断续节理岩体声学力学特性试验研究

Experimental study on acoustic and mechanical properties of intermittent jointed rock mass

断续节理对岩体强度的影响及其评价方法一直是岩体力学领域研究的热点和难点。采用石膏制作含有不同节理倾角、密度及连通率组合的断续节理岩体试样,共计45组,每组试样先后开展超声波波速测试和单轴压缩试验,分析试样力学参数和声学参数间的关联特性,探索节理分布特征对岩体破坏模式及单轴抗压强度的影响,最终提出断续节理岩体单轴抗压强度的取值方法。结果表明,纵波波速与节理连通率呈正相关,随节理倾角增大近似"V"型先减后增;单轴抗压强度和弹性模量随节理连通率的增大而增大;单轴抗压强度随节理倾角的增大近似"U"型先减后增;总结提出了断续节理岩体的4种破坏模式,并认为节理与加载方向成45°夹角时最易破坏;最终提出了基于岩体及岩石纵波波速、岩石内摩擦角、节理倾角的岩体单轴抗压强度与岩石单轴抗压强度之间的拟合关系。

The influence of intermittent joints on the strength of rock masses and its evaluation method have always been one of the hotspots and difficulties in the field of rock mass mechanics. In this paper,45 samples of intermittent jointed rock mass are made from gypsum with different combinations of joint inclination,density connectivity,and ultrasonic wave speed and uniaxial compression strength(UCS) tests are performed. The correlation characteristics between the mechanical and acoustic parameters are investigated,the influence of the distribution characteristics of joints on the rock mass failure mode and UCS is explored and consequently a determination method of the UCS of intermittent jointed rock mass is proposed. The results show that the P-wave velocity is positively correlated with the joint connectivity and has an approximately V-shaped change with increasing the joint dip angle,and that both the UCS and the elastic modulus(E) of the jointed rock mass increase with increasing the joint connectivity and the UCS presents an approximately U-shaped change with increasing the joint dip angle. Four fracturing modes of intermittent jointed rock masses are proposed and it is pointed out that samples are most prone to fail when the joint forms a 45°angle with the loading direction. Finally,a fitting relationship between the UCS of jointed rock masses and intact rock block is proposed by considering not only the P-wave velocity but also the internal friction angle of the rock block and the joint dip angle.