Evaluation and prediction of swelling properties of bentonite under the action of salt solution

Bentonite demonstrates exceptional water absorption and expansion characteristics, along with a high degree of impermeability. The expansion characteristics of bentonite buffer materials are influenced by the underground aqueous solutions containing various base ions. In this paper, the swelling characteristics of bentonite with different dry densities under the action of different base ions and different concentrations of aqueous solution were studied by indoor limited expansion rate and swelling force tests. And the swelling characteristics of bentonite under the action of salt solution were predicted by Back Propagation Neural Network (BPNN). The findings demonstrated that: The swelling process of bentonite can be categorized into four distinct stages: initial swelling, rapid expansion, gradual enlargement, and stable volumetric increase. The expansion rate of bentonite is influenced by the dry density, as well as the type and concentration of the solution. The influence of various solutions on the expansion rate of bentonite follows the order: NaCl < CaCl2 ≈ MgCl2