Research on the penetration characteristics of coral sand based on a visco-hypoplastic constitutive model

This study investigates the penetration characteristics of coral sand based on hypoplasticity theory. The Gudehus-Bauer (GB) hypoplastic constitutive model was optimized by modifying the particle hardness parameter to incorporate strain rate effects, leading to the development of a visco-hypoplastic constitutive model for coral sand. Penetration experiments were conducted under different strain rates, penetration velocities, and compaction levels, and the erosion morphology of projectiles during high-speed penetration was analyzed. Additionally, numerical simulations of projectile penetration were performed using the Smoothed Particle Hydrodynamics (SPH) method to explore the deceleration and deflection behavior of projectiles during penetration into coral sand. It is found that the particle breakage in coral sand is identified as a key factor causing significant deflection of the projectile, and the cavity diameter reaches the maximum at the turning point of the penetration depth curve. The coral sand offers less resistance to penetration than that of silica sand. Furthermore, the visco-hypoplastic model for coral sand, which incorporates strain rate effects, was calibrated against the quasi-one-dimensional SHPB impact compression experiment results from previous studies, demonstrating that the model can describe the response of sandy soils under different strain rates using a single set of parameters.