Experimental study of initial water content and specimen preparation method effects on Kunigel-V1 bentonite swelling pressures

Abstract

With a newly developed swelling pressure apparatus, swelling pressure tests were conducted to elucidate initial water content and specimen preparation method effects on swelling pressures (swelling pressure evaluation curve and equilibrium swelling pressure) of Kunigel-V1 bentonite. X-ray diffraction (XRD) tests were conducted to investigate the initial water content and specimen preparation method effects on basal spacing, including basal spacings of specimens before and after wetting. Experiments produced the following results. (1) The swelling pressure evaluation curve changed from a line with peak and valley to a line with early-stage steady rise as increasing initial water content. (2) The initial water content and specimen preparation method exerted no apparent effect on the equilibrium swelling pressure. (3) Basal spacing of the specimen before wetting was affected not only by the initial water content but also by the specimen preparation method. (4) The initial water content did not influence the basal spacing of the specimen after wetting. It was only affected by the specimen preparation method. Based on the swelling pressure evaluation curve patterns, swelling mechanisms during saturation for specimens with different initial conditions were discussed. Initial water content and specimen preparation method effects on equilibrium swelling pressure were explained carefully with basal spacings.