Estimates of strength and cracking behaviors of pre-flawed granite specimens treated by chemical corrosion under triaxial compression tests

Abstract

Four types of granite specimens were prepared and treated by chemical corrosion for 5 and 30 days, which were then used to carry out triaxial compression tests under different confining pressures σ₃. Type A is the intact sample with no preexisting flaws. Types B and C are the samples containing two relatively low-dip flaws and two relatively high-dip flaws, respectively. Type D is the sample including both relatively low-dip and relatively high-dip flaws. The influences of pH value of chemical solutions, flaw distribution, corrosion time and σ₃ on triaxial stress-strain curves and ultimate failure modes are analyzed and discussed. The results show that the pH value of the chemical solution, corrosion time and the arrangement of preexisting flaws play crucial roles in the cracking behaviors of granite specimens. Type A specimens have the largest peak axial deviatoric stress, followed by Type C, Type D, and Type B specimens, respectively. It is because the decrease in the inclination of preexisting flaws induces the weakening effect due to the decrease in the shadow area along the compaction direction. Under a σ₃ of 5 MPa, the peak axial deviatoric stress drops by approximately 40.89%, 29.08%, 4.08%, and 23.53% for pH = 2, 4, 7, and 12, respectively. For intact granite (Type A) specimens, the ultimate failure mode displays a typical shear mode. The connection of two secondary cracks initiated at the tips of preexisting cracks is always the ultimate failure and crack coalescence mode for Type B specimens. The ultimate failure and crack coalescence mode of Types C and D specimens are significantly affected by pH value of the chemical solution, corrosion time and σ₃, which is different from those of Types A and B specimens due to the differences in flow distributions.

Keywords

granites / preexisting flaws / chemical corrosion / triaxial compression / strength / cracking behavior

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Acknowledgments

This study has been partially funded by the National Key Research and Development Program of China, China (Grant No. 2020YFA0711800), the National Natural Science Foundation of China (Grant Nos. 51734009, 51979272, and 52179118), and Natural Science Foundation of Jiangsu Province, China (No. BK20211584). These supports are gratefully acknowledged.

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