Effects of size and loading rate on the mechanical properties of single coral particles

A series of single particle crushing tests were conducted on 400 coral particles with size ranges of 3-5 mm, 6.5-8.5 mm and 10-12 mm at loading rates of 0.1-50 mm/min. The effects of size and loading rate on the mechanical properties are assessed in terms of the frequency distribution of crushing strength, fragmentation mode, fractal dimension, and fracture energy density. It is proved that the crushing strength frequency distribution perfectly follows the Weibull statistics law, decreasing with an exponent of -0.286. A satisfying rate dependent equation is proposed to account for the characteristic tensile strength enhancement regarding strain rate. The fragmentation behaviour in conjunction with monitored load-displacement curves were classified into four typical modes. As the size decreases, the fragmentation mode changes from asperities breaking and surface grinding to primary brittle splitting. A higher applied loading rate may lead to an increasing possibility of major splitting occurrence. The fractal dimension is 2356 for coral particles, which is a bit larger than that of quartz sands and was found to be proportional to the natural logarithm of the strain rate. The fracture energy density tends to decrease as the particle size increases while to increase with increasing stain rates. (C) 2018 Elsevier B.V. All rights reserved.