石膏和砂岩试样损伤破裂及声发射时空演化规律研究

通过对石膏和砂岩试样进行单轴压缩声发射试验,获取两种试样破裂全过程中的载荷-轴向变形曲线及声发射参数,观察试样破裂失稳情况,分析破裂过程中的声发射时空演化规律和波形的多重分形特征。研究结果表明:砂岩试样的单轴抗压强度是石膏试样的7倍多;由于岩性的变化,石膏和砂岩试样的破裂宏观形态由"X"型变化到倒"Y"型;两种试样声发射脉冲计数与应力变化规律比较一致,但是砂岩试样脉冲计数的最大值远远大于石膏试样;两种试样三维空间定位点分布与各自破裂宏观形态是一致的,但出现的时间以及分布位置是不同的;二者破裂过程中的波形都具有多重分形特征,破裂时的多重分形谱宽Δf(α)小于破裂前的Δf(α),破裂前的Δf(α)小于破裂后的Δf(α),砂岩试样各阶段的Δf(α)都小于石膏试样对应各阶段的Δf(α)。表明两种试样在破裂时的能量大于破裂前,破裂前的能量大于破裂后,而且石膏在各个阶段的能量小于砂岩对应各阶段的能量。通过对比分析,更加深入了解石膏冲击破裂的规律。石膏和砂岩一样会发生冲击破裂,只是冲击破裂形式不同,而且在同等条件下,石膏破裂产生的能量小于砂岩,为石膏矿冲击地压的防治打下了理论基础。

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 sandstone 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 specimens 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 energy 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.