Creep Behavior And Equation Including Particle Breakage For Calcareous Sand

In order to investigate the creep behavior and equation of calcareous sands,a series of one-dimensional creep tests were carried out for calcareous dry sand samples with different three initial void ratios,the particle breaking degree of calcareous sand sample was measured by sieving test after the creep test,Hardin particle crushing potential,aspect ratio,roundness practical sphericity and fractal dimension are introduced as shape indexes Based on the experimental data,the creep rate and creep deformation curve of calcareous sand are analyzed in detail,and then the nonlinear creep constitutive equation of calcareous sand is constructed by combining the rheological element model.The results show that calcareous sands could exhibit significant nonlinear creep under axial stress,on the whole,the creep deformation process can be roughly divided into three stages: instantaneous creep,decay creep and stable creep.The main influencing factors of these three stages are particle rearrangement,particle slip and particle breakage.Moreover,the growth of axial strain is discontinuous,and it is mostly stepped up in a“stepped” form,which mostly occurs in the damping creep stage with a relative low stress level.In addition,as the creep time is the same,the axial strain increases with the increase of axial stress,but the increment gradually decreases.It can be preliminarily believed that the stress increment would not lead to a significant effect on the creep characteristics while the limited stress was encountered.Hence,it can be considered that under the combined action of axial stress and creep time,the creep characteristics of calcareous sand gradually increase nonlinearly.From the microscopic point of view,the obvious increase of particle breakage in the sample is the result of the increase of axial stress and creep time,which makes its nonlinear characteristics more significant.Based on the staged characterization of the creep deformation process of calcareous sand,considering the influence of initial void ratio and axial stress,the nonlinear creep model of calcareous sand is constructed by combining the rheological element theory model,and the prediction of the creep deformation characteristics of calcareous sand is realized by using the model.The prediction accuracy is high,and the equation is considered to be a good characterization of the creep deformation process of calcareous sand.