Abstract: During the preparing process from compression to fracture,the elastic waves of gneiss have obvious various characteristics along the σ3 direction( obliquely crossing with main fracture plane): the various state of the first arrival time of P,S wave shows a shape of relatively high value～stability～high value～decrement,and the ratio of trave time has shape of stabiltity～low value～increment. The amplitude of P,S waves shows a shape of low value～stability high value decrement(low value) and their ratios have a shape of relatively stabllty～very high value～decrement. The variation state of attenuation coefficient of the wave trian shows a shape of stability～low value～increment.The main reason for those variations is the openingand closing of micro-cracks,the nonsynchronous variation of P, S wave and the difference of their variations.

Key words: Triaxial compression test, Rupture process, Elastic wave, Gneisse

摘要： 片麻岩在真三轴压缩至主破裂的孕育过程中,沿σ₃方向(与主破裂面斜交)的弹性波有显着的特征变化；P波、S波的初至波走时变化呈现略高～平稳～高值～(回降)的形式,走时比呈现平稳～低值～回升的变化特征。振幅呈现低值～平稳高值～下降～(低值)变化形态,振幅比呈现相对稳定～甚高值～回降变化形态。波列振幅衰减系数呈现稳定值～低值～回升变化形态。微裂隙的开闭和P,S波的非同步变化及相对变化量的不同是上述特征变化的主要原因。

关键词: 三轴压缩试验, 破裂过程, 弹性波, 片麻岩