Mechanical Behavior And Electromagnetic Radiation Response Characteristics Of Water Bearing Sandstone Destruction Under Load

Electromagnetic radiation technology as an important means of coal and rock dynamic disaster monitoring and early warning has been widely studied by scholars,but at present,the research on the electromagnetic radiation effect of rock damage under load rarely involves the water bearing rock.The hydraulic measures such as rock mass water injection are widely used in the prevention and control of rockburst in coal mines.It changes the original stress state of rock mass and has a significant impact on the microstructure and composition of rock.Therefore,it is of great significance to study the mechanical behavior of water bearing rock under load and the characteristics of electromagnetic radiation signal for the prevention,monitoring and early warning of dynamic disasters such as mine rockburst.In addition,it is also related to the stability monitoring of water bearing rock mass in underground engineering and the early warning of other related geological disasters.In this paper,the sandstone samples with different water content(deionized water)are prepared,and the electromagnetic radiation experiments of the damage under uniaxial compression are carried out.The mechanical properties and energy evolution mechanism of sandstone with different water content are studied.The time-frequency and nonlinear characteristics of electromagnetic radiation signal are analyzed.The micro fracture mode is observed,and the mechanism of the influence of water on the electromagnetic radiation signal is explored.Finally,the damage evolution model of water bearing sandstone based on electromagnetic radiation is established.The main conclusions are as follows:(1)With the increase of water content,the uniaxial compressive strength and elastic modulus of sandstone decrease gradually,the peak strain increases,the input strain energy before the peak decreases gradually,and the proportion of dissipation energy increases.The yield characteristic of the specimen with high moisture content is more obvious in the stage of plastic deformation,and the dissipation energy increases significantly,and its failure is gradual.The more work the post peak press continues to do,the more fully developed crack and the more complex fracture morphology will be in the final failure.(2)The time sequence change of electromagnetic radiation energy in the process of sandstone loading is in good agreement with the deformation and fracture,especially in the later stage of loading,with a large amount of energy dissipation electromagnetic radiation energy appears obvious sudden increase.With the increase of water content,the electromagnetic radiation energy released gradually decreases.The main frequency of electromagnetic radiation is distributed between 0-200 kHz,mainly in the lower frequency range of 0-80 kHz.With the increase of water content,the high frequency signal decreases and the low frequency signal increases.(3)The electromagnetic radiation signal in the process of sandstone loading has obvious multifractal characteristics.With the increase of water content,the difference of signal distribution is smaller,and the small-scale signal is gradually dominant,and the multifractal characteristics are weakened.The multifractal parameters ?(6 sudden increase and ?1)sudden drop can be regarded as the precursory information of rock failure,and the precursory characteristics of samples with high water content are more obvious.(4)Water has a significant effect on the micro fracture mode of sandstone.Sandstone with higher water content is more prone to intergranular fracture than transgranular fracture,and the mode is more single.This may be an important micro reason for the weakening of electromagnetic radiation of water bearing sandstone,and also provides an explanation for the reduction of high frequency electromagnetic radiation signal and the weakening of multifractal characteristics.Moreover,the decrease of water on the macroscopic mechanical strength and fracture mechanical properties of sandstone will also weaken the electromagnetic radiation signal produced by piezoelectric effect and charge separation.There are 26 pictures,1 table and 88 references in this paper.