The role of glauconite content in controlling sand crushing and compressibility

Shijin Li , Hannes Claes, Hadrien Rattez

Glauconite-rich sands are increasingly posing engineering challenges in offshore and nearshore developments, since their mechanical behaviour remains poorly understood owing to the extreme crushability of glauconite grains. Particle crushing in these sediments alters stiffness, compressibility, grading, particle morphology and, consequently, engineering performance. This study presents a comprehensive experimental programme to quantify the crushability of two types of pure glauconite, glauconite-silica mixtures, and silica sand under one-dimensional oedometric compression. Loading-unloading oedometer tests arrested at different axial strains were conducted on five materials containing varying glauconite, in both dry and saturated conditions. High-resolution laser diffraction and dynamic image analysis were used to characterise the evolutions of particle size and shape. The results show that glauconite exhibits substantially lower yield stress and requires far less work input to initiate crushing than silica sand. Yielding stress and threshold work decrease nonlinearly with increasing glauconite content, while relative breakage grows approximately linearly with strain. All materials evolve toward finer, fractal particle size distributions, and a robust exponential relationship between relative breakage and fractal dimension is established. Shape analysis reveals progressive elongation and edge irregularity with breakage, with glauconite retaining more equant geometries compared with silica. By integrating stress-strain behaviour, energy dissipation, grading evolution, and particle-shape change, this work presents a unified experimental framework for understanding crushing of glauconitic sands. The results support improved foundation design, breakage-aware constitutive modelling, and assessments of construction (e.g., pile installation) and long-term performance in glauconite-rich deposits.