干湿循环作用下受荷砂岩损伤劣化特性研究

为研究干湿循环作用下砂岩力学特性的劣化规律,对经历不同干湿循环次数下的弱胶结砂岩进行核磁共振(NMR)及单轴压缩试验,采用声发射技术(AE)实时监测砂岩受荷破坏过程,并采用砂岩孔隙度定义损伤变量,建立干湿循环受荷条件下岩石损伤劣化模型,探究岩体在干湿-受荷作用下的损伤劣化机制。结果表明:①砂岩在循环初期的驰豫时间T₂谱面积增幅最大,且随循环次数的增长不断减小;单轴压缩后的岩样,其T₂谱面积相较于破坏前增长幅度显著。②随循环次数的增加,砂岩试样的塑性变形不断增大,声发射累计振铃数呈降低趋势,降低幅度最大达76.21%。③单轴抗压强度和弹性模量均随干湿循环次数的增大呈指数衰减;引入劣化度表征岩石力学参数的劣化程度,发现岩石单轴抗压强度的劣化速率随孔隙度的增长不断减缓。

Damage and Degradation Characteristics of Loaded Sandstone under Drying-Wetting Cycles

In the purpose of obtaining the deterioration of mechanical properties of sandstone under drying-wetting cycles, we conducted NMR and uniaxial compression tests on weakly cemented sandstones under different drying-wetting cycles, and monitored the damage process of sandstone under loading by using acoustic emission (AE) technology. By defining the porosity of sandstone as damage variable, we built damage deterioration model of rock under cyclic drying-wetting loading to explore the damage deterioration mechanism of loaded rock mass under drying-wetting. Our findings demonstrated that the increment of spectrum area of sandstone peaked at the beginning of cycle, and then attenuated with the proceeding of dry-wet cycles; the T2 spectral area of rock sample after uniaxial compression surged compared with that before failure. With the increase of cycle number, the plastic deformation of sandstone samples augmented, and the cumulative AE ring count reduced by 76.21% to the most. The uniaxial compressive strength and elastic modulus both decayed exponentially with the increase of drying-wetting cycles. By characterizing the deterioration of rock mechanical parameter with the deterioration degree, we found that the deterioration rate of uniaxial compressive strength decreased continuously with the increase of porosity.