Mechanism Explanation of Influence of Dry Density and Water Content on Bentonite Swelling Process

The swelling process of bentonite is vital for judging the time required for completing the swelling, estimating the engineering safety, and organizing the construction plan. Many factors affect the swelling process, and the underlying mechanisms still require to be clearly explained. In this paper, the swelling process of commercial bentonite in different molar concentrations of salt solution was studied by the one-dimensional free swelling test and constant volume swelling pressure test. The curves of swelling over time were fitted using a hyperbolic model, and two parameters were extracted to reflect the swelling rate and the final swelling strain or swelling pressure quantitatively, respectively. The test results show that the final swelling strain or swelling pressure is determined by the swelling ability of the bentonite, while the swelling rate is influenced by the coupled effect of the swelling ability and permeability of soil. The mechanisms of different factors affecting the swelling process of bentonite are summarized as the effects on the permeability and swelling ability of the soil by considering the change process of pore structure during swelling. The proposed mechanism explanation can also reasonably explain the effect of initial water content in the existing literature. The influencing mechanism of the swelling process revealed in this paper from the perspective of pore structure provides a reasonable theoretical basis for analyzing the swelling process of bentonite.