Abstract Currently, the construction of railroads in western China is accelerating. In high geothermal areas, the tunnel is subjected to multi-field coupling effects such as complex rock properties, high temperature, high geo-stress, and excavation unloading. Tunnel excavation causes disturbances to the bedded rock and even the weaker layers to open or slip, resulting in the deterioration of the macroscopic mechanical properties of the rock mass. Under high temperature, the strength of rock is reduced, triggering brittle fractures (rock blast) and other engineering disasters. Thus, based on the collection of gneiss samples from high-temperature tunnels, this study carried out Hopkins lever impact experiments to elucidate the temperature effect and the influence of different foliations angles on the anisotropic mechanical properties of gneiss. The results showed that: (1) At higher temperatures, the rock exhibited a greater elastic deformation capacity. For gneiss, the mechanical strength was lowest at a foliations angle of 45°, approximately 50 MPa, whereas it reached the overall peak strength at a foliations angle of 90°, approximately 200 MPa. (2) The damage mode of gneiss was strongly influenced by the foliations angle. Macroscopically, damage predominantly occurred along the gneiss foliation surfaces, and penetration damage became more pronounced when the foliations angle approached 45°. Microscopically, the resistance to fracture increased with rising temperature; (3) A damage constitutive model considering the temperature—foliations angle—axial pressure destruction was established. It could better match the experimental stress–strain results. The research results provided a theoretical basis for the study of the damage mechanism of gneiss under dynamic and static loads and temperature.
Huang et al. (Wed,) studied this question.