Research On The Particle Breakage Mechanical Characterictics And Constitutive Model Of Calcareous Sand Under Triaxial Conditions

Calcareous sand is a special marine geotechnical medium, which has unexpected physical and mechanical property due to its origin and fabric. It is demonstrated that the particle crushing is a main factor affecting the property of calcareous sand. Currently, the study on the mechanical behavior of calcareous sand has made great achievement, while the research on the constitutive model for calcareous sand incorporating particle breakage is not so much. In this study, serials of shear laboratory tests were carried out and the shear mechanical behavior of calcareous sand was presented thoroughly. Many parameters influencing particle breakage and the mechanics of grain rupture were analyzed. The constitutive model for calcareous sand incorporating particle degradation was developed and the verification of the model was also presented. The main work can be concluded as follows.1,Axisymmetric specimens of calcareous sand were tested in drained and un drained triaxial compression tests between confining pressures of 0.1 and 3.2MPa. The triaxial shear mechanical behavior of calcareous sand was presented.2,Based on the overview of the different modes of grain breakage and different definitions of existing particle breakage factors, many parameters influencing grain breakage were analyzed, such as mineral component, grain size, grain composition, stress level, and shear strain. The characteristic particle stress acting on a particle in a sample was calculated by a simple formulation.3,The grain rupture mechanics of calcareous sand was analyzed. A relationship between the energy consumption due to particle breakage, angle of friction, dilatancy, and deviator stress ratio was derived. It may be helpful to distinguish the effect of particle breakage, dilatancy, and the basic friction component of shear strength for calcareous sand and other cohesionless soils.4,In the current model, a plastic flow rule has been developed incorporating the energy consumption due to grain crushing during shear deformation. A non-associated flow and a kinematic type yield locus have been adopted in the model. The effects of grain breakage on the plastic distortional and volumetric deformations are incorporated in the current model. The stress-strain formulations are developed within the general critical state framework. The model can accurately predict the stress-strain and volume change behavior of coarse granular aggregates. The plastic dilation and contraction features of coarse aggregates at various confining pressures are well captured, and the strain-hardening and post-peak strain-softening behavior of calcareous sand adequately represented. A particular feature of the model is its capability to predict the degree of particle breakage at any stage of shear deformation.