基于小波变换的岩芯卸荷扰动声学反应分析

 现行国家规范将岩体与岩块的纵波速度比的平方定义为岩体的完整性，这是由于通常情况下原位岩体的纵波波速低于其中岩块的波速，岩体越破碎，波速低得越多。通过对南京地铁工程围岩声波测井及岩芯声波测量发现，用通常手段得到的一部分岩体的测井波速反而大于岩芯波速，分析其原因主要是岩芯受卸荷及钻取扰动影响造成的。为更好地对岩芯卸荷扰动的声学反应进行分析，基于小波变换方法，将岩芯声波信号分解成不同频带通道的小波分量，进而对其进行时频分析，得到的各频带分量及其加权频谱参数与岩芯卸荷扰动敏感程度具有良好的相关性，表明该方法在分析岩芯卸荷扰动问题上具有优越性。

ANALYSIS OF ACOUSTIC RESPONSES TO ROCK CORE UNLOADING DISTURBANCE BASED ON WAVELET TRANSFORMATION

According to the present national standards，the square of the ratio of longitudinal wave(P-wave) velocity of rock mass to that of rock block is defined as intactness index of rock mass. It is well known that the P-wave velocity of in-situ rock mass is believed to be lower than that of relevant rock block commonly. The more broken the rock mass is，the lower its P-wave velocity than that of rock block is. Acoustic logging and wave velocity measurement of rock cores are applied to bedrock of Nanjing subway engineering. It is found that most wave velocities of rock mass are greater than those of rock cores；and the cause is unloading-disturbance influence on rock cores. In order to analyze the acoustic responses of rock core unloading-disturbance more availably，wavelet transformation method is applied to decompose the rock core acoustic signals into wavelet components belonging to various frequency channels；and weight spectrum parameters are given after time-frequency analysis of the channel signals. There are good relationships between the data of rock core acoustic signals and rock core sensitivity degree of unloading-disturbance. It indicates that the wavelet transformation method is superior for rock cores unloading-disturbance analysis.