板岩遇水软化的微观结构及力学特性研究

通过偏光显微镜、电子扫描电镜、粉晶X射线衍射，测定板岩泡水过程中吸水率、润湿角的变化，不同浸泡时间下的矿物颗粒微观结构、孔隙度的变化，并通过三轴压缩实验，研究了板岩泡水后发生软化的过程与机理。研究表明：板岩在浸泡后吸水率受板岩内层理面的产状、密度等参数的影响而改变，随着泡水时间的增加，吸水率在最初两天内变化较大，后期变化不太明显；板岩内部矿物颗粒在浸泡过程中产生体积膨胀，胶结变得松散，颗粒膨胀的时间稍滞后于吸水率的变化过程；三轴压缩实验结果显示，板岩浸泡后发生软化，峰值抗压强度随着吸水率增加按负对数规律降低；微观结构分析及润湿角的降低趋势表明，随浸泡时间延长，矿物颗粒之间的毛细管力、表面张力降低，使得板岩内部黏结力降低，宏观上则体现为岩石发生软化；在垂直于层理面方向更易发生体积膨胀，因此岩石在浸泡后更易沿着层理面产生破坏。

Study on variation of microstructure and mechanical properties of water-weakening slates

The objective was to analyze the water-weakening feature and the weakening mechanism of the slate taken from the engineering of the west route of water transfer from south to north in China.Some experiments were done including measuring the change of water absorptions,contact angles,the microstructures of the minerals,the porosities and the strength of the rocks in different absorption by SEM,powder X-ray diffraction analysis and the triaxial compression experiment.Some conclusions are drawn from these experiments as follows:(1) when flooding into water,the absorption was affected by the location and density of the layer surfaces,and increased with the dipping time in the first few days till it kept stable at last;(2) in the SEM images the grains of the slates bulged and the structure relaxed,which made the porosity increased without confinement and the volume bulge lagged behind the water absorption;(3) the triaxial compression results show that the slates weakened and the peak strength of the slates declined with the absorption increased in minus logarithm law;(4) from the variety trends of microstructure and contact,the capillary force and the tension force of the slates decreased with the absorption,which made the adhesive force declined.In the macroscopic view,it is shown that the slates weakened with water.The slate is anisotropic which made the volume dilation in the perpendicular direction to the layers bigger than the parallel direction.As a result,the slate are easier to failure following the layer surfaces.