交叉裂隙砂岩样单轴力学特性与扩展破坏

天然岩体中存在大量交叉裂隙,严重影响岩体构筑物的变形、破坏和失稳规律。本文以类砂岩材料制作主、次不同裂隙倾角岩样为研究对象,通过采用单轴压缩和DIC摄像等试验方法,研究交叉裂隙产状对岩样的力学特性和破坏模式的影响,结果表明：(1)与单一裂隙相比,单裂隙岩样的峰值强度和弹性模量总体上大于含交叉裂隙,表明交叉次裂隙会进一步削弱岩样力学性质。(2)当α≤45°和α＝60°且β≤45°,次裂隙尖端裂纹萌生基本上早于主裂隙,次裂隙尖端裂纹未发生扩展贯通,主裂隙尖端裂纹发生贯通;在α＝60°且β≥60°和α＝90°时,主裂隙尖端裂纹萌生基本上早于次裂隙,次裂隙尖端裂纹扩展贯通,主裂隙尖端裂纹未发生贯通;裂纹主要沿上下方向扩展,水平向裂纹较少。(3)岩样以张拉破坏为主,α＝0°和90°时,岩样全部表现为张拉破坏,α＝30°、45°和60°时,岩样随β增大表现为从剪切破坏—拉剪复合破坏—张拉破坏的变化,主破坏裂纹受主、次裂隙水平向投影较长的一条控制。

Cross Fractured Sandstone Samples Uniaxial Mchanical Properties and Fracture Extended failure study

There are a lot of cross fissures in natural rock mass, which seriously affect the deformation, failure and instability law of rock mass structures. In this paper, sandstone material is made of rock samples with different main and secondary crack dip angles as the research object. By using uniaxial compression and DIC imaging test methods, the influence of cross crack occurrence on the mechanical properties and failure mode of rock samples is studied. The results show that: (1) Compared with the single crack, the peak strength and elastic modulus of the rock sample with single crack are generally greater than those of the rock sample with cross cracks, indicating that cross cracks will further weaken the mechanical properties of the rock sample. (2) When α≤45°, α = 60° and β≤45°, the initiation of the secondary crack tip crack is basically earlier than that of the primary crack, the secondary crack tip crack does not propagate through, and the primary crack tip crack is connected. When α = 60°, β≥60° and α = 90°, the crack initiation at the tip of the primary crack is basically earlier than that at the secondary crack, and the secondary crack extends through, while the primary crack does not. The cracks mainly spread along the direction of up and down, and the horizontal cracks are less. When α = 0° and 90°, all rock samples exhibit tensile failure. When α = 30°, 45° and 60°, rock samples exhibit a change from shear failure to tension-shear composite failure to tension-tensile failure with the increase of β. The main failure crack is controlled by a longer horizontal projection of the main crack and the secondary crack.