DFI Technical Committee Project on the Effect of Overburden Stresses (During Curing) on the Mechanical Properties of Soil-Cement Mixed Materials-PPT Presentation

PPT Presentation

Pdf Summary

The DFI Technical Committee study examined how overburden stress during curing affects the strength of deep-mixed soil-cement materials. Researchers combined laboratory bench tests, modified oedometer tests, field oedometer testing, independent core data, and in-situ instrumentation.<br /><br />The results indicate that curing under overburden stress can increase unconfined compressive strength (UCS). Strength gains were generally related to the applied stress and soil type, and an empirical coefficient, α, was proposed to estimate in-situ strength. Comparisons with field core data suggest the coefficient provides reasonable predictions for most soils.<br /><br />Fine-grained soils generally showed greater strength gains than granular soils. In the laboratory, strength for low-plasticity clayey silt and silt soils was substantially more responsive than for poorly graded sand. Highly plastic clays were the key exception: they showed little or no strength gain, likely because their low permeability restricts drainage during curing.<br /><br />The proposed explanation is that drainage and consolidation reduce void ratio and promote particle reorientation. This can increase particle contact and chemical bonding; soils with greater specific surface area may also provide more bonding sites. In-situ instrumentation suggests a hydraulic connection between deep-mixed columns and the surrounding water table, supporting the role of drainage.<br /><br />Overall, overburden curing stresses influence deep-mixed material strength, and the effect can generally be quantified based on soil type, except in highly plastic clays where drainage is limited.

Keywords

overburden stress

curing

deep-mixed soil-cement

unconfined compressive strength

UCS

oedometer tests

soil type

fine-grained soils

drainage and consolidation

empirical coefficient alpha