单轴压缩下酸腐蚀花岗岩能量演化与分形特征

Energy evolution and fractal characteristics of acid corroded granite underuniaxial compression

利用单轴压缩、声发射监测及X射线衍射试验手段分析了不同腐蚀时间花岗岩力学特性,获得了声发射特征参数变化规律,从腐蚀机制角度分析了花岗岩内部结构劣化原因,并对岩样破坏过程中能量演化规律及破碎分形特征进行研究。主要结论如下:随着腐蚀时间增加,单轴抗压强度和弹性模量分别降低了25.6%和38.3%;声发射累计振铃计数降低,高水平声发射振铃计数持续时间缩短;岩样内部结构因矿物成分分解而劣化,而二氧化硅悬浮物又会延缓这一劣化,导致力学参数折减速率与腐蚀时间呈负相关;塑性阶段之前,腐蚀岩样耗散能增长率较大,其内部损伤已经快速发育,耗散能也处于较高水平,在塑性阶段,损伤发育程度低于未腐蚀岩样;耗散能随腐蚀时间增加而降低,但耗散能占比由29.1%升高到35.0%,延性提高;总能量和弹性应变能的峰值、增长速率均随着腐蚀时间增加而减小,内部结构劣化程度增大,岩样吸能能力和储能极限降低;破坏模式由剪切-劈裂破坏转变为剪切破坏,中、小粒径碎块质量占比由44.6%降低到22.8%,破碎分形维数降低了9.5%,破碎程度降低,用于破碎的耗散能也随之降低。

By means of uniaxial compression test,acoustic emission(AE)monitoring approach and X-ray diffraction technique,we analyzed the mechanical properties of granite at different corrosion times and obtained the variation law of AE characteristic parameters.The causes of internal structure deterioration of granite were analyzed from the perspective of corrosion mechanism,and the energy evolution law and fractal characteristics of fragmentation during the destruction of rock samples were investigated.The test results showed that with the increase of corrosion time,the uniaxial compressive strength and elastic modulus decrease by 25.6%and 38.3%,respectively.The cumulative AE ring count is reduced,and the duration of high-level AE ring count is shortened.The internal structure of the rock sample deteriorates due to the decomposition of mineral components,and the silica suspension delays this deterioration,resulting in a negative correlation between the reduction rate of mechanical parameters and the corrosion time.Before the plastic stage,the growth rate of dissipated energy of corroded rock sample is large,its internal damage has developed rapidly,and the dissipated energy is also at a high level.At the plastic stage,the degree of damage development is lower than that of non-corroded rock sample.The dissipated energy decreases with the increase of corrosion time,but the proportion of dissipated energy increases from 29.1%to 35.0%,and the ductility increases.The peak value and growth rate of total energy and elastic strain energy decrease with the increase of corrosion time,the deterioration degree of internal structure increases,and the energy absorption capacity and energy storage limit of rock samples decrease.The failure mode changes from shear splitting failure to shear failure.The mass proportion of medium and small particle size fragments is reduced from 44.6%to 22.8%,the fractal dimension of fragmentation is reduced by 9.5%,the degree of fragmentation is reduced,and the dissipated energy for fragmentation is also reduced.