malady, thus, realizing safe and efficient mining.This paper, in light of the program of Spatial Information Modelling and Dynamic Monitoring of Goab by3D Laser Scanning, a key program under the auspices of the Twelfth Five-Year Plan of Science and Technology of China, and the program of Measurement and Distribution Study of3D Deep Mining Crustal Stress, presents a study concerning measurement of3D crustal stress in Fankou lead-and-zinc mine and corresponding study of chaotic numerical inversion concerning the said crustal stress field. During this study, field experiment, theoretical analysis, numerical simulation and programming were applied, and so were mathematical tools including SURPAC, FLAC3D and Matlab, while a study of figuring out the optimal mining parameters was presented. The main research contents and results are as follows:1) An investigation of deep mining engineering and geological structure was made, based on which, Borehole overcoring method was used to measure the stress of rock samples derived from the-550m and the-650m level. The dual-axis calibration experiment was then conducted upon the extracted cores to get the coefficients of release strain and rock elasticity. The measured data was then processed to figure out the distribution and variation law of deep mining crustal stress.2) Factors influencing the crustal stress field were analyzed from the perspective of its formation, based upon which the main load form used in crustal stress field inversion was settled. A statistical data analysis concerning crustal stress field gathered during the past five years was made. This analysis helped with the numerical simulation revealing the law of inversion load changed with depth, leading to the formation of nonlinear loading functions. The FISH language was then used to programing the nonlinear loading functions.3) SURPAC was used in solid modelling of the deep mining environment, which included the stratum, fault and ore body. The SURPAC-FLAC3D technique developed by our research team was then used to build the numerical model of crustal stress filed inversion calculation. A physical mechanical experiment was then conducted to figure out data concerning the physical mechanical property of the rock. A field investigation was made concerning the geological structure of deep mining environment, based on which the Hoek-Brown law was applied to figure out rock strength parameters.4) A chaotic searching theory based method for crustal stress field inversion was proposed. Typical combination of inversion data was made, with which trial calculation of initial crustal stress field was done. The inversion parameter and crustal stress trial calculation value was paired together to build a neural network model for deterministic calculation. A target function was built for the best approximation between the neural network output and the measured crustal stress. The chaotic loading wave theory was used to search for the optimal inversion parameter. The said parameter was then used for numerical simulation, which contributed to the initial crustal stress field. Deep mining activity was then simulated, contributing to the distribution and variation law of existing crustal stress field.5) Based on the result of crustal stress field and the deep mining situation, subject of deep mining structure optimization was settled. Elastic mechanics theory was used to analyze mining stress distribution, which lead to the law of roof stability variation with structural parameters alteration. An initial plan concerning structural parameters was proposed. Taking into account safety and economic factors, the numerical analysis and TOPSIS method were used to decide the final optimal deep mining structural parameters.The study and its finding is conducive to the fully command of crustal stress field distribution and variation of deep mining environment in the Fankou mine. Scientific proof could be derived from this study for location of deep mining environment, mining engineering and parameter optimization, demonstrating the very important theoretical and practical significance of this study.