Features and modelling of time-evolution curves of swelling pressure of bentonite

In order to investigate the shape features of time-evolution curves of swelling pressure of bentonite, a series of swelling pressure tests on GMZ bentonite with different initial dry densities are carried out using the constant volume method. The results show that all the obtained time-evolution curves of swelling pressure are characterized by a typical two-peak shape: as the test starts, the swelling pressure increases sharply to a peak value, followed by decreasing to a valley value, after which it increases again to the final value. It is found that the shape of time-evolution curves of swelling pressure is controlled by 6 parameters: the peak, valley and final values of swelling pressure as well as their corresponding hydration times. According to the formation and development mechanisms of swelling pressure, a predictive model for the time-evolution curve with only 5 parameters is proposed. In this model, the swelling pressure is considered as the superposition result of accumulated and dissipated "wedge" pressures, which are assumed to be related to hydration time through an exponential and a Gaussian distribution function, respectively. The proposed model is verified by the experimental results from this paper and literatures, with satisfactory agreements between the measured results and predicted ones.