Preliminary study on the creep characteristics of calcareous sand from reclaimed coral reef islands in South China Sea

The construction of a series of reclamation islands on coral reefs in South China Sea is a strategic project of China. These reclaimed lands on the top of coral reefs mainly consist of calcareous sand. Previous studies have confirmed that coral calcareous sand could generate creep deformation under long term constant loading. As the foundation material of all kind of structures built on reclaimed coral reefs, the creep behavior of calcareous sand will definitely affect the long-term subsidence of these structures. Therefore, it is highly necessary to investigate the long-term creep characteristics of the coral calcareous sand from South China Sea. A series of tri-axial drained creep tests were performed with the samples from a coral reef island in South China Sea under the confining pressure of 100 kPa to investigate the creep characteristics of calcareous sand. The experimental results indicate that the creep of the calcareous sand is an attenuated and steady type. The curves between the creep strain and the time in double logarithmic coordinates are all straight lines under different stress conditions and can be described by a power function. It is found that, in the case of the same dry density of the calcareous sand, these straight lines corresponding to different creep deviatoric stresses are basically parallel with each other and the slopes of the straight lines are hardly affected by the creep deviatoric stress. It is also revealed that the trend of volume change of calcareous sand samples at the creep stage is mainly controlled by the process of that the volume contraction of calcareous sand samples is finished or not under shearing before the beginning of the creep stage. The research results show that Mesri creep model can effectively describe the stress-strain-time relation of the coral calcareous sand and that the final creep strain of the calcareous sand is highly linearly related to the stress level q/(σ1-σ3)f. Particles gradation tests before and after the creep test indicate that the creep of the calcareous sand under a low confining pressure is mainly attributed to the slipping, shifting and rearrangement between soil particles. © 2019, Science Press. All right reserved.