Numerical Simulation Of Particle Breakage Of Rockfill Under True Triaxial Stress

Rockfill material is rich in reserves and can be found in a number of places,and is widely utilized in all kinds of geotechnical engineering construction because of its numerous excellent engineering properties.The special mining method resulted in internal defects and sharp angles.Its particles are largely point-contact or point surface-contact,and they are prone to angular fracture under external force,resulting in volume contraction of rockfill material and lowering shear strength.Particle breakage is one of the key elements impacting rockfill mechanical properties,according to researchers at home and abroad who validated this through laboratory tests and numerical simulation models.Currently,most research on the rockfill particle breakage characteristics uses the traditional triaxial test,which does not accurately and comprehensively reflect their mechanical properties,while the laboratory true triaxial test on rockfill material is limited by the development of test equipment and key test methods.The discrete element method has the natural advantage in investigating the granular materials,and after decades of research,it can precisely and efficiently simulate such problems as particle breakage.In this paper,a true triaxial numerical model of rockfill material is established using PFC^3D particle flow software,and true triaxial numerical experiments of non-breakable and breakable rockfill particles are conducted to explore the particle breakage and evolutionary process,as well as the influence of particle breakage on soil strength and deformation characteristics.The main conclusions are as follows:（1）Developing the program of true triaxial numerical test for non-breakable and breakable rockfill particles,and sensitivity analysis of the microscopic parameters included in the model was performed to have a further understanding of the influence of each microscopic parameter on the macroscopic mechanical properties.The reasonableness of the selected microscopic parameters and the correctness of the program algorithm was validated using accessible laboratory rockfill material test results.（2）Performing the true triaxial numerical tests on non-breakable and breakable rockfill particles at different confining pressure and intermediate principal stress,the influence of confining pressure and intermediate principal stress on the strength and deformation of the two samples were summarized from a macroscopic perspective,and the variation of force chain was examined from a microscopic perspective.Simultaneously,a program was designed to quantitatively monitor particle breakage during the loading of breakable rockfill particles in real-time.（3）Comparing the results of the true triaxial numerical tests on non-breakable and breakable rockfill material,the influence of confining pressure and intermediate principal stress on breakable particles were investigated,and it was discovered that the particle breakage evolution process can be generally divided into three stages.The influence of particle breakage on the strength and deformation characteristics was quantitatively evaluated,and a corresponding mathematical description was provided.