真三轴压缩岩样破裂过程中 S 波尾波波列振幅和卓越频率的变化(英文)

VARIATIONS OF THE AMPLITUDE AND THE PREDOMINANTFREQUENCY OF THE S-WAVE CODA TRAINS DURING THEFRACTURE-PREPARING PROCESS OF ROCK SAMPLES UNDERTRUE TRIAXIAL COMPRESSIONS

我们利用固体传压真三轴压机,50×50×200mm^3大理岩试件,600KC S波探头,分别观测了在等应力压缩和差应力压缩时S波尾波波列振幅和卓越频率衰减系数K和α的变化特征。结果表明:在等应力(σ_1=σ_2=σ_3)压缩时,随着压力的增加,波列振幅和卓越频率衰减系数K、α逐步增大。在差应力(σ_1>σ_2>σ_3)压缩至断裂时,σ_3和σ_2方向的K、α变化各异。当σ_1低于破裂应力σ_(1p)的20%时,两个方向的K、α都随着压力增加。当σ_1大于20%σ_(1p)而继续增加至50%时,K、α大体都保持平稳值,而当σ_1超过60%σ_(1p)时,σ_2方向的K逐步变大,α逐步减小。而σ_3方向的K、α则逐步减小。当出现前兆应力降后,σ_3方向的K、α都回升,接着主破裂来临。破裂后,σ_2方向的K、α增大,而σ_3方向的K、α则减小。同时,波列图清楚地表明,S波最大振幅的变化对K有着重要的影响。

Using the solid transmission, true triaxial Press, marble specimens, 50×50×200 mm in size, and 600 kc S-wave sensor, the variation features of the attenuation coefficients K and a respectively of the wave-train amplitude of the S-wave coda and their predominant frequencies under equal- and differential-compressions are measured. Results of the study show: Under equal pressures (σ1 =σ2 =σ3), the attenuation coefficients K and a of the amplitude and the predominant frequencies show gradual increases with the increase of the pressure. Under the differnetial pressure (σ1>σ2>σ3), when the pressure increases to the rupturing, coefficients K and a show different variations along the σ3- andσ2-directions. When σ1 is lower than 20% of the rupturing stress σ1p, the K- and α-coefficients along both directions all increase along with the stress rises. When σ1 is higer than 20% of σ1p and continues to rise till it reaches 50% of am, the K-and α-coefficients generally show stable values. When σ1 is greater than 60% of σ1p,>, K along the. σ2-direction gradually increases and α gradually drops whereas K and α along the σ3-directon all gradually decrease. After the emergence of the precursory stress drops, K and α along the σ3-direction all show restored increases which is followed by the outburst of the major rupturing. After the rupturing, K and α along the σ2-direction increase whereas K and α along the σ3-direction decrease. Meanwhile, it can be clearly observed from the wave-train records that variations of the maximum amplitude of the S-waves can exert crucial influences on the K-vavlues.