Laboratory and Field Verification of Soil-Cement Strength from Deep Mixing In Highly Plastic Cohesive Soils-Paper

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The paper examines how highly plastic clays and organic soils affect the strength and workability of soil-cement produced by deep soil mixing. It emphasizes that soil properties—including organic content, plasticity, initial water content, and sand content—can significantly influence unconfined compressive strength (UCS). In general, higher plasticity, organic content, and water content reduce strength, while greater sand content tends to increase it.<br /><br />The authors recommend a three-phase quality-control program: laboratory testing to classify soils and evaluate trial mixes; installation of calibration columns to verify grout designs and mixing parameters under field conditions; and ongoing production testing with real-time monitoring. Laboratory results can help tailor binder dosages by soil layer, particularly in variable profiles, but cannot reliably predict the exact strength achieved in the field. Field verification is essential because actual mixing conditions differ from bench-scale preparation, and field-cured samples often show higher strengths than laboratory samples.<br /><br />The paper introduces a mixability ratio that accounts for soil plasticity and water added during mixing. In the compiled data, increasing the ratio beyond approximately 2 provided little further benefit to workability or strength. Calibration and production results can guide adjustments to grout water content, specific gravity, binder dosage, and mixing parameters, improving workability while controlling costs.<br /><br />Overall, the authors conclude that established strength correlations are useful for preliminary design, but successful and economical deep mixing—especially in highly plastic or organic soils—depends on site-specific laboratory testing, field calibration, continued production verification, and relevant local experience.

Keywords

deep soil mixing

soil-cement

highly plastic clay

organic soil

unconfined compressive strength

workability

quality control

laboratory testing

field calibration

mixability ratio