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<p>In field cases, the methodological workflow of deep soil mixing (DSM) projects involves many trial-and-error steps due to the large number of parameters that influence the process. Furthermore, the difference between the strength of laboratory mix samples and DSM columns installed in the field ranges from 20% to 100%. This situation complicates the installation procedure of DSM columns and quality control/quality assurance stages. Moreover, excessive use of cement causes environmental concerns. This research aims to address these issues by producing silica fume replaced cement DSM samples in clay using a laboratory mixer (small-scale, SS-DSM samples) and a prototype DSM machine (large-scale, LS-DSM samples). The mechanical and microstructural characteristics of DSM samples were investigated through strength, permeability, SEM, and XRD tests. Test results were analyzed using Response Surface Methodology, variance analysis (ANOVA), and multi-response optimization methods. An increase in binder dosage, binder content, and curing time improved the performance of the DSM samples, whereas an increase in the water/binder ratio led to a decrease. The optimum mix proportions were 20% cement, 15% silica fume, 1.2% superplasticizer, water/binder ratio of 0.9, and soil water content of 25%. Silica fume serves as a sustainable cement replacement and a performance enhancer, effective up to a 42.9% replacement ratio in both SS-DSM and LS-DSM samples. In the LS-DSM samples, strength values were 28.1% lower, and permeability coefficient values were 100.1% higher compared to the SS-DSM samples. This is primarily attributed to the 40.4% lower binder content (<i>a</i><sub><i>w</i></sub>) and the 28.8% higher total water-to-binder ratio (<i>W</i><sub><i>T</i></sub>:<i>W</i><sub><i>B</i></sub>) in the LS-DSM samples relative to the small-scale ones. To minimize the discrepancy between SS-DSM and LS-DSM samples, soil-slurry mixtures should be prepared based on binder content rather than binder dosage. The binder contents in SS-DSM and LS-DSM samples relate as <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\:{\left({a}_{w}\right)}_{LS}={\left({a}_{w}\right)}_{SS}\cdot\:(1-VR)\)</EquationSource> </InlineEquation>, where VR is the volume rate of the slurry to the mixture. SEM and XRD test results confirm the performance improvement of the DSM samples.</p>

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Scale effect on the strength and permeability of cement-silica fume deep mixing columns: Laboratory mixer vs. prototype DSM machine

  • 期刊论文

  • 发表日期：

    2026年6月30日

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  • Yavuz Yenginar,
  • Mustafa Abdalwahid Noori Noori,
  • Murat Olgun

摘要

In field cases, the methodological workflow of deep soil mixing (DSM) projects involves many trial-and-error steps due to the large number of parameters that influence the process. Furthermore, the difference between the strength of laboratory mix samples and DSM columns installed in the field ranges from 20% to 100%. This situation complicates the installation procedure of DSM columns and quality control/quality assurance stages. Moreover, excessive use of cement causes environmental concerns. This research aims to address these issues by producing silica fume replaced cement DSM samples in clay using a laboratory mixer (small-scale, SS-DSM samples) and a prototype DSM machine (large-scale, LS-DSM samples). The mechanical and microstructural characteristics of DSM samples were investigated through strength, permeability, SEM, and XRD tests. Test results were analyzed using Response Surface Methodology, variance analysis (ANOVA), and multi-response optimization methods. An increase in binder dosage, binder content, and curing time improved the performance of the DSM samples, whereas an increase in the water/binder ratio led to a decrease. The optimum mix proportions were 20% cement, 15% silica fume, 1.2% superplasticizer, water/binder ratio of 0.9, and soil water content of 25%. Silica fume serves as a sustainable cement replacement and a performance enhancer, effective up to a 42.9% replacement ratio in both SS-DSM and LS-DSM samples. In the LS-DSM samples, strength values were 28.1% lower, and permeability coefficient values were 100.1% higher compared to the SS-DSM samples. This is primarily attributed to the 40.4% lower binder content (aw) and the 28.8% higher total water-to-binder ratio (WT:WB) in the LS-DSM samples relative to the small-scale ones. To minimize the discrepancy between SS-DSM and LS-DSM samples, soil-slurry mixtures should be prepared based on binder content rather than binder dosage. The binder contents in SS-DSM and LS-DSM samples relate as \(\:{\left({a}_{w}\right)}_{LS}={\left({a}_{w}\right)}_{SS}\cdot\:(1-VR)\) , where VR is the volume rate of the slurry to the mixture. SEM and XRD test results confirm the performance improvement of the DSM samples.