Correlation between pore evolution and mechanical properties of limestone in gypsum-salt strata in acidic environment
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 SO42- 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～1 μm.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～1 μm to 1 nm～10 μm.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.
gypsum-salt strataacid dissolutionnuclear magnetic resonancepore structuremechanical property
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NSTL
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