Experimental study on mechanical properties of weakly weathered gneiss in high temperature water-rich tunnel

To investigate the impact of high-temperature water on gneiss characteristics, the uniaxial compression and Brazilian splitting tests under various high-temperature water bath conditions were performed. Subsequently, the evolution mechanisms of mechanical properties and macroscopic failure characteristics of gneiss were analyzed. Meanwhile, the acoustic emission(AE) monitoring technology, X-ray diffraction(XRD) and scanning electron microscopy(SEM) were utilized to explore the microscopic mechanism of rock failure. The experimental findings reveal that high-temperature water baths significantly diminish the mechanical properties of gneiss, with a more pronounced effect observed with increased water bath time and temperature. Additionally, the failure mode of rocks is also impacted. As the water bath time increases, the failure mode of gneiss transitions from single oblique shear failure to compressive conical shear failure and eventually to shear failure accompanied by tensile cracks, under the conditions of no water bath at room temperature, water bath at 60 ℃ and 92.6 ℃. Moreover, high-temperature water accelerates the weakening effect of the mechanical properties of gneiss compared with room temperature water immersion. This research provides essential theoretical support and engineering guidance for tunnel construction and disaster prevention in high-temperature water environments.