Construction Of Large Triaxial Numerical Model Based On The Shape Of Rockfill Material

In recent years,the development of clean energy in China has changed rapidly,including water conservancy and hydropower projects that focus on hydropower development.In hydropower construction,earth-rock dams have the advantages of low investment,fast construction,and strong adaptability to the topography and geology of the dam site.They are one of the key development dam types.As the main building material of earth-rock dam,rockfill has the characteristics of good compaction performance,strong water permeability,large filling density,high shear strength,small settlement deformation and high bearing capacity.With the breakthrough of the earth-rock dam construction height from 200 m to 300 m,the material performance of the dam body is more and more fully exerted,and the safety margin of the dam body is gradually reduced.In order to solve this problem,it is necessary to carry out more in-depth research on the physical and mechanical properties of rockfill.Research methods mainly include indoor large triaxial tests and various numerical methods.However,the indoor test has a large workload and poor repeatability,and more importantly,the scale effect problem is difficult to solve.With the development of computer technology,the advantages of numerical simulation have gradually emerged.Among them,the discrete element method is more suitable for the numerical analysis of granular materials,and is widely used in the numerical analysis to explore the influence of different factors on the rockfill mechanics.Studies have shown that the shape of the rockfill particles not only affects the density and porosity of the aggregates,but also has an important effect on the mechanical properties of the material.The rockfill particles have large particle size spans,and particle shapes are irregular.Scholars used shape description indicators to describe irregular rockfill particles.In terms of numerical simulation,the construction method of the particle shape has gone through a process from simple to complex,two-dimensional to three-dimensional.In the early stage,a single disk or sphere was generally used,and later developed to use multiple disks,spheres or polygons.Next,the scholars proposed the raining method,the layered underpressure method,the geometric method and other methods to construct a series of irregularly shaped rockfill particles into particle aggregates,so as to carry out large three-axis numerical simulation to explore the shape of the particles against the heap influence of mechanical properties of rockfill materials.Therefore,how to generate rock-filled digital particles simulating the shape of particles and the large three-axis numerical model in a compacted state has become an urgent problem to be solved.The shape description index is used to describe the irregular rockfill particles,and the irregularly shaped rockfill particles are reconstructed by numerical simulation to further construct the particle aggregate.The construction method of the particle shape has gone through a process from simple to complex,two-dimensional to three-dimensional.In the early days,a single disk or sphere was generally used,and later it was developed to use multiple disks,spheres or polygons.Next,a series of irregularly shaped rockfill particles were constructed as a collection of particles using the raindrop method,stratified underpressure method,geometric method,etc.,and a large triaxial numerical simulation was carried out to explore the particle shape on the rockfill material mechanics Influence of characteristics.Therefore,how to generate rock-filled digital particles simulating the shape of particles and the large three-axis numerical model in a compacted state has become an urgent problem to be solved.In this paper,a single particle model of rockfill with irregular shape was generated based on the Fourier descriptor method,combined with the shape parameters of the rockfill,considering the modeling efficiency of the computer.The single particle model was optimized and reduced,and finally a large triaxial mesoscopic three-dimensional discrete element single particle model for numerical calculation of the model suitable for rockfill was established.The model construction used the rain-drop layered overpressure method to reconstruct a large triaxial numerical model with a particle size span of 2-60 mm and a porosity of 0.22.The numerical sample has a large particle size span and a small porosity.And the effect of particle shape,round particle,cubic particle,and rectangular particle on the mechanical properties of the rockfill was qualitatively analyzed.It is the basis of carrying out the numerical simulation of the full-scale large triaxial numerical shear test,and exploring the relationship between the particle shape description index and the mechanical parameters of the material.