| Based on the National Natural Fund Project?No.51764013?,this paper studies the rock mechanics characteristics and surrounding rock stability of a mine.Firstly,the mechanical and acoustic emission characteristics of sandy slate,metamorphic sandstone and granite during uniaxial compression and Brazilian splitting failure are studied by using RMT-150 C test system and PC-II acoustic emission signal monitor.The mechanical properties,deformation and failure characteristics and evolution law of acoustic emission signals of three types of rocks under different loading modes are discussed respectively.Secondly,MATLAB software and G-P algorithm are used to process the collected AE data.Combined with fractal theory,the evolution law of correlation fractal dimension of AE parameters in different rock compression and tension processes is analyzed,and the micro-fracture mechanism of rock damage and failure under different loading modes is summarized.Finally,the factors affecting the stability of mine rock mass are analyzed theoretically,and six evaluation indexes are determined based on the results of field geological survey and laboratory tests.The comprehensive evaluation model of the stability of surrounding rock mass of the mine is constructed by using the unascertained measurement theory and an objective and scientific evaluation is made.Through the above three aspects of research,the following conclusions are drawn:?1?Under uniaxial compression,the uniaxial compressive strength and material stiffness of the sandy slate are the largest,the metamorphic sandstone is the second,and the granite is the smallest.Before the instability failure,the acoustic emission signals of the three types of rocks increase sharply,and most of them reach the maximum at the time of failure.The breaking points of the acoustic emission signals of sandy slate,metamorphic sandstone and granite samples are near 0.95,0.93 and 0.84 of the peak stress,respectively.The abrupt change point of the sharp increase of acoustic emission signal can be regarded as the precursor feature of rock compression and instability failure in the middle 417 section of mining area..?2?Under Brazilian splitting conditions,the tensile strength of sandy slate,metamorphic sandstone and granite is the largest,followed by metamorphic sandstone and granite.The acoustic emission signals of the three types of rock fracturing process have some similarities.During the whole test process,the acoustic emission ringing counts and energy are at a low level and increase with the increase of stress.During the plastic yield and failure stages,the acoustic emission signals are active,and the ringing counts and energy increase sharply to the maximum in the failure stage,which can be used as a precursor of the tensile instability failure of the 417 middle section of the mining area.?3?The acoustic emission ringing counts and energy parameters of sandy slate,metamorphic sandstone and granite specimens under compression and Brazilian splitting failure have significant fractal characteristics.Although the fluctuation of fractal dimension of AE in compression and fracturing process of three kinds of rock specimens is quite different,most of them undergo a continuous decline from maximum to minimum fractal dimension before failure.This change pattern can be used as a signal of instability failure of rock in 417 section of mining area.?4?The comprehensive evaluation model of surrounding rock stability in 417 section of mining area is constructed by using unascertained measurement theory.The subjective and objective weights obtained by G1 method and entropy method are optimized by difference coefficient method.The comprehensive unascertained measure of multi-index is determined.Finally,the stability grade of surrounding rock in 417 section of mining area is calculated and analyzed to be grade ??basic stability?. |
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