含共面裂隙群砂岩强度与破裂特征的试验研究

节理岩体力学行为是地下工程稳定分析及支护设计的基础。采用岩石力学伺服试验机对含充填共面裂隙群砂岩试样进行单轴加载试验,分析了连通率和充填方式对砂岩强度及变形破裂特征的影响规律。试验结果表明:裂隙砂岩的力学性能较完整砂岩呈现出显著的劣化,且随着裂隙连通率的增大,峰值强度、峰值应变及弹性模量均逐渐减小;试样破裂过程中预制裂隙尖端先后出现Ⅰ类张拉裂纹和Ⅱ类剪切裂纹,但最终的失稳破裂面由II类裂纹扩展形成,Ⅰ类裂纹和Ⅱ类裂纹与预制裂隙的夹角随着裂隙连通率的增大逐渐增大;受充填方式的影响,裂隙砂岩的强度及变形特征均呈现出显著增大的趋势,而弹性模量提升幅度相对较小。

STRENGTH AND FRACTURE CHARACTERISTICS OF SANDSTONE CONTAINING COPLANAR FISSURE GROUP

The mechanical behavior of joint rock is an important factor in underground engineering stability analysis and support design. By employing rock mechanics servo testing system, a series of uniaxial loading tests were conducted on sandstone samples containing coplanar fissures to investigate the strength and failure characteristics of sandstone with different connection rate and filling pattern. The results show that the mechanical parameters of sandstone containing fissures are remarkably lower than that of intact sandstone. Peak strength, peak strain and elasticity modulus of sandstone samples all decrease gradually with the increase of connection rate. Tension crack I and shear crack II appear successively at the end of preset fissures during sandstone samples failure, and the ultimate failure surface of sandstone samples is formed by crack Ⅱ. The angle between preset fissures and extending cracks (Ⅰ and Ⅱ) increases gradually with the increase of connection rate. Also, the filling pattern has a significant influence on the strength and deformation behavior of sandstone samples, and relatively smaller effect on the modulus elasticity.