Study On The Effect Of The Particle Morphology On Sand Crushing Behaviors Based On The XFEM

A large number of geotechnical projects involve the particle crushing phenomenon in geomaterials,such as dam foundation,pile foundation and railway bed.Previous studies have shown that the behavior of particle crushing has a significant effect on the constitutive behavior of geomaterials in high stress state,such as compression,shear strength,dilatancy effect and critical state behaviors.However,the micro mechanisms of the particle crushing behavior of geomaterials is still a hot topic and difficult problem need to be solved.With the development of high resolution X-ray CT scanning and advanced numerical simulation technology,the effect of particle morphology on particle crushing behaviors has been more and more interested to the geotechnical researchers.Therefore,this thesis chosen an offshore quartz sand(LBS)as the research object,and systematically studied the effect of the particle morphology on crushing behaviors of sand particles.Firstly,thirty typical LBS particles randomly selected subjected to the high precision X-ray CT scanning.The morphological information of each individual sand particle were obtained by using a series of image processing techniques.A continuous surface mesh of each individual sand particle can be reconstructed by the spherical harmonic(SH)function.Based on the SH-reconstructed surface mesh,practical approaches were proposed to calculate the morphological parameters of sand particles including volume,surface area,aspect ratio,roundness,sphericity and convexity.The statistical results show that the surface area of sand has a positive correlation with the volume,while sphericity,convexity,roundness and aspect ratio decrease with the increase of particle volume.Roundness and aspect ratio are the most sensitive to the morphological changes of the sand particle.Based on the SH-reconstructed surface mesh,the finite element model of the realistic sand particle was established in ABAQUS.Furthermore,the development of the crack was simulated by the extended finite element module in ABAQUS.The efficiency of the method was firstly validated by the simulation of the Brazilian splitting test.The effect of particle morphology on the crushing strength,crushing mode and crack propagation was investigated by a series of numerical single particle crushing tests.The numerical results showed that the process of the uniaxial compression of a single particle can be divided into five stages including contact rolling,elastic compression,crack initiation,crack penetration and brittle fracture.Finally,the Weibull distributions of the crushing strengths of thirty sand particles and their corresponding equivalent spherical particles was analyzed.Moreover,the correlation between the crushing strengths and the morphological parameters of the sand particles was discussed.The statistical results showed that the characteristic crushing strength and Weibull modulus of the equivalent spherical particles are larger than those of the sand particles,which indicates that the particle morphological features weaken the crushing strengths of the sand particles,while increase the variation of the crushing strengths.The correlation showed that the crushing strength of sand particle was most sensitive to its roundness and aspect ratio.The findings of this thesis reveals the micro mechnisms of the effect of the particle morphology on particle crushing behaviors of granular sands,which can provide significant theoretical foundation for the establishment of the constitutive model and the engineering applications of crushable sands.