Effect of Curing Stresses on the Mechanical Properties of Soil-Cement Mixed Materials-Paper

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The study investigates how confining stress during curing affects the strength of soil-cement materials produced by deep soil mixing. Standard quality-control samples are often cured without confinement, unlike material in the ground, potentially causing laboratory results to underestimate in-situ strength.<br /><br />Researchers developed a field consolidometer to cure wet soil-cement samples under controlled loads while monitoring consolidation. They tested samples from four active project sites, conducted a controlled sand experiment, and compared results with core data from four additional sites and findings from earlier studies.<br /><br />Across the datasets, unconfined compressive strength generally increased with curing stress. In the sand control test, strength rose from 845 psi without confinement to 1,129 psi at 26.5 psi of confinement. The size of the increase depended on soil type: fine-grained soils showed larger relative gains than predominantly granular soils, while mixed soils tended to fall between them.<br /><br />The preliminary findings suggest that testing unconsolidated wet-grab samples can significantly underestimate the strength of treated ground. This may affect design decisions, project costs, schedules, and the amount of treatment needed to meet strength requirements. The authors emphasize that the results are preliminary and that further research is needed to develop reliable relationships between curing stress, soil type, and engineering properties.

Keywords

soil-cement

deep soil mixing

curing stress

confining stress

unconfined compressive strength

laboratory samples

field consolidometer

soil type

ground improvement

engineering properties