Static and dynamic compressive performance of coral reef limestone: interpretations of rate effect from laboratory tests

Mechanical performance of coral reef limestone (CRL) is becoming an important topic in recent years due to the boom in offshore construction. However, as there is a lack of rock samples in specific regions, very limited progress has been made in terms of the compressive behaviour (both static and dynamic) of the CRL. Specially, proper descriptions and accurate quantifications of the strain-rate effect upon the compressive performance of the CRL remain to be performed, which will be the main emphasis of this paper. Four types of CRL, namely, coral framework (CF), coral boulder (CB), coral gravel (CG), and coral calcarenite (CC) limestone, were obtained from a human-made coral reef island in South China Sea. Static uniaxial and dynamic split Hopkinson pressure bar (SHPB) compression tests are conducted to obtain the strengths at very low and medium to high compressive strain rates, respectively. The strain-rate effect of the compressive strength is well described with the Herschel-Bulkley model, parameterising the static strength, the viscosity coefficient, the ‘shear-thinning’ index, and the reference strain rate. The overall quality of the CRL rock mass is then classified by the basic quality method, which is based on the uniaxial compressive strength and joint distributions of the rock mass. Variations of the Young’s modulus of the CRL rock mass under different strain rates are also discussed.