饱水度对砂岩纵波波速及强度影响的试验研究

EXPERIMENTAL RESEARCH ON INFLUENCE OF SATURATION DEGREE ON SANDSTONE LONGITUDINAL WAVE VELOCITY AND STRENGTH

在岩石饱水度、纵波波速及强度的相关性研究中,较少综合地考虑饱水、风干过程及各向异性对岩样纵波波速、强度的影响,而这些问题的研究对于超声技术在岩石物理力学参数测试中具有重要的意义。基于此,选取三峡库区典型层状砂岩,制备垂直层理和平行层理两种岩样,进行岩样的饱水和风干试验。试验结果表明:(1)岩样的纵波波速与饱水度具有明显非线性、非单调的关系,含水岩样的纵波波速不仅与饱水度的大小有关,而且与饱水、风干过程有关。(2)砂岩各向异性明显,在饱水和风干过程中,垂直层理岩样纵波波速的变化幅度明显大于平行层理岩样,饱水后,砂岩的各向异性特征略有增强。(3)在饱水、风干过程中,岩样的抗压强度和纵波波速存在变化规律不一致的现象,岩石矿物颗粒表面和孔壁的吸附水对岩样的弹性模量和强度影响较大,而岩石孔隙内的饱水程度对纵波波速的影响更为明显。研究成果对含水岩石的强度、波速测试分析具有较好的参考价值,同时,相关试验方法也可以为类似试验提供参考。

In the correlation research of rock saturation degree, longitudinal wave velocity and strength, the influences of saturation process and air-drying process on strength and longitudinal wave velocity are lack of comprehensive consideratiom however, the study of these problems is of great significance for ultrasonic technology in the testing of rock physico-mechanical parameters. Based on these, typical layered sandstones in the Three Gorges reservoir area were selected, vertical-bedding samples and parallel-bedding samples were prepared to conduct saturation and air-drying experiment. The experimental results show that： （1） The relationship between longitudinal wave velocity and saturation degree is obviously nonlinear and nonmonotonic; the longitudinal wave velocity of water-bearing rock is not only related to saturation degree, but also associated with saturation process and air-drying process. （2） The anisotropy of sandstone is obvious; the longitudinal wave velocity change range of vertical-bedding rock is significantly greater than that of the parallel-bedding rock in the process of saturation and air-drying~ and the anisotropic characteristics of the sandstone increase slightly under saturated state. （3） In the process of saturation and air-drying, the changing laws of compressive strength and longitudinal wave velocity areinconsistent. The adsorbed water which is on the surface of mineral particles and pore wall has a great influence on elastic modulus and strength~ however, the influence of pore saturation degree on longitudinal wave velocity is more apparent. These research results have important reference value for the strength and longitudinal wave velocity tests of water-bearing rock; what＇s more, the relevant test methods can provide reference for similar test.