Creep and particle breakage in coral sand and development of a modified burgers model

This study investigates the high-pressure one-dimensional creep and progressive particle breakage of coral sand from the South China Sea. A series of high-pressure oedometer tests were performed under varying vertical stresses (1 ∼ 4 MPa), loading durations (up to 10,000 min), and median particle sizes ( d 50 = 0.8, 1.3, and 2.5 mm). The results indicate that creep deformation is highly time-dependent and size-sensitive, exhibiting a distinct three-stage progression. Particle breakage, quantified by Hardin’s index ( B r ), is highly progressive and follows a sigmoidal growth pattern with stress. Crucially, B r uniquely correlates with vertical strain and scales linearly with total input work, confirming the independence of grading. To capture these non-linear behaviors, a modified Burgers soft-matter model was developed by incorporating a fractional soft-matter element and a stress-size coupled formulation for pre-creep strain. The proposed model yields excellent predictions of the temporal creep curves, providing an empirical framework for representing the one-dimensional creep response of coral sand.