Abstract: Calcareous sand is a type of marine biogenic sand, which is the main material for the hydraulic filling of islands and reefs in the South China Sea. Studying dynamic characteristics of calcareous sand is of great significance to the development and utilization of resources in the South China Sea. In actual engineering, calcareous sand is mainly affected by wave loading that changes both in amplitude and principal stress direction. The effect of wave loading is quite different from that of fixed principal stress axes loading. Therefore, torsional shear apparatus that can simulate wave loading are used to carry out a series of undrained tests on saturated calcareous sand, mainly to study the influences of cyclic stress ratio (CSR) and relative density (D_r) on the characteristics of pore water pressure. The results are further compared with quartz sand, finding that differences in particle shape leads to the different pore water pressure development patterns between calcareous sand and quartz sand. In addition, the energy method is introduced to preliminarily examine the development of accumulated energy loss. On the basis, a model considering different relative densities is established to describe the relationship between pore water pressure and accumulated loss energy.

Key words: wave loading, calcareous sand, characteristics of pore water pressure, accumulated loss energy