High temperatures are caused by radioactive decay during the operation of the geological disposal of high-level nuclear waste. Therefore, investigation of the swelling characteristics of compacted bentonite and its sand mixtures is of considerable importance in assessing the performance of the artificial engineering barrier system in the repository. Swelling tests were carried out on Gaomiaozi (GMZ01) bentonite and its sand mixtures containing 70% and 30% bentonite at variety of temperatures 25, 60, and 90 ℃. The results show that there is a linear relationship between montmorillonite expansion coefficient and temperature (K-T_c) for osmotic expansion, and the maximum expansion strain increases with increasing temperature. The volume deformation of the mixture with high bentonite content at the same temperature can be expressed by the e_m-σ_v fractal relationship, and the bentonite surface fractal dimension is not affected by temperature when immersed within deionized water; the presence of sand skeleton in the mixture with low bentonite content, e_m will deviate from the e_m-σ_v curve when the overlying stress exceeds the stress threshold of the specimen. Combined with the fractal model, a calculation method is proposed to predict the expansion deformation of bentonite-sand mixtures with different sand ratios at different temperatures.

The consolidation tests of Na-bentonite saturated with NaCl, KCl and CaCl₂ are conducted to study the influences of salt-load coupling effect on consolidation property and saturation permeability of bentonite. The results show that: The volume deformation of compacted bentonite decreases with the increase of consolidation stress, and the load grade jumps have a significant effect on the variable properties of bentonite soaked with high concentration NaCl solution. With the increase of vertical consolidation stress under the action of NaCl and CaCl₂, the compacted bentonite samples changed from elastic state to plastic state, and the compression coefficient first increased and then decreased, while the compression coefficient always decreased under the action of KCl solution. The saturation permeability coefficient of bentonite indirectly calculated by Terzaghi one-dimensional consolidation theory ranges from 4.006 × 10^-13 m/s ~ 1.975 × 10^-11 m/s. With the increase of solution concentration, the content of interlayer bound water of montmorillonite decreases, the free water flow path widens, and the permeability coefficient increases correspondingly. By introducing the modified effective force in salt solution, it is found that the equation y = x^-1 × (Alnx+B) can be used to describe the saturated permeability coefficient of bentonite and the effective stress.