On swelling behaviours of a bentonite under different water contents

This study starts from a question: how would initial water content (w i ) affect equilibrium swelling pressure (p eq ) of compacted bentonites in swelling pressure tests (p s tests)? However, discussions, based on experiments of a bentonite, Kunigel V1 (K_V1), are extended to issues: 1) w i effect on p eq , 2) pore water density (ρ pw ), 3) co-existence of crystalline and osmotic swelling, and 4) relation between p eq and compaction tests (p c tests). It is revealed that w i has insignificant effect on p eq in general, though significant effect may appear for relatively high w i and dry density (ρ d ) conditions. Two swelling types, crystalline swelling with basal spacing of montmorillonite (d 001 = 1.0 nm - 1.9 nm) and osmotic swelling (d 001 ≥ ∼4.0 nm), co-exist in a w range from 36 to 65%. With the fact that ρ pw of K_V1 may range from 1.1 to 1.2 Mg/m 3 , it is expected that crystalline swelling may mainly govern p eq in p s tests if the final dry density of a specimen (ρ df ) is larger than 1.46 Mg/m 3 , while osmotic swelling may mainly govern if ρ df <1.05 Mg/m 3 . Together with results of p c tests, the effect of w i on p eq are explained by the proposed conceptual model.