Experimental investigation on mechanical behavior and particle crushing of calcareous sand retrieved from South China Sea

Calcareous sand containing weak particles originated from the deposition of skeletal residue of marine organisms is susceptible to significant particle crushing under compression and shearing. The breakage of grains results in excessive deformation and foundation failure. This study focuses on the mechanical properties and particle crushing of calcareous sand retrieved from Nansha Island, South China Sea. A series of isotropically drained and undrained triaxial compression tests were performed on reconstituted calcareous sand samples at different initial densities and at a wide range of confining stresses. The amount of particle crushing for calcareous sand after shearing was measured and quantified. Experimental results demonstrate that the shear response of calcareous sand had been well interpreted within the critical state framework. The amount of particle crushing for calcareous sand increases with increasing density and confining stress. Compared with the undrained condition, a larger amount of particle crushing of calcareous sands is observed in the drained triaxial compression test. Stress-dilatancy curves exhibit similar varying tendency for calcareous sand. Multiple critical state lines for calcareous sands with different initial densities are identified in the void ratio and logarithm of the mean stress plane. Considering the variation in stress ratio at the critical state induced by particle crushing, all stress paths are normalized to determine the state bounding surface for calcareous sand at varying densities and stresses. •Particle crushing for calcareous sand is jointly governed by density, stress level, and drainage condition.•Particle crushing-induced position shift of critical state line is observed for calcareous sand.•Bounding state surface is identified for calcareous sand at various initial densities.