冻融作用对条带状磁铁石英岩物理力学性能影响试验研究

Experimental Research on the Physical and Mechanical Properties of Striped MagnetiteQuartzite under Freeze-thaw Effect

为研究冻融作用对条带状磁铁石英岩物理力学特性的影响,对条带状磁铁石英岩进行了矿物成分与结构分析,在对该岩石进行了最高280次的冻融循环试验后,展开了基于应变监测的单轴压缩试验。试验结果表明:条带状磁铁石英岩主要成分为石英和磁铁矿物,其结构致密,原生裂隙主要为贯穿条带分布;随冻融循环周期增加,岩样饱水质量、开口孔隙率和纵波波速呈阶段式变化;自干燥至冻融280次,岩样的单轴抗压强度、弹性模量分别下降了46.93%、61.98%,在冻融前、中期岩样单轴抗压强度、弹性模量下降最为显著;根据岩石变形特征获得不同冻融循环周期下岩样的应力特征值,岩样压密应力、起裂应力随冻融循环周期的变化幅度最为显著,并结合其与峰值应力的占比变化情况,发现岩样在低、中荷载下其内部裂隙活跃程度与冻融循环周期存在较高的相关性。

For the purpose of researching the influence of freeze-thaw on the physical and mechanical properties of striped magnetite quartzite,mineral composition and structure analysis were conducted on the striped magnetite quartzite,and uniaxial compression tests based on strain monitoring were carried out after freeze-thaw cycles of up to 280 cycles.The test results showed that the striped magnetite quartzite is mainly composed of quartz and magnetite minerals,and its structure is dense,and the primary fractures are mainly distributed through the strip.The rock sample saturation mass,open porosity and longitudinal wave velocity showed phase changes with increasing freeze-thaw cycles;The uniaxial compressive strength and elastic modulus of rock samples decreased from dryness to the 280th freeze-thaw cycle by 46.93%and 61.98%,the most significant decrease in uniaxial compressive strength and elastic modulus of rock samples before and in the middle of the freeze-thaw cycles;The stress characteristics of the rock samples under different freeze-thaw cycles were obtained based on the deformation characteristics of the rocks,and the most significant changes in the compressive stress and cracking stress with the freeze-thaw cycles of the rock samples,and combined with the changes in the percentage of their peak stress,it was found that there was a high correlation between the internal fracture activity and the freeze-thaw cycles of the rock samples under low and medium loadings.