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开展致密砂岩三轴压缩试验及CT扫描试验,获得不同围压作用下岩石破坏裂纹的几何形态CT图像;利用图像处理、统计学等方法构建破坏裂纹形态的三维空间模型,分析不同围压对破坏裂纹几何形态和分布特征的影响规律,基于能量理论揭示不同三轴应力下岩石破坏时裂纹扩展的能量机制。研究表明:围压对岩石破坏裂纹的形态、数量和空间分布特征有很大的影响。当围压较低时,破坏裂纹数量众多、形态复杂,最终形成主裂纹和次生裂纹交叉分布的裂纹网络结构;围压较高时,最终形成的破坏主裂纹数量减少,次生裂纹消失,形态复杂的裂纹网络被近似直线的破坏裂纹所取代;围压对岩石破坏裂纹扩展的能量耗散和能量释放特征有显著的影响。随着围压的增加,单位体积内的可释放弹性应变能线性增加,而耗散能则呈线性递减趋势。低围压时破坏裂纹的耗散能较大,从而产生几何形态复杂、数量众多的微裂纹。而高围压时的耗散能较少,产生的破坏裂纹数量减少,几何形态趋于简单化、规则化。
The tight sandstone triaxial compression tests and CT scanning tests were carried out to obtain the CT images of the rock under different confining pressures. The three-dimensional space model of the crack damage was constructed by means of image processing and statistics, and the effects of different confining pressures on the failure Crack geometry and distribution characteristics of the impact of law, based on the energy theory reveals different triaxial stress crack failure energy mechanism of crack growth. The research shows that confining pressure has a great influence on the shape, quantity and spatial distribution of rock failure cracks. When the confining pressure is low, the number of failure cracks is large and the shape is complicated. Finally, a cracked network structure is formed in which the main crack and the secondary crack cross each other. When the confining pressure is high, the number of the final cracked main cracks decreases and the secondary cracks disappear, The complex shape of the crack network is replaced by a nearly straight line of failure cracks; the confining pressure has a significant effect on the energy dissipation and energy release characteristics of rock failure crack propagation. With the increase of confining pressure, the elastic strain energy per unit volume increases linearly while the dissipative energy decreases linearly. At low confining pressure, the energy dissipation of crack damage can be larger, resulting in complex geometry and a large number of micro-cracks. While the high confining pressure dissipates energy less, the number of damage cracks generated decreases, the geometry tends to be simplified and regularized.