Bentonite strain due to cyclic suction changes

A series of suction-controlled oedometer tests were performed on a highly compacted bentonite following drying/wetting and wetting/drying paths from the initial hygroscopic conditions (about 120 MPa) under low vertical load. The increase of suction to values of close to 500 MPa induced practically no reduc-tion in volume. During the subsequent hydration, the swelling strains occurring between 500 and 300 MPa were very small, which could be due to plastification of the material on drying, this displacing the elastic range to the interval between those suctions. Afterwards, when suction decreased to the initial value, the ini-tial void ratio was practically recovered and below this value, the reduction in suction did cause a significant increase in volume. In fact, drying did not modify the swelling capacity of the sample during subsequent hy-dration, on the contrary, the deformations observed during wetting were larger in the samples previously dried. In wetting/drying paths the swelling deformation occurred on suction decrease was irreversible and mainly caused by the increase in the microstructural void ratio.Postprint (published version