Effects of Confining Stress During Curing and Shearing on Shear Strength of Lime-Cement Improved Clays-PPT Presentation

PPT Presentation

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The study examines how confining stress during curing and shearing affects the strength of lime-cement improved clay made using the Nordic dry mixing method.<br /><br />In Part I, laboratory-prepared clay from Klett was tested using unconfined compression and triaxial tests. Curing stress increased unconfined compressive strength by about 0.3 times the curing stress, while stress during shearing had a much larger effect—about 1.9 times the confining stress. The results suggest a quasi-preconsolidation pressure of roughly 300–400 kPa. In this case, the strength contribution from curing stress was about one-third of that from stress during shearing.<br /><br />Part II used field samples from Drammen in direct simple shear (DSS) tests. For these very high-strength columns, increasing consolidation stress raised stiffness but had no significant effect on strength. The curing-stress effect was not investigated in this part.<br /><br />Field strengths were 40–250% higher than laboratory strengths, averaging about twice as high. The authors conclude that curing stress may matter for low-strength columns but is negligible for high-strength columns; quasi-preconsolidation pressure can help assess its relevance. DSS is a suitable testing method, and the commonly used estimate of undrained strength as half the unconfined compressive strength is supported. Further research is needed on field testing of dry-mixed columns.

Keywords

lime-cement improved clay

Nordic dry mixing method

confining stress

curing stress

shearing stress

unconfined compressive strength

triaxial tests

direct simple shear

quasi-preconsolidation pressure

undrained strength