Abstract: Coral islands and reefs are always in a complex marine dynamic environment. Seepage deformation or even damage of foundation of embankment cofferdam, foundation pit and other structures on the island will increase the possibility of subsoil bearing capacity failure. In order to explore the permeability and consolidation of calcareous sand mixed with rubber fiber, constant head permeability test and consolidation test were used to study the permeability and consolidation deformation of calcareous sand with different fiber contents, and the control group containing fiber glass beads was set. Calcareous sand has extremely irregular particle shape, ultra-high non sphericity and abnormal rich edges and corners, further study was carried out by a high-speed dynamic image particle size analyzer to analyze the particle shape and size of the calcareous sand and glass bead. The test results show that the fiber content hardly affect the permeability of calcareous sand samples, but the permeability coefficient first increases and then decreases with the increase of fiber content in the glass beads containing fiber. To some extent, the addition of rubber fiber shortens the water passage in the calcareous sand sample. Calcareous sand sample has a pressure threshold of 800 kPa. When the pressure exceeds 800 kPa, the increase of compression modulus slows down. The e-lg p curve of the mixture sample with different fiber contents can be expressed by the Harris model. The material coefficient of the calcareous sand-rubber fiber mixture is C=5, and that of the glass bead-rubber fiber mixture is C=3. Meanwhile, there is a good linear relationship between material parameters a and b and fiber content.

Key words: calcareous sand, permeability coefficient, consolidation characteristics, rubber fiber