Sedimentary characteristics of coral mud in the South China Sea during the reclamation process

Abstract

Coral mud is a form of calcareous ooze composed of fine-grained coral debris distributed as interlayers due to particle sorting during the formation of reclamation reefs in the South China Sea. To analyze the effect of coral mud on the stability of reef foundations formed by dredger fill, in this paper, the effects of initial concentrations, initial settlement heights, and salinity levels on the sedimentary characteristics of coral mud are discussed based on laboratory simulation tests. Comparative tests of marine sedimentary soil with similar particle compositions and of terrestrial silty clay with similar plastic indexes were carried out, and the sedimentation velocity characteristics of coral mud were identified at the microscopic level. The experimental results show that reducing initial concentrations and initial settlement heights are conducive to the coral mud filling process and that a medium salt content has no significant effect. The sedimentation rate of coral mud is roughly 3–7 times that of common soil, and the time spent in the isokinetic sedimentation stage is only 1/3 that of common soil. Microscopic studies show that the settling velocity of clay in water is proportional to the sphericity of flocs. According to our experimental results, the relationship between the sedimentation velocity and initial concentrations of coral mud is obtained and can be used to guide the design of similar calcareous soil projects across the globe and of dredger filling projects in particular.