Laboratory model of soil humidification in unsaturated area after vacuum preloading treatment

The vacuum preloading treatment creates an unsaturated zone in the upper layer of soft soil. After the vacuum pressure is released, groundwater outside the reinforced area will seep in, gradually wetting the unsaturated zone and leading to a decrease in soil strength and an increase in deformation. Based on indoor model tests, the analysis of the conditions of wetting in the reinforced area due to external recharge water after the vacuum extraction was conducted by examining settlement deformation, pore water pressure, moisture content, saturation degree, and undrained shear strength of the reinforced soil. The results indicate that settlement rebounds, with deformation first increasing slowly, then rapidly, and finally stabilizing at a slow growth rate; pore water pressure shows a trend of increase over time; moisture content of the soil has increased, with smaller changes in moisture content at greater depths; the upper unsaturated zone of the soil becomes partially saturated after wetting, and the undrained shear strength at a depth of 0.25 m varies significantly with different distances from the recharge water source, ranging from a minimum of 64.8 kPa to a maximum of 90.1 kPa; at a depth of 0.50 m, the differences in undrained shear strength with varying distances from the recharge water source are minor, ranging from a maximum of 66.8 kPa to a minimum of 64.9 kPa. The wetting conditions of the soil are related to the distance from the recharge water source; the closer the distance to the recharge water source, the greater the impact of wetting, providing reference for practical engineering.