Experiment study on physical properties and motional characteristics of coral sand

Coral sand which mainly exist in tropical ocean environment is chemically composed of CaCO3 and\ud physically composed of debris and skeletal remains of coral reefs and marine lives under dynamic and weathering\ud effects. Due to its particular material composition, particle structure, migration pathway and depositional environment,\ud coral sand has different physical properties and motion characteristics with quartz sand. In this paper, the physical\ud properties such as proportion, porosity, psephicity and fragmentation of coral sand were analyzed, and the motional\ud characteristics in settlement and starting of coral sand were studied by physical model experiment using coral sand from\ud Nansha islands as test material. The results showed that: (1) the physical properties of coral sand show as high grain\ud density, high porosity, poor psephicity and high fragmentation; (2) water filling in the coral sand pore move with the\ud coral sand itself; (3) coral sand particles with large proportion have a lower starting velocity than the calculation value\ud considering the effect of water in the pore; (4) effective specific gravity controlled by the inner-pore volume should be\ud consider in movement of coral sand