In the deposition process

the calcareous sand

mostly retaining tiny pores of the protozoan skeleton

shows hierarchical porosity

irregular shape

high angular edge

low strength and fragile

cemented property of particles. Therefore calcareous sand are different from general terrestrial and marine sediments in its engineering properties especially the permeability due to the hierarchical porosity and highly-irregular shape. In this study

the double-ring permeation experiments are carried out to analyze the effect of density and particle size on the permeability of calcareous sand. Test results show that the seepage rate of calcareous sand increases gradually and then stabilizes within a range of small fluctuation. The permeability coefficient of calcareous sand is negatively correlated with the nonuniformity coefficient Cu. As the inflection points of particle-size distribution curve become smaller than effective diameter d10 appear near the weight-accumulative 4% percent diameter d4 of soil

the ratio of d4 to constrained diameter d60 is adopted to analyze the relationship between the dry density and the permeability of calcareous sand. An exponential function is fitted between permeability coefficient with dry density and compaction degree . The fitting exponential function of the calcareous sand permeability coefficient is or . If the values of Cu≤5

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