内陆河湖相软土土性指标统计特征与竖向变化规律研究

Study on statistical characteristics and vertical change law of soil index for soft soil in the inland fluvial-lacustrine sediments

【目的】内陆河湖相软土易与沿海地区软土混淆,其工程特性及鉴别标准对该类软土地基处理与沉降稳定控制有着重要的指导价值。针对现有内陆河湖相软土鉴别指标及范围不明确、土性指标竖向变化规律研究不足的问题,【方法】以结合大量工程实践收集到的全国不同区域近3000组内陆河湖相软土的土工试验数据为基础,对其土性指标统计特征、鉴别指标及竖向变化规律开展了系列研究。【结果】结果显示:内陆河湖相软土的天然含水率、孔隙比、压缩系数均小于海相软土对应值,而其密度、快剪黏聚力均较海相软土对应值偏大,但总体上仍具有一般软土天然含水率高、密度小、孔隙比大、抗剪强度低的基本特性;天然含水率、孔隙比、塑性指数、压缩模量、压缩系数作为内陆河湖相软土的5项鉴别指标,均服从对数正态分布,并给出了相应的鉴别标准(w≥28.1、e≥0.81、Ip≥11.5、Es≤6.5、α0.1-0.2≥0.23);从土性指标竖向变化规律来看,内陆河湖相软土的天然含水率、孔隙比、压缩系数、塑性指数、塑限、液限总体上随深度呈现先增大后减小的变化趋势,而天然密度、快剪黏聚力、内摩擦角、压缩模量随深度变化的规律为先减小后增大,塑性指数的平均值和标准差随深度呈线性减小的趋势,快剪黏聚力的平均值和标准差随深度呈线性增加的趋势。【结论】结果表明:内陆河湖相软土的土性指标统计特征与沿海地区软土存在一定差异,其力学性质比海相软土稍微偏好,并沿着深度方向具有成层不均匀的特点,研究成果可为该类软土地基处理与沉降控制提供参考。

[Objective]Inland fluvial lacustrine soft soil is easy to be confused with coastal soft soil.Its engineering characteristics and identification criteria have important guiding value for the treatment and settlement stability control of this kind of soft soil foundation.[Methods]Aiming at the problems that the identification index and scope of existing inland fluvial-lacustrine soft soil are not clear,and the research on vertical change law of soil index is insufficient,based on the geotechnical test data collected from nearly 3000 groups of inland fluvial-lacustrine soft soils in different regions of China,a series of studies were carried out on the statistical characteristics,identification indexes and vertical change law.[Results]The statistical result show that the natural moisture content,the void ratio,the compression coefficient of inland fluvial lacustrine soft soil are all less than the corresponding value of marine soft soil,while its density and the quick shear cohesion are higher than the corresponding indexes of marine soft soil,but this type of soft soil still the basic characteristics of general soft soil on the whole,such as higher natural water content,smaller density,larger pore ratio and lower shear strength.As the five identification indexes of inland fluvial-lacustrine soft soil,the natural water content,the void ratio,the plasticity index,the compressive modulus and the compressibility coefficient all obey the log-normal distribution,and the corresponding identification criteria is given(w≥28.1、e≥0.81、I p≥11.5、E s≤6.5、α0.1-0.2≥0.23).From the vertical change law of soil index,the natural water content,the void ratio,the compressibility coefficient,the plastic index,the plastic limit and the liquid limit with depth generally increase first and then decrease,while the natural density,the quick shear cohesion,the internal friction angle and the compressive modulus change with the depth firstly decrease and then increase.On the other hand,the average value and standard deviation of the plasticity index decreased linearly with depth,and the average value and standard deviation of the quick shear cohesion increased linearly with depth.[Conclusion]The result show that the soil index characteristics of inland fluvial-lacustrine soft soil are somewhat different from those of marine soft soil.Compared with marine soft soil,its mechanical properties are slightly more favorable,and it has the characteristics of uneven stratification along the depth direction.The research result can provide references for the treatment and settlement control of this kind of soft soil foundation.