基于有效孔隙比的黏性土渗透系数经验公式研究

EMPIRICAL FORMULAS OF PERMEABILITY OF CLAY BASED ON EFFECTIVE PORE RATIO

粗粒土的渗透系数可由与渗透性能相关且较易量测的常规参数估算,研究黏性土的类似经验公式具有重要的理论意义。首先考虑结合水膜对黏性土渗透特性的影响,定义黏性土的无效孔隙比和有效孔隙比的概念,利用黏性土的稠度界限指标液限、渗流的起始水力坡降和双电层参数3种方法,推导无效孔隙比和有效孔隙比的计算公式,然后对常用的粗粒土渗透系数经验公式进行修正,得出适用于黏性土的渗透系数经验公式。最后选取泾阳黄土、南海软黏土和科威特盐渍土的相关物理参数,分别代入粗粒土和黏性土的渗透系数经验公式中,得到渗透系数的计算值,将其与室内试验的实测值进行对比,验证黏性土渗透系数经验公式的合理性。在比较分析渗透系数经验公式及3种有效孔隙比计算方法的优缺点后,推荐采用稠度指标法修正的柯森–卡门和斯托克斯经验公式作为黏性土渗透系数的计算公式。

The permeability of coarse-grained soil can be calculated using the easy-measured and conventional parameters. The similar empirical formula for clay is the focus of this paper. The invalid and the efficient void ratios were defined considering the influence of the adsorbed water layer on the permeability characteristics of clay. The formulas of the invalid and the efficient void ratios were derived with three methods,e.g.,the liquid limit,the initial hydraulic gradient and the double electric layer parameters of clay. The empirical formulas of permeability coefficient of clay were obtained by modifying the empirical formulas of permeability coefficient for sand. Substituting the relevant physical parameters of the loess from Jingyang,the soft clay in the south China sea and the coastal saline soil of Kuwait into the empirical formulas of permeability for sand and clay respectively yielded the values of the coefficient of permeability. Comparison of the calculated and the measured values confirmed the reasonableness of the empirical formulas of permeability coefficient for clay. The Kozeny-Carman and Stokes empirical formulas modified with the method of consistency index were recommended by comparing the advantages and disadvantages of the empirical formulas and the three methods.