单轴压缩下三裂隙黄砂岩力学特性及裂纹扩展试验研究

Experimental Study on Mechanical Properties and Crack Propagation of Three-fissure Yellow Sandstone under Uniaxial Compression

为了研究单轴压缩下含裂隙黄砂岩的损伤劣化机理,利用伺服压力机对预制断续三裂隙黄砂岩进行单轴压缩试验,并结合高清摄像机录像对试样破坏全过程进行监控,进而分析了不同中心裂隙倾角α对三裂隙黄砂岩力学特性、裂纹扩展规律及破坏模式的影响。结果表明,随着中心裂隙倾角α的增加:(1)三裂隙黄砂岩单轴抗压强度先增大后减小,与完整砂岩试样相比,三裂隙黄砂岩试样峰值强度降低明显;(2)初始裂纹由岩桥区域附近萌生,α=15°、30°时垂直于中心裂隙B,α=45°时发展为连通裂隙AB、BC尖端并与中心裂隙B成一定角度,次生裂纹沿轴向扩展,主裂纹沿试样上下端面及边缘扩展;(3)裂隙砂岩试样的破坏模式由张拉破坏变为劈裂破坏,最后变为剪切破坏。

In order to study the damage and deterioration mechanism of fractured yellow sandstone under uniaxial compression,a servo press was used to perform uniaxial compression test on prefabricated intermittent three-fissure yellow sandstone.Combined with high-definition camera video to monitor the whole process of sample destruction,the influence of different central fissure dip angleαon the mechanical properties,crack propagation law and failure mode of three-fissure yellow sandstone is analyzed.The results show that,with the increase of the central fissure dip angleα:(1)the uniaxial compressive strength of the three-fissure yellow sandstone increases first and then decreases.Compared with the intact sandstone sample,the peak strength of the three-fissure yellow sandstone sample decreases significantly;(2)The initial crack originated from the vicinity of the rock bridge area.Whenα=15°and 30°,it is perpendicular to the central crack B.Whenα=45°,it develops into the tip of the connected cracks AB and BC and forms a certain angle with the central crack B.The secondary cracks propagate in the axial direction,and the main cracks propagate along the upper and lower end surfaces and edges of the specimen;(3)The failure mode of the fractured sandstone specimen changes from tensile failure to split failure,and finally to shear failure.