天然沉积饱和黏土渗透系数试验研究与预测模型

Experimental study of permeability coefficient of natural saturated clay and its prediction model

为研究天然沉积土的物理特性、结构状态与应力水平对其渗透特性的影响,采用固结渗透联合试验,对太湖湖沼相粉质黏土原状样与具有不同前期固结压力的重塑样的渗透系数变化规律进行了测定。原状样和重塑样的渗透系数均随固结压力的增大呈非线性减小,且两者的孔隙比与渗透系数的变化模式相一致;而前期固结压力仅影响渗透系数大小。试验结果表明:土体渗透系数随孔隙比的变化规律不受土结构性(颗粒间胶结作用)和应力历史的影响;对于同一土体,渗透系数大小主要由孔隙比决定,进而对试验和相关文献中不同土体渗透系数在压缩过程中变化规律进行了分析,建立了线性的lg(1+e)-lgkv渗透模型,并考虑了液限的影响,对渗透指数k C的经验关系进行了修正,修正后的k C计算结果更接近于实测值。研究结果对准确分析原位地基实际受荷过程中非线性固结性状具有重要意义。

In order to explore the effect of physical properties, structural conditions and stress level on the permeability characteristics, consolidation-permeability tests are adopted to investigate the change of permeability coefficient during compression of Taihu swamp undisturbed silty clays and remolded samples experienced different preconsolidation pressures. The experimental results show that the permeability coefficient decreases nonlinearly with increasing consolidation pressure, and the relationship between void ratio and permeability coefficient of undisturbed specimen is almost identical to that of the remolded specimen, which is not influenced by the inter-particle cementation and stress history. For the same soil, the magnitude of permeability coefficient is mainly governed by the size of soil pore. Furthermore, according to the analysis results of the variation mode of permeability coefficient during compression tests in this work and related literatures, the linear lg（l＋e）-lgkv permeability model is presented, and the empirical relationship of the permeability index is modified by considering the liquid limit. Using the modified expression, the calculation results of the permeability index agree well with the tested values. This study has important significance in accurately analyzing the nonlinear consolidation behavior of saturated clay foundation subjected to time-dependent loading.