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<p>Deep soil mixing (DSM) is a prominent ground improvement method. While field tests are the most reliable means of assessing the strength of DSM columns, their high costs and long durations pose significant challenges. To overcome these challenges, some researchers have developed laboratory-scale DSM setups; however, a standardized protocol for such setups is currently lacking. Therefore, this study first reviews existing devices and introduces an apparatus constructed in this investigation to enhance understanding of laboratory DSM methodologies. It is important to note that the use of these devices does not imply permission to abandon large-scale field experiments, and they will remain crucial. The research further examines how soil bed moisture content (<i>ω</i>) affects the mixing quality of DSM columns, along with the impacts of cement dosage (<i>α</i>) and total water-to-cement ratio (<i>W</i><sub><i>Total</i></sub><i>/C</i>) on strength characteristics. For this purpose, a series of small-scale DSM columns with a diameter of 100&#xa0;mm and a depth of 600&#xa0;mm were constructed in sand beds with <i>ω</i> levels of 0%, 5%, and 30%, representing dry, moist, and saturated conditions, respectively, with varying <i>W</i><sub><i>Total</i></sub><i>/C</i> ratios (2.5, 3.0, and 3.5) and <i>α</i> values (300, 400, and 500&#xa0;kg/m<sup>3</sup>). Unconfined compression tests (UCT), optical microscopy (OM), and scanning electron microscopy (SEM) were employed for assessments. Findings revealed that in dry and moist beds, slurry water within the DSM columns migrated into the surrounding soil, resulting in a significant decline in both mixing quality and strength of the columns. Conversely, in the saturated bed, the surrounding soil’s water content effectively prevented slurry water from escaping, thereby mitigating the adverse effects observed in the dry and moist beds. Results demonstrated that unconfined compressive strength (UCS) and secant modulus (<i>E</i><sub><i>50</i></sub>) exhibit direct and inverse relationships with <i>α</i> and <i>W</i><sub><i>Total</i></sub><i>/C</i>, respectively. Since these correlations were consistent across all columns installed with different <i>W</i><sub><i>Total</i></sub><i>/C</i> ratios and <i>α</i> values, it is concluded that <i>α</i> and <i>W</i><sub><i>Total</i></sub><i>/C</i> independently influence UCS and <i>E</i><sub><i>50</i></sub>.</p>

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Construction of a DSM Apparatus to Evaluate the Effects of Soil Bed Moisture Content, Cement Dosage, and Total Water-to-Cement Ratio on Mixing Quality and Strength of DSM Columns

  • 期刊论文

  • 发表日期：

    2025年8月20日

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  • Mahdi Safdari Seh Gonbad,
  • Mahmood Reza Abdi

摘要

Deep soil mixing (DSM) is a prominent ground improvement method. While field tests are the most reliable means of assessing the strength of DSM columns, their high costs and long durations pose significant challenges. To overcome these challenges, some researchers have developed laboratory-scale DSM setups; however, a standardized protocol for such setups is currently lacking. Therefore, this study first reviews existing devices and introduces an apparatus constructed in this investigation to enhance understanding of laboratory DSM methodologies. It is important to note that the use of these devices does not imply permission to abandon large-scale field experiments, and they will remain crucial. The research further examines how soil bed moisture content (ω) affects the mixing quality of DSM columns, along with the impacts of cement dosage (α) and total water-to-cement ratio (WTotal/C) on strength characteristics. For this purpose, a series of small-scale DSM columns with a diameter of 100 mm and a depth of 600 mm were constructed in sand beds with ω levels of 0%, 5%, and 30%, representing dry, moist, and saturated conditions, respectively, with varying WTotal/C ratios (2.5, 3.0, and 3.5) and α values (300, 400, and 500 kg/m3). Unconfined compression tests (UCT), optical microscopy (OM), and scanning electron microscopy (SEM) were employed for assessments. Findings revealed that in dry and moist beds, slurry water within the DSM columns migrated into the surrounding soil, resulting in a significant decline in both mixing quality and strength of the columns. Conversely, in the saturated bed, the surrounding soil’s water content effectively prevented slurry water from escaping, thereby mitigating the adverse effects observed in the dry and moist beds. Results demonstrated that unconfined compressive strength (UCS) and secant modulus (E50) exhibit direct and inverse relationships with α and WTotal/C, respectively. Since these correlations were consistent across all columns installed with different WTotal/C ratios and α values, it is concluded that α and WTotal/C independently influence UCS and E50.