Abstract: The changes of permeability coefficient and pore structure of clays with high liquid limit and low liquid limit after drying-wetting cycles are compared. For each clay three densities are examined. The results show that after three drying-wetting cycles a larger increase in permeability coefficient is observed in clay with high degree of compaction than that with low degree of compaction when the liquid limits are the same. At the same dry density, the clay with high liquid limit exhibits larger increase in permeability coefficient than low liquid limit clay after drying-wetting circles. During the drying-wetting process, the influence of pore structural damage on permeability coefficient increases as compactness and liquid limit increase. The influence of cracks on permeability coefficient, however, decreases when the compactness increases and the liquid limit decreases. In contrast to low liquid limit clay which does not crack but shrinks after drying-wetting cycles, high liquid limit clay forms significant cracks. The change in permeability coefficient of the samples of the small size is mainly caused by the pore structure, and cannot reflect the influence of cracks. It is suggested that further research on the difference between permeability coefficients of clays with different liquid limits under drying-wetting cycles be carried out through permeability test on site or indoor large-size permeability test.

Key words: landfill, compacted clay, liquid limit, permeability coefficient, pore structure