Investigating the pore-water chemistry effects on the volume change behaviour of Boom clay

Boom clay samples were taken from the borehole drilled in Essen site to characterise the Hydro-mechanical behaviour of Boom clay in the Belgian program for nuclear waste disposal. Owing to its geographical situation closer to the sea, Boom clay at Essen presents a pore water salinity 4–5 times higher than Boom clay at Mol. This study aims at studying the effects of pore water salinity on the hydro-mechanical behaviour of Boom clay. Specific oedometer cells were used allowing ‘‘flushing’’ the pore water in soil specimen by synthetic pore water or distilled water. Mechanical loading was then carried out on the soil specimen after flushing. The results show that water salinity effect on the liquid limit is negligible. The saturation or pore water replacement under the in situ effective stress of 2.4 MPa does not induce significant volume change. For Ess83, hydro-mechanical behaviour was found to be slightly influenced by the water salinity; on the contrary, no obvious effect was identified on the hydro-mechanical behaviour of Ess96. This can be attributed to the higher smectite content in Ess83 than in Ess96.