| By simulating the temperature-alkali environment of compacted bentonite in the nuclear waste repository, undrained straight shear test on constant volume saturated bentonite were carried out, research in 25, 40, 60℃ temperature, NaOH, KOH solution on the shear resistance of compacted bentonite, with the help of SEM microscope test to analyze bentonite microscopic morphological changes, and explore the mechanism of its action. The results show that the shear stress of bentonite samples in the temperature-alkali environment is relatively stable and all of them show strain softening characteristics. the concentration was increased from 0.1 mol/L to 1.0 mol/L, and the temperature was increased from 25℃ to 60℃, the shear stress and shear strength of bentonite were enhanced, along with the cohesion and internal friction angle; the increase in solution concentration would aggravate the degree to which cations would reduce the repulsive force between the particles of the soil body and alters the microstructural arrangement of particles; The increase in temperature increases the activity of water molecules, which reduces the weakly bound water between soil particles and increases the strength of the shrinkage skeleton of the crystal layer, in addition to promoting the reaction between the alkali solution and the soil particles, which leads to an increase in the cohesion and the angle of internal friction. Cation exchange reaction between different alkali solutions, resulting in K+ and bentonite to produce a higher strength of the K-linkages, so that under the same conditions of KOH solution on the bentonite shear stress and shear strength to improve the degree stronger than NaOH solution, bentonite cohesion and the angle of internal friction is also produced to improve. |
