上海浅部黏土渗透系数及其各向异性

为研究上海浅部黏土的渗透系数及其各向异性，沿水平及竖直方向对上海浅部主要黏土层进行了不同压力下的固结试验，联合使用时间平方根法和时间对数法获取了试样的渗透系数，探讨了渗透系数与孔隙比及渗流方向之间的关系，并通过电镜扫描，从微观角度分析了水平和竖直方向渗透系数存在差异的原因。研究结果表明：上海浅部主要黏土层的渗透系数均随着孔隙比的增加而增大。对于单组试验来说，渗透系数k与孔隙比e在e lgk坐标系中呈现很好的线性关系，且渗透变化指数Ck大致呈现Ck = 0.5e0的规律；但对于整体试验而言，渗透系数与孔隙比在e lgk坐标系中大致呈现出曲线关系。通过扫描电镜观察，揭示了沉积形成的絮状微观结构是竖直和水平渗透系数差异较小的主要原因。

Permeability and anisotropy of upper Shanghai clays

To study the permeability and anisotropy of upper Shanghai clays, oedometer tests were carried out under different pressures in both horizontal and vertical directions. Permeability was determined by the square root of time method and log time method, and the relationships between coefficient of permeability and void ratio and the flow direction were discussed. The reason of the difference in the horizontal and vertical permeability coefficients is analyzed on the microscopic level by using scanning electron microscope. Results reveal that the coefficient of permeability of upper Shanghai clays increases with the increase of void ratio. For a single test, the relationship between coefficient of permeability and void ratio is linear in e-lgk coordinate system and the permeability change index is roughly Ck=0.5e0. For all tests, the relationship between coefficient of permeability and void ratio is curved in e-lgk coordinate system. Anisotropy of upper Shanghai clays under different pressure conditions is not obvious, which is related to the formed flocculent structure in the process of soil particle deposition. In other words, the difference of the pore content in the horizontal and vertical directions leads to the anisotropy in the coefficient of permeability.