黏粒含量对粉质黏土土水特性影响的试验研究

Experimental Study on Impacts of Clay Content on Soil-Water Characteristics of Silty Clay

粉质黏土分布广泛,其土水特性受黏粒含量影响显著。为揭示黏粒含量对粉质黏土土水特性的影响规律,采用离心机对不同黏粒含量粉质黏土进行脱水条件下土水特性测试试验。首先,制备六组干密度相同的不同黏粒含量粉质黏土试样,并通过密度计与筛分联合测定法获得试样颗粒级配曲线和黏粒含量。然后,通过调节离心机转速得到不同基质吸力对应的土样总质量与含水量,并基于Van-Genuchten模型拟合土样土-水特征曲线,进而分析黏粒含量对土-水特征曲线的影响。研究结果表明:(1)不同黏粒含量粉质黏土的体积含水率均随基质吸力增加逐渐减小且变化趋势基本一致:当基质吸力小于20 k Pa时,含水率接近饱和含水率,大于20 k Pa后含水率随基质吸力增加快速减小;(2)黏粒含量越高,粉质黏土持水能力越强,土体含水率越大,含水率受黏粒含量增加影响的程度呈现先增大后减小的趋势;(3)相同基质吸力条件下,黏粒含量越高,土体含水率越大,在基质吸力大于80 k Pa后不同黏粒含量土样的含水率相差越来越小;(4)残余含水率偏高,吸附的水分仍达到其饱和状态含水量的40%左右。这为进一步进行非饱和粉质黏土软基的水力特性评估提供了技术支持。

Silty clay is very common in geotechnical engineering and its soil water characteristics are affected by clay contents.To disclose the impacts of clay content on soil-water characteristics of silty clay,centrifuge tests for soil-water characteristics with silty clay samples of different clay contents were performed.Firstly,six silty clay samples with different clay contents and the same dry density were prepared and their particle size distributions and clay contents are determined with the densimeter method and the sieving method.Then,the corresponding soil moistures and weights of different matrix suctions are obtained by adjusting the speed of a centrifuge,and soil-water characteristic curves of six samples are fitted on Van-Genuchten model.The results show as follows.①The volumetric moisture contents of the clay with different clay contents decrease with the increase of matrix suction and their trends are the same:the volumetric moisture content varies little when the matric suction is less than 20 kPa,which is close to the saturated water content,but decreases rapidly with the increase of matrix suction when the matrix suction is greater than 20 kPa.②The higher the content of clay particles,the stronger the water retention capacity and saturated moisture content of silty clay,the greater its water content,as the clay content increases,the influence of clay content on moisture content first increases and then diminishes.③The large clay content corresponds to large water content of volume in the case of same soil suction,the volumetric moisture contents of silty clay with different clay contents vary smaller and smaller after the matrix suction is more than 80 kPa.④The residual moisture content of silty clay is relatively higher,the residual moisture absorbed still reaches 40%of its saturated state.This provides a technical supporting for further evaluation of hydraulic and mechanical characteristics of unsaturated silty clay ground.