An Interpretation of the Stress-Dilatancy Turning Hook of Bioclastic Carbonate Sediments from the Perspective of Particle Breakage and Energy Dissipation Authors

Bioclastic carbonate sediments (BCS) are biogenic geomaterials widely distributed in tropical coastal regions and are distinguished by abundant irregular coral gravel (CG) particles and strong crushability. During shear, BCS commonly exhibit a characteristic downward-turning hook in the stress-dilatancy response, marked by a rapid reduction in dilatancy rate after the peak stress ratio is reached. The mechanisms linking this turning hook to particle breakage, energy dissipation, and CG composition remain insufficiently understood. This study investigates the shear behavior of BCS using both natural samples from burial depths and reconstituted specimens with varying CG contents. A quantitative framework is proposed to characterize the stress-dilatancy turning hook based on comprehensive experimental observations. Results demonstrate that particle breakage evolution can be consistently described by normalized plastic shear work that incorporates the initial void ratio. A new composite turning hook index Rt, is introduced to quantify the magnitude of the turning hook, and its relationships with plastic shear work, confining pressure, and CG content are established. Compared with traditional single-point descriptors, Rt more accurately captures the overall geometry and evolution of the turning path. These findings provide deeper insight into dilatancy mechanisms and support an energy-based interpretation of shear behavior in highly crushable soils.