Investigation of the shearing behavior and mechanism of serrated granite-concrete interface considering the temperature difference initial damage

The shearing mechanism of the Granite-Concrete Interface (GCI) is crucial for the safety evaluation of deep-buried tunnels in plateau areas. The combined effects of high-temperature rock mass and low-temperature environments can cause Temperature Difference (TD) damage to the surrounding rock. However, GCI's shear mechanical behavior and mechanisms under various TDs require further investigation. This study conducts direct shear tests of GCI damaged by different TDs ((90°C, −30°C), (100°C, −20°C), (110°C, −10°C), and (120°C, 0°C)). It analyzes the impact of TD damage on the shear strength, three-dimensional morphology of shear fractures, and acoustic emission (AE) characteristics of GCI. The results indicated that as temperature increases, the shear strength of GCI improves, and the concrete volume loss in shear fractures diminishes. Under various TD paths, the cumulative energy curve of AE exhibits an 'S' shape. TD has a minimal impact on the precursor (b-value decrease) of GCI failure. The shear damage constitutive model created using a piecewise function struggles to represent the influence of TD damage. In contrast, the stress-strain prediction model based on data-driven approaches demonstrates broad applicability. Thermal expansion caused by high temperatures facilitates increased friction between mineral particles, enhancing the shearing strength of GCI (for 120°C, 0°C). In addition, high temperatures lead to the evaporation of free water and affect the freezing of GCI at low temperatures. When the temperature falls below −20°C, frost heave damage contributes to the deterioration of GCI shear strength.