富水区的隧道围岩长期受到水化学腐蚀和循环浸水冲刷的影响。为了研究水化学腐蚀和循环浸水冲刷对岩体的损伤机制,模拟不同pH值(7、5、3)和流速(0、300、900 mm·s-1)的水化学环境,开展为期60 d的流纹岩循环浸水试验,并通过三轴压缩试验以及电镜扫描、数字图像相关技术、XRD衍射试验,分析了岩石力学参数的劣化和损伤机制。结果表明:(1)水化学溶液的pH值越低、流速越大,流纹岩微观结构、孔隙率、弹性纵波、内摩擦角与黏聚力负效应越大;(2)三轴压缩试验中,pH=7环境下流纹岩试样的破坏模式主要为剪切滑移破坏,pH=5、3环境下为柱状劈裂破坏;(3)试样的全局应变场和局部化带出现位置与破坏位置一致,且溶液流速越大,试样的应变值越大;(4)循环浸水试验初期,试样质量损失因子及弹性纵波劣化速率较快,但随着试验时间延长,劣化速率逐渐趋于稳定;(5)在恒定流速下,流纹岩的峰值强度和体积应变最大值随围压增加呈递增趋势,而在恒定围压下,则随流速增大而减小。
The tunnel surrounding rock in water-rich regions is subjected to long-term chemical corrosion and cyclical water immersion erosion. In order to investigate the damage mechanisms of chemical corrosion and cyclical water immersion on rock masses, a 60-day cyclical water immersion test was conducted on sandstone specimens under simulated water chemistry environments with different pH values (7, 5, 3) and flow velocities (0, 300, 900 mm·s-1). The degradation and damage mechanisms of rock mechanical parameters were analyzed through triaxial compression tests and techniques such as scanning electron microscopy, digital image correlation, and XRD diffraction experiments. The results reveal that: (1) Lower pH values and higher flow velocities in the chemical solution are associated with greater microstructural damage, porosity increase, attenuation of elastic wave velocity, internal friction angle reduction, and cohesive strength decline in the sandstone specimens. (2) In the triaxial compression tests, the failure mode of the sandstone specimens under pH=7 environment is mainly shear slip failure, while under pH=5 and 3 environments, columnar splitting failure is prominent. The globally distributed strain fields and localized deformation bands coincided with the location of failure, with higher flow velocities corresponding to larger strain values in the specimens. (3) During the initial stage of water immersion testing, the mass loss factor and degradation rate of elastic wave velocity decreased gradually over time. (4) Under constant flow velocity, the peak strength and maximum volumetric strain of sandstone increased with increasing confining pressure, while under constant confining pressure, they decreased with higher flow velocities.
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