Deep geological disposal designs for nuclear waste often include an engineered barrier to protect the waste canisters and prevent leakage . The long - term safety of the re pository relies on studies of the buffer material . Oedometer tests provide values of de sign parameters for numerical simulations. A newly - developed oedometer with automated suction control is presented to assist in the investigation of the coupled hydro - me- chanical - volumetric behaviour of an expansive clay, namely a natural sodium bentonite. The displacement - controlled device was developed to apply suction over a range of 1 0 MPa to 300 MPa using a divided - flow humidity - generator. The device allows the application of combined stress and suction states, and continuous stress paths of constant vo lume, stress or suction. The development of the new oedometer is described. Results obtained during the preliminary tests are evaluated through comparison with experimental data from similar tests found in the literature. The current method benefits from c ontinuous control of suction with servo - control of relative humidity using calibrated capacitance hygrometers. The system self - compensates for minor temper- ature changes and therefore the requirement for thermal insulation is not as crucial as in vapour equ ilibrium methods
