Abstract: Electrical conductivity is a direct measurable parameter reflecting the soil and water coupling properties of the island, and permeability coefficient play an inportant role on formation of underground freshwater; so it is of great significance to study the variation law of electrical conductivity under different geological conditions and to characterize the permeability of soil. Firstly, the conductivity of single size calcareous sand is measured in different dry densities, water contents and solution concentrations. Because calcareous silt contains clay, its surface electric double layer has influence on conductivity. Therefore, the conductivity of calcareous silt under the condition of orthogonal dry density and moisture content is measured separately, and the variable head permeability test is carried out. Secondly, graded soils with increasing content of calcareous silt are prepared, their conductivities are measured companied by constant head permeability test. The results show that there exist relationships between the conductivity and the dry density, water content and solution concentration. Conductivity of calcareous soil increases slowly first, then quickly, and finally trends to steady with the increasing of silt content. Permeability of mixed soil decreases slowly first, then rapidly with the increase of conductivity. The permeability coefficient of silt increases with the increase of electrical conductivity, showing a law of large in medium stage and small in initial and final stages. Finally, empirical formulas of conductivity and permeability coefficient of calcareous soil are deduced preliminarily.

Key words: calcareous sand, conductivity, permeability, coefficient clay, double electric layer