This study starts from a question: How would initial water content (wi) affect equilibrium swelling pressure (peq) of compacted bentonites in swelling pressure tests (ps tests)? However, discussions, based on experiments of a bentonite, Kunigel V1 (K_V1), are extended to issues: 1) wi effect on peq, 2) pore water density (ρpw), 3) co-existence of crystalline and osmotic swelling, and 4) relation between peq and compaction tests (pc tests). It is revealed that wi has insignificant effect on peq in general, though significant effect may appear for relatively high wi and dry density (ρd) conditions. Two swelling types, crystalline swelling with basal spacing of montmorillonite (d001= 1.0 nm-1.9 nm) and osmotic swelling (d001 ≥ ∼44.0 nm), co-exist in a w range from 36 to 65%. With the fact that ρpw of K_V1 may range from 1.1 to 1.2 Mg/m3, it is expected that crystalline swelling may mainly govern peq in ps tests if the final dry density of a specimen (ρdf) is larger than 1.46 Mg/m3, while osmotic swelling may mainly govern if ρdf <1.05 Mg/m3. Together with results of pc tests, the effect of wi on peq are explained by the proposed conceptual model.
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