Laboratory model of soil humidification in unsaturated area after vacuum preloading treatment
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摘要: 真空预压处理软基上部形成非饱和区,真空压力卸载后,加固区外地下水会发生渗流,慢慢湿化非饱和区,造成土体强度降低,变形增大。根据室内模型试验,通过加固土体沉降变形、孔隙水压力、含水率、饱和度及不排水抗剪强度等分析了抽真空结束后外界补给水对加固区湿化的情况。结果表明:土体沉降发生反弹,变形量先缓慢增长,再快速增长,最后缓慢增长至稳定阶段;孔隙水压力随时间呈增长趋势;土体含水率有所增加,土体越深,含水率变化越小;土体上部非饱和区经湿化后部分饱和,且0.25 m深度处与补给水源不同距离土体不排水抗剪强度差别较大,最小处为64.8 kPa,最大处为90.1 kPa;0.50 m深度处与补给水源不同距离土体不排水抗剪强度差别不大,最大处为66.8 kPa,最小处为64.9 kPa。土体湿化情况和与补给水源距离相关,距补给水源越近,湿化产生影响越大,为实际工程提供了借鉴。Abstract: 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.
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Key words:
- vacuum preloading /
- humidification /
- unsaturated region /
- laboratory model experiments
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表 1 土样的物理力学指标
Table 1. Physical and mechanical properties of soil samples
指标 含水率
w/%液限
wL/%塑限
wP/%密度
ρ/(g×cm−3)内摩擦角
φ/(°)黏聚力
c/kPa土粒比重
Gs孔隙比
e压缩系数
av/ MPa−1固结系数
Cv/(cm2×s−1)渗透系数
k/(cm×s−1)泊松比
ν参数值 55.0 49.0 27.0 1.92 19.8 4.2 2.72 1.16 0.87 2.0×10−4 1.2×10−6 0.33 表 2 湿化后与补给水源不同距离、不同深度土的饱和度
Table 2. Saturation of soils at different depths and distances after wetting with various supply water sources
深度/m 饱和度/% 距离0.4 m 距离0.8 m 距离1.2 m 距离1.6 m 0.05 90.71 86.88 75.11 72.85 0.15 100 98.03 81.08 75.59 0.25 100 100 95.45 91.71 0.40 100 100 100 100 0.60 100 100 100 100 -
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