Study on the fracture and the law of temporal-spatial evolution of acoustic emission of gypsum and sandstone specimens

By means of acoustic emission ( AE) method,the authors experimentally tested the gypsum and sandstone specimens under uniaxial compression,the deformation curve of load-axis and AE parameters in the process of fracture of two specimens were obtained,the rupture of the specimen was observed,and the temporal and spatial evolution of AE and the multifractal characteristics of the waveform were analyzed. The results show that the uniaxial compressive strength of sandstone specimen is more than 7 times of that of gypsum specimen. Due to the change of lithology,the macroscopic fracture morphology of gypsum and sandstone specimens changes from “ X” to inverted “ Y”. The AE counts of the two specimens are consistent with the stress variation,but the maximum value of pulsing counts of sand- stone specimen is much larger than that of gypsum specimen. The waveform of the two specimens during the fracture process has multifractal characteristics,during the fracture process,the multifractal spectrum width is smaller than that of before fracturing,the before fracturing is smaller than that of after fracturing,and the of sandstone specimen at each stage is smaller than that of at the corresponding stage of gypsum specimen. It is shown that the energy of the two spec- imens during fracture is greater than that before fracturing,and the energy before fracturing is greater than that after fracturing. Through the comparative analysis,the authors can understand the fracture process of gypsum more deeply. Gypsum samples have similar fracture like sandstone,but as the forms are different,under the same conditions,the en- ergy produced by fracturing of gypsum is less than that of sandstone. The study lays a theoretical foundation for the prevention and control of rockburst in gypsum mine.