极细颗粒黏土渗流特性试验研究

EXPERIMENTAL STUDY OF SEEPAGE CHARACTERISTICS OF TINY-PARTICLE CLAY

为深入研究极细颗粒黏土的渗流特性,采用可调节水头高度的常水头渗透试验装置,利用不同离子浓度的孔隙液和蒸馏水,分别对极细颗粒人工土和广州南沙天然软土进行渗透试验。试验结果显现土体渗流的2个重要的特性,一是随着孔隙液离子浓度的增大,试样的渗透系数随之增加;二是随着水力梯度的降低,对于不同离子浓度的孔隙液情况,试样的渗透系数出现增大或者减小的"异常"现象。试验结果和机制分析认为,土颗粒表面电荷的微电场作用和渗流孔隙的微尺度效应是影响极细颗粒黏土的渗流特性的重要原因,而颗粒比表面积、表面电位、孔隙液离子浓度和孔隙尺度则是改变渗流特性的重要影响参数。对上述2个渗流特性分别采用"微电场效应"和"微尺度效应"作出解释,其中对软土渗流"异常"现象的真实原因仍需要更多的试验和进一步的研究探讨。

For further study of the seepage characteristics of tiny-particle clay,variable height and constant-head seepage apparatus are adopted to conduct experiments on tiny-particle artificial soil and natural soft soil from Nansha of Guangzhou with pore water of different ion concentrations and distilled water.The test results show two important characteristics of soil seepage.First,the permeability coefficient increases with the increase of ion concentration of pore water.Second,the permeability coefficients of the samples with pore water of different ion concentrations show abnormal increase or decrease trends with the reduction of hydraulic gradient.The analyses of results and mechanism suggest that the micro-electric field effect caused by surface charge on clay particles and microscale effect of seepage pore are the main reasons that influence the seepage characteristics of tiny-particle clay;and the particle specific surface area,surface potential,ion concentration of pore water and pore scale are important influence parameters that lead to the change of seepage characteristics.Micro-electric field effect and microscale effect are adopted to explain the two seepage characteristics mentioned above.However,more experiments and research are needed to study the real causes of the abnormal soil seepage phenomenon.