深部裂隙岩体中弹性波传播与衰减规律试验研究

为研究深埋裂隙岩体中弹性波的传播与衰减规律,采用室内模型试验,得到弹性波在深部裂隙岩体中传播时的波速值及首波波幅值随地应力变化的曲线,并对试验过程中弹性波的传播与衰减规律进行分析,对裂隙岩体中弹性波的波速增量、衰减程度与围压、裂隙数量、裂隙分布角度之间的关系进行了探讨和拟合。试验研究结果表明:在三轴压缩试验中,当围压一定而轴向压力增加时,弹性波波速值的变化经历快速增长、缓慢增长、基本稳定、快速降低4个阶段,并在轴向应力达到峰值强度的60%时,波速值迅速下降,因此可判断该点为岩体中裂纹开始扩展的起始点,同样首波波幅值的衰减程度也呈现出类似变化规律;在三轴拉压试验中,当围压一定而轴向拉力增加的过程中,弹性波波速值不断降低,波幅值的衰减程度也是不断增强。围压、裂隙角度、裂隙数量对弹性波的传播速度和衰减程度均产生一定影响,影响程度的敏感性为:裂隙数量围压裂隙角度。

EXPERIMENTAL STUDY OF PROPAGATION AND ATTENUATION OF ELASTIC WAVE IN DEEP ROCK MASS WITH JOINTS

Laboratory modeling tests were performed to study the elastic wave propagation and attenuation in deep-buried rock mass with joints and the velocity and amplitude variation of elastic wave in jointed rock mass under different in-situ stresses were obtained. The propagation and attenuation of elastic wave in jointed rock mass were analyzed to study the relationships of the velocity increment and attenuation of elastic waves，the confining pressure，the number and angles of joints. The results of a triaxial compression test with constant confining pressure and increasing axial compression pressure showed that the change of elastic wave velocity had four phases：rapid growth，slow growth，stable state and rapid reduction. When the axial stress reached 60% of its strength，the velocity reduced rapidly，which indicated that the rock started to expand. The attenuation of the first wave amplitudes showed the similar trend of variation. In a triaxial tension-compression test with constant confining pressure and increasing axial tension pressure，the elastic wave velocity reduced gradually while the attenuation of amplitude grew. The results showed that the confining pressure，the angles and number of joints were all influential to the velocity and the attenuation of elastic wave. The degrees of influence sensitivity were in the decreasing order as：the number of joints＞confining pressure＞angles of joints.