Mechanical properties of coral reef sediments containing non-plastic carbonate fines

Abstract

Coral reef sediments contain not only coral sandy-gravel, but also carbonate bioclastic fines originating from biogenic skeletons. In this paper, one-dimensional consolidation and triaxial compression tests were performed by using coral reef sediments containing different contents of non-plastic fines to evaluate the influence of fine content on mechanical properties. According to the consolidation tests, the compression index C c ranged between 0.07 and 0.13. The coefficient of consolidation c v was found to be a value of the order of 10 3 cm 2 /d for coral reef sediments containing more than 60% carbonate fines displaying primary consolidation. The shear behavior of fines was similar in dilatancy property to the sandy gravel, because the fines consisted of silt-and clay-sized non-plastic carbonate particles. The angle of shear resistance φ´ in consolidated undrained shear is similar to that of φ d in drained shear. Both parameters decreased with increased fines content. The undrained shear strength c u was determined by the maximum value of the effective stress ratio (q/p´) in the stress-strain relation. The shear strength ratio was found to be c u /p=0.32 for non-plastic carbonate fines.