Determining the Effects of Operational Parameters and Geotechnical Conditions on the Behavior of Soil–Cement Columns Using a Small-Scale Physical Model in Sandy Soil

The behavior of jet grouting columns is influenced by several operational and geotechnical parameters, but relatively little attention has been paid to the significance of the initial soil moisture content on the columns. In the current study, a small-scale jet grouting device has been used to create 47 small-scale columns in dry and wet (20% moisture content) sand to investigate the effects of the soil moisture content on the diameter, uniaxial compressive strength (UCS), and the treatment efficiency. The columns were constructed using different injection times, rotational speeds of 10 and 25 rpm, and soil relative densities of 5% and 95% to assess the comparative influence of the moisture content on the effectiveness of other parameters. The results demonstrated that the initial soil moisture had the most significant effect on the column diameter. In sand with a 20% moisture content, the column diameter increased an average of 63% and 87% in loose and dense sand, respectively, compared to dry sand. However, an increase in the injection time in wet sand caused a significant decrease in the treatment efficiency. A 60% decrease in the rotational speed from 25 to 10 rpm had a greater effect on increasing the diameter in dry sand than doubling the injection time. The relative density had a much smaller effect on the column diameter created in wet sand than in dry sand. The high cement-to-soil ratio of the columns increased the UCS of the core samples and eliminated the effect of the aforementioned parameters on the UCS.