酸性环境下含膏盐岩地层中石灰岩孔隙演化及力学特性关联性

Correlation between pore evolution and mechanical properties of limestone in gypsum-salt strata in acidic environment

以济南-莱芜高铁锦屏山隧道内石灰岩为研究对象,开展了含SO_(4)^(2-)酸性环境下石灰岩的核磁共振试验、单轴压缩及巴西劈裂试验,分析了不同pH值的溶液对石灰岩孔隙率、孔径分布、强度参数等的影响规律,揭示了微观孔隙结构损伤与宏观力学参数劣化之间的量化关系。结果表明:1)酸性环境主要作用的孔径尺寸范围为1 nm~1μm,当溶液pH值从7降到3时,试样孔隙率增长率逐渐增大,其孔径分布逐渐由1 nm~1μm占主要比例演化为1 nm~10μm占主要比例;2)随着pH值降低,试样峰值抗压、抗拉强度、弹性模量呈指数降低趋势,峰值应变呈指数增大趋势,单轴试样破坏形式则由劈裂拉伸破坏转变为单斜面剪切破坏;3)随着孔隙损伤变量逐渐增大,试样单轴抗压强度、抗拉强度、弹性模量逐渐减小,单轴压缩应变、劈裂应变逐渐增大。

Acidic groundwater in gypsum-salt strata has a significant dissolution effect on limestone and seriously threatens the construction safety.Limestone in the Jinpingshan Tunnel of Jinan-Laiwu High-Speed Railway is taken as the research object,and the nuclear magnetic resonance test,uniaxial compression test and Brazilian splitting test in acidic environment containing SO_(4)^(2-) are carried out.The changes of porosity,pore size distribution and strength parameters of limestone in solutions with different pH values are analyzed,and the quantitative relationship between the damage of microscopic pore structure and the degradation of macroscopic mechanical parameters is revealed.The results show that:1)the main pore size range of acid environment is 1 nm~1μm.When the solution pH value drops from 7 to 3,the growth rate of porosity of the sample increases gradually,and the main pore size distribution gradually changes from 1 nm~1μm to 1 nm~10μm.2)With the decrease of pH value,the peak compressive strength,tensile strength and elastic modulus of the sample decrease exponentially,and the peak strain increases exponentially.The failure mode of uniaxial specimen changes from splitting tensile failure to single slope shear failure.3)With the gradual increase of the pore damage variable,the uniaxial compressive strength,tensile strength and elastic modulus of the sample decrease gradually,and the uniaxial compressive strain and splitting strain increase gradually.