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对砂岩进行水-力耦合三轴试验和声发射实时监测,得到水-力耦合作用下砂岩应力-应变曲线和声发射数据。根据试验条件和结果建立离散元颗粒流的水-力耦合双轴模型,研究砂岩声发射和能量演化规律。通过定义耗散能,用耗散能增量较好地诠释了声发射的发展规律。利用微破裂源可追踪声发射局域源,得到水-力耦合条件下的声发射空间分布和裂纹类型。研究表明:(1)孔隙水压力对颗粒的拖拽力削弱了颗粒间的平均接触力,从而降低了砂岩整体强度。(2)孔隙水压力反映出对弹性应变能有一定程度的反复“贮存和清空”作用,造成声发射能量相对离散和峰后的应力波动。(3)渗透压的存在提升了总输入能的耗散效率,降低了总输入能和弹性应变能,须综合考虑总输入能(弹性应变能)和耗散效率才能确定累计耗散能。(4)裂纹分布表现为可能出现与主剪切带呈一定夹角的伴生裂隙带,且受水-力梯度影响,进水端比出水端更密集。(5)张拉裂纹与剪切裂纹的比值于峰值强度处显著增加,峰后趋于稳定。
The sandstone was subjected to water-force coupling triaxial test and acoustic emission monitoring in real time. The stress-strain curve and acoustic emission data of sandstone under water-power coupling were obtained. Based on the experimental conditions and results, a water-power coupled biaxial model of discrete element flow is established to study the acoustic emission and energy evolution of sandstone. By defining the dissipative energy, the law of the development of acoustic emission is well explained by the increment of dissipative energy. Micro-ruptured sources can be used to trace the local sources of acoustic emission and get the spatial distribution of acoustic emission and the types of cracks under water-power coupling conditions. The results show that: (1) The drag force of pore water pressure on particles weakens the average contact force between particles, thus reducing the overall strength of sandstone. (2) Pore water pressure reflects a certain degree of repeated “storage and emptying” of elastic strain energy, resulting in relatively discrete acoustic emission energies and post-peak stress fluctuations. (3) The existence of osmotic pressure enhances the total input energy dissipation efficiency and reduces the total input energy and elastic strain energy. The total input energy (elastic strain energy) and dissipation efficiency can be combined to determine the cumulative dissipation energy. (4) The distribution of cracks shows that there may be an associated fracture zone which is at an angle with the main shear zone. Due to the gradient of water-force, the water inlet end is more dense than the water outlet end. (5) The ratio of tensile crack to shear crack increased significantly at peak intensity and stabilized at peak.