Three-dimensional swelling pressure and chemical influence on deformation of a compacted bentonite

An experimental study was carried out on compacted samples of GMZ001 bentonite. Characteristics of three-dimensional swelling pressure of GMZ001 bentonite was researched using a 3D swelling-shrinkage apparatus. Both vertical and horizontal swelling pressure showed exponential functions against their dry density, however, the swelling pressures were independent of initial suction of samples. The ratio of horizontal swelling pressure to vertical swelling pressure decreased with increasing dry density. The influence of dry density and soaking liquid on swelling of bentonite was examined, and the swelling deformation was noticeably effected by all these factors. An investigation of the chemical deformation induced by changing soaking liquid was also attempted. The samples dilated when the soaking liquid changed from the sodium chloride solution to the distilled water, while they shrunk when the soaking liquid changed from the distilled water to the sodium chloride solution. However, an initial collapse, after changing the soaking liquid to distilled water, was observed for a sample with the lower initial dry density and ever soaked in the higher salinity solution. The swelling deformation obtained for the samples soaked directly in distilled water was larger than that immersed first in NaCl solution and then in distilled water. Complex mechanical responses in chemical cycles were observed.