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Abstract 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.
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Received: 25 February 2010
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