INFLUENCE OF CORAL SAND PARTICLE SHAPE ON THE COM￣PRESSION PROPERTY OF COARSE GRAINED CALCAREOUS SOIL

The irregular shape of coral sand particles is a major feature that distinguishes it significantly from the ordinary terrigenous soil. In order to research the influence of coral sand particle shape on the compression property of coarse grained calcareous soil, different coral sand particles(block, branch, rod, flake) were selected manually. Based on the block particles, mixed with any of the other three different shapes of coral sand particles, the different particle shape ratios were controlled to make coarse grained calcareous soil samples, and the indoor compression tests were complete. The particle shape parameters such as roundness, length-width ratio, flatness and convexity of coral sand particles before and after the test were compared and analyzed. The effects of particle shape on the compressibility were evaluated. The test results show that:(1)The compression modulus of coarse grained calcareous soil with diameters of 10~20mm is from 4 to 5.5MPa, and the rebound coefficient is from 42 to 53; (2)With the increase of the amount of branch, rod or flake particles(0, 10%, 20%, 30%), the compressive modulus of the sample changed slightly, and the rebound coefficient continued to decrease. (3)The stress-strain curves of each loading range include one stable point and three sections which are rapid growth stress section, synchronous increase of stress and strain section, strain growth section; (4)With the increase of the amount of branch particles, the length-width ratio and the convexity of the sample increased gradually, while the roundness and flatness were unchanged substantially. Due to the influence of particle breakage, the length-width ratio and flatness of the sample increased after the test, while the roundness and concavity decreased. When selecting coarse grained calcareous soil foundation, its compressibility should be considered to avoid rapid loading at the beginning of construction.