Research Of Strength And Volume Change Of Buffer Material In High Temperatura And Pressure From High-Level Radioactive Waste Repository

Studied on GMZ001 bentonite and its sand mixed materials, selected the improved temperature controled triaxial test apparatus and the high-precision temperature controlled box as the main tools, this thesis presents a comprehensive and thorough research as well as theoretical analysis on the shear strength, volume change and nonlinear parameters of triaxial test by controlling the different dry density, sand factor, water ratio, temperature and confining pressure. The main work and the latest achieved results are as follows.(1)At the aspect of shear strength, as the water ratio increases, the specimen’s shear strength declined sharply, so as the cohesion and the internal friction angle.The shear strength is increased as the compressure increases.The shear strength is increased as the temperature increases in low dry density while the shear strength decreased as the temperature increases in high dry density.(2)At the aspect of volume change, the specimen’s volume change is decreased as the temperature increases, some even show the dilatancy shear failure. The volume change is increased as the axial strain increases in high confining pressure. Pure bentonite specimen’s volume change nearly shows no relevance to the water ratio in low confining pressure, but it is decreased as water ratio increases. Bentonite-sand mixture’s volume change is decreased with water ratio increases, and it is increased with the increase of sand factor in low confining pressure while it’s not obviously in high confining pressure.(3)At the aspect of strength parameter, we can got the fitting formula of cohesion and internal friction angle of pure bentonite and bentonite-sand mixture under different dry density,water ratio, sand factor and temperature respectively by fitting of the cohesion and internal friction angle which we got from the 81 pure bentonite specimen and the 96 sand-bentonite mixture specimen. The specimens’cohesion is increased with the temperature increases under low dry density while it’s on the contrary under high dry density. Temperature show no significant impact on internal friction angle. The cohesion and internal friction angle were all decreased with the increase of water ratio.(4)At the aspect of nonlinear parameters, the Young’s modulus of specimens is almost increased as the temperature increase under the dry density of 1.4 g/cm3 and 1.6 g/cm3 while it’s on the contrary under the dry density of 1.8 g/cm3. As the water ratio increase, the specimens’Young’s modulus were almost decreased, but the sand-bentonite mixture’s Poisson ratio and failure ratio are increased,the pure bentonite’s failure ratio shows no relevant to the water ratio. As the confining pressure increase, the pure bentonite’s failure ratio were also increased, but poisson ratio are decreased. The sand-bentonite mixture’s failure ratio and poisson ratio were decreased as the confining pressure decrease.The result of this research provided the basic data and scientific proof for the buffer material’s design and selecting in high-level radioactive waste repository for our country in the future.