Experimental study on the effect of thermal-chemical coupling on tension-shear fracture characteristics of cracked Karst limestone

Abstract

In the natural environment, the main control structural plane of dangerous rock in karst area is subjected to complex coupling effects of temperature, acid rain and tension-shear force. However, the multi-field coupling effect on the stability of dangerous rocks is still unclear. To further probe this issue, first, the chemical solution immersion tests were carried out at pH of 2, 3, 4, 5 and temperature of 20, 30, 40, 60℃ for pre-cracked limestone, and room temperature rock samples at pH of 7 were used as comparison samples. Second, the tension-shear test on the soaked rock samples were conducted using the self-developed tension-shear test device. The crack propagation and failure modes of tension-shear pre-cracked limestone with different temperatures and pH value solutions were analyzed. Finally, the mineral composition, microstructure and damage degree of different rock samples were tested and analyzed by X-ray diffraction test, SEM test and inductively coupled ion emission spectrometer. The test results show that the temperature and acidity are negatively correlated with the tension-shear strength of limestone. The higher the temperature or acidity, the smaller the ultimate tension-shear peak load. The main mineral composition of limestone is calcite, and the pore size on the rock surface reflects the variation trend of cracking under tension-shear loading. The rock mass loss rate is positively correlated with the temperature and negatively correlated with the pH value, both of which can affect the progress of water rock chemistry and have a certain impact on the degree of rock deterioration.