水岩化学作用对砂岩力学特性影响的试验研究

为研究水岩化学作用对砂岩力学特性的影响，将桃源水电站的红砂岩加工成标准圆柱形试样，对其进行不同化学溶液作用下的腐蚀试验，获得红砂岩化学腐蚀过程中相对质量变化规律，同时测量记录各化学溶液pH值。利用岩石三轴测试系统对各种化学溶液浸泡后的红砂岩进行三轴压缩试验，探讨不同的化学溶液对红砂岩力学特性的腐蚀效应，获得水化学溶液对红砂岩强度和变形特性的影响规律。结果表明，试样质量的变化和化学溶液性质有关，试样相对质量变化存在明显差异。pH=13的化学溶液pH值随时间的增长有小幅度下降，其余化学溶液pH值随时间增长均趋于弱碱性(pH≈7.9)。根据溶液pH值的变化、试样相对质量的变化，分析化学溶液对岩石的腐蚀程度。三轴压缩试验结果表明，不同化学溶液对红砂岩力学性质的影响不同。离子成分及pH值均对红砂岩力学特性产生较大影响，各种化学溶液腐蚀后岩石的峰值强度、残余强度、弹性模量均有不同程度的下降。室内试验的结果可为构建红砂岩化学腐蚀条件下本构模型提供重要的试验资料。

EXPERIMENTAL STUDY OF INFLUENCE OF WATER-ROCK CHEMICAL INTERACTION ON MECHANICAL CHARACTERISTICS OF SANDSTONE

In order to investigate the influence of water-rock chemical interaction on the mechanical characteristics of sandstone，the corrosion tests are firstly carried out on the standard specimens of red sandstone taken from the site of Taoyuan hydropower project. The variations of relative qualities of samples with time are obtained as well as the variations of pH values of chemical solutions. Then，a rock triaxial testing machine is used to conduct triaxial compression tests on the red sandstones specimens soaked in six chemical solutions. The effect of chemical solutions with different pH values and ion components on the mechanical characteristics of red sandstones is studied and the influences of chemical solution on strength and deformation characteristics of red sandstones are investigated. The results indicate that the change in rock mass is related to chemical solution. There are obvious differences between different chemical solutions. As to the pH values of chemical solutions，the pH value of solution with the initial pH value equal to 13 decreases very slightly. But the pH values of other solutions finally tend to reach a regular value about 7.9. The corrosion degree is evaluated by measuring the variation of pH values for all solutions and the variation of mass of soaked specimens. According to the results of triaxial compression tests，the mechanical characteristics of rocks are related to the kinds of the chemical solutions. The pH values and ion components have a great impact on the mechanical characteristics of the red sandstone. The peak strength，residual strength and elastic modulus of the rock after corrosion are likely to decrease to a certain degree for different solutions. The failure modes of the samples under different chemical erosions with the same confining pressure have no significant discrepancy. Results obtained from laboratory tests could provide experimental data for the constitutive modelling of sandstone under chemical corrosion.