砒砂岩的三轴强度特性及微观结构研究

Study on Triaxial Strength Characteristics and Microstructure of the Arsenic Sandstone

为深入认识黄土高原地区砒砂岩干燥时坚如磐石、遇水后溃散泥化的微观机理,对不同粒度砒砂岩原状试样进行三轴剪切试验和CT扫描,获取不同粒度砒砂岩的强度特征和微结构特征,并分析了砒砂岩孔径的分布特点。结果表明:砒砂岩试样的抗剪强度随粒度增大而降低,试样的峰值强度与固结围压存在良好的线性关系;由CT扫描得到的砒砂岩二维图像显示不同粒度试样的孔隙形态非常复杂;从三维重构模型的统计结果发现砒砂岩平均孔隙半径随砒砂岩粒径的增大而升高;砒砂岩的强度存在明显的粒度效应,砒砂岩粒度大小决定了内部孔隙的分布情况,进而引起强度的改变。

In order to further understand the microscopic mechanism of arsenic sandstone which is hard as rock in dry state and muddy in wa⁃ter,triaxial shear test and CT scan test were carried out for obtaining the strength characteristics and microstructure characteristics of arsenic sandstones in different grain grades.The results show that the strength of sandstone sample decreases with the increase of grain size in triaxial shear test.There is a good linear relationship between peak strength and consolidation confining pressure.The two⁃dimensional and three⁃di⁃mensional reconstruction images of sandstone samples can be obtained by CT scanning.It is found that the porosity and average pore radius of sandstone increase with the increase of particle size.The strength of sandstone has obvious“particle size effect”.The smaller the particle size of arsenic sandstone,the smaller its porosity,and thus the higher the strength.