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Author: search.filters.author.Chaiyaput, SalisaSubject: search.filters.subject.Clay

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    Partial soil replacement in soil cement using bentonite and polyurethane foam
    (2026-06-01)
    Rattanapitak, Pornkanok
    ;
    Shelina, Aza
    ;
    Ayawanna, Jiratchaya
    ;
    Kingnoi, Namthip
    ;
    Mase, Lindung Zalbuin
    This study evaluates the effects of partially replacing soft clay with Ca-bentonite or polyurethane foam in soil-cement mixtures to improve geotechnical performance in soft soils. Cement content was fixed at 20% by total mix weight (% wt), while soft clay was partially replaced with Ca-bentonite or polyurethane foam at 20% wt, 30% wt, and 40% wt. Density, weight, and compressive strength were evaluated at curing ages of 7 and 28 days. The optimal mixture, determined based on compressive strength, was subsequently selected for the permeability test and compared with natural soft clay and a conventional soil-cement mixture. Moreover, scanning electron microscopy was conducted to characterize particle morphology and pore structure, providing microstructural insight into the strength behaviour of mixtures incorporating both Ca-bentonite and polyurethane foam replacements. The results indicate a clear contrast between the two replacement materials. Ca-bentonite increases density and compressive strength through pozzolanic and filling effects. The optimal sample, consisting of 50% soft clay, 20% cement, and 30% Ca-bentonite (S5C2B3) by weight, achieves a 28-day compressive strength of 9.71 MPa with stiff and brittle behaviours. Weight increase is associated with Ca-bentonite swelling, which enhances impermeability. In contrast, polyurethane foam reduces density and strength, producing a lightweight, ductile material due to its porous structure and water loss. Ca-bentonite is suitable for high-strength or low-permeability applications, whereas polyurethane foam is appropriate for lightweight fill where reduced weight is required.
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    A YIELD FUNCTION AND UNDRAINED BEHAVIOR OF K0 CONSOLIDATED CLAYS
    (2023-01-01)
    Imai, Yoshihito
    ;
    Chaiyaput, Salisa
    ;
    Iinuma, Koichi
    ;
    Akaishi, Masaru
    ;
    Sugiyama, Motohiro
    The Cam Clay model, now sometimes called the classical model, cannot reproduce strain-softening behavior. The minimum principal effective stress σ<inf>3</inf> constant line for K<inf>0</inf> normally consolidated clay is a straight line with slope three in the space of mean effective stress p and axial differential stress q, which is located inside the yield surface in the Cam Clay model. In other words, there is a region in the Cam Clay model where the stress state of normal consolidation is judged to be over-consolidation. In this study, undrained and drained triaxial compression tests were conducted to clarify the problems of the Cam Clay model described above, and an anisotropic yield function was proposed. Results of the consolidated drained triaxial test showed that the plastic strains occurred when the applied minimum principal stress σ3 exceeded the past maximum pressure. This result shows that the yield surface for normally consolidated clay is located near the constant line of the minimum principal effective stress. The void ratio of the clay decreased despite the unloading test into the yield surface of the Cam Clay model, which exhibits elastic behavior. This experimental result can emphasize that the stress change in the yield surface causes plastic strain in the clay. The strain softening behavior can be approximated by the proposed yield function if the degree of strain softening is small.