不同应力路径下砂岩力学特性的试验研究

利用WDT–1500多功能材料试验机对砂岩试样进行定围升轴、卸围升轴及定轴卸围这3种不同应力路径下的三轴试验，并从变形特性、强度特性和破坏特性及其机制分析等方面对砂岩试样的力学特性进行对比分析研究。结果表明：相对于定围升轴，卸围升轴及定轴卸围下砂岩的强度有所降低，而其侧向变形和相同主应力下的扩容量明显增加，尤其在卸围升轴下的扩容量最大；不同应力路径下，砂岩的变形和强度特性主要受初始轴压和初始围压的影响，而围压加载速率对砂岩力学性质的影响不明显。定围升轴下试样呈现剪切破坏，而卸围升轴和定轴卸围时试样常常呈现出张剪破坏特征。

EXPERIMENTAL STUDY OF MECHANICAL CHARACTERISTICS OF SANDSTONE UNDER DIFFERENT LOADING PATHS

Triaxial compression for sandstone sample under three paths，i.e. axial loading and radial constant，axial loading and radial unloading，axial constant and radial unloading are realized on WDT–1500 reactive material testing machine. The mechanical characteristic of sandstone comparatively from deformation property，strength property，failure feature and its mechanism are analyzed and researched. The test results show that strength of sandstone is reduced，but deformation of radial and its expansion of capacity under the same principal stress increase significantly under axial loading and radial unloading，axial constant and radial unloading relative to axial loading and constant radial，and especially under axial loading and radial unloading the expansion of capacity is largest；the deformation property and strength property of sandstone under these three stress paths are mainly influenced by initial axial pressure and initial radial pressure，but the influence of the unloading speed of radial pressure on mechanical characteristics of sandstone is not clear. The failure characteristics of samples under axial loading and constant radial present shear failure，but the failure characteristics of samples often present mixed tensile-shear failure under axial loading and radial unloading，axial constant and radial unloading.