The Research on Strength and Deformation Behaviors of Buffer/Backfill Material under High-Temperature and High-Pressure Conditions

By using the high-temperature and high-pressure triaxial apparatus, 81 undrained triaxial shearing tests of GMZ bentonite were carried out, and the effects of temperature, confining pressure, water content, and dry density on the deformation and strength characteristics of GMZ bentonite were systematically analyzed. Five results are presented in this paper: (1) confining pressure and dry density have a great influence on the failure forms of GMZ bentonite; under the nonconfined pressure condition, the failure forms of the specimen are brittle failure, and it is the same with high dry density, but the specimens with low dry density and high confining pressure exhibit plastic failure; (2) the strength of GMZ bentonite decreases with increasing water content; the position of the deviator stress-axial strain curve under low dry density rises with the increase of temperature, whereas the location of the curve under high dry density decreases with the rise of temperature; (3) initial Young’s modulus rises with increasing temperature under low dry density, but it is on the contrary under high dry density; with rising water content, initial Young’s modulus generally decreases; (4) Poisson’s ratio rises with rising temperature. The effect of dry density and water content on Poisson’s ratio is insignificant; and (5) the formulae of cohesion and internal friction angle of GMZ bentonite with the changing dry density, water content, and temperature are proposed, respectively. The research results of this paper provide a scientific basis for analyzing the thermo-hydro-mechanical coupling characteristics of buffer materials.