Dynamic constitutive model of coral sand under blast loading

Abstract

Coral sand is widely distributed in the large area of reefs and lagoons in the South China Sea. During the construction of various projects on islands and reefs, the coral sand is extensively used as a local material resource. It is very important to determine the threshold of the reef engineering to resist extreme impact loads when the islands and reefs covered with coral sand was suffered from dynamic disasters such as penetration and explosion. The coral sand dynamic constitutive model is a key component for protection engineering design when engineering calculations are required. Based on the results of SHPB experiment and static compression experiment of coral sand from the previous works, a method was proposed to determine the equation of state of coral sand based on the law of strain rate strengthening effect by comparing the static compression curves and the dynamic compression curves. It has been proved that the average pressure of the compression curve can reach more than 100 MPa by using this fitting method.The parameters of the dynamic constitutive model of coral sand were determined through the processing of a lot of experiment results. Based on the hydrodynamic elasto-plastic model and the Perzyna viscoplastic cap model, combined with the LS-DYNA finite element program, the applicability of the dynamic constitutive models was verified by contrasting the numerical calculations and experimental results of the coral sand suffered from the projectile penetration and the blasting of explosive. According to the established model, numerical calculations of penetration and explosion in coral sand with different compactness levels were carried out using the hydrodynamic elasto-plastic model. The results show that the compactness levels of coral sand have a greater influence on the attenuation of the blasting wave and less on the penetration depth. This is because the poorly graded original coral sand has a smaller measurement difference between the maximum and minimum dry densities.