Experimental study of one-dimensional compression creep in crushed dry coral sand

Abstract

Understanding the time-dependent deformation behaviour of backfill coral sand is important to the long-term stability of engineering facilities built on reefs and reclaimed land. A series of one-dimensional compression tests (with no lateral strain) were carried out on crushed coral sand with a variety of grading and relative densities (50%, 70%, and 90%) sampled from the South China Sea. Axial pressure was applied in stepped loading form: 100, 200, 400, 800, and 1600 kPa. Each level loading was applied for 3 days and then completely unloaded until the deformation was stable, after which the next loading level was applied. The test results indicate: (i) the deformation of coral sand is much larger than silica sand and involves a larger proportion of time-dependent and plastic deformation; (ii) the total deformation of coral sand and proportion of irreversible deformation decreases as the relative density increases; (iii) coral sands of better grading tend to deform less in total and have larger proportions of elastic and time-dependent deformation; and (iv) the grading of coral sand changes during the deformation process due to particle breakage. Based on the test results, the relationships between particle breakage and pressure, relative density, and grading, as well as the grain-scale mechanism of the deformation, are discussed.