Study On Mechanical Properties And Macro-micro Failure Mechanisms Of Crushed Stone Aggregate Under Cyclic Loading

As a filling material for bulk structure engineering,gravel aggregate is widely used in dam engineering,highway roadbed,railway ballasted track structure and other projects.Its mechanical properties directly affect the safety and stability of the engineering structure.In this paper,the mechanical behavior and influencing factors of gravel aggregate under cyclic loading are studied comprehensively by means of experimental analysis and numerical simulation.The relationship between mechanical parameters and influencing factors of gravel aggregate is explored.Fracture mechanism of gravel aggregate is analyzed from macro and micro perspectives,and a method to improve the mechanical properties of gravel aggregate is proposed.The main research results are as follows:?1?The effects of particle size distribution,material ratio,loading frequency and amplitude on macro-mechanical properties of gravel aggregate are analyzed through cyclic loading test of gravel aggregate.It is found that adjusting the content of fine particles,gradation curvature coefficient or rock material can effectively improve the mechanical properties of gravel aggregate.In addition,the deformation characteristics of gravel aggregate increase with the increase of load frequency or amplitude.Fragmentation is positively correlated with load amplitude and negatively correlated with frequency.?2?The macro and micro mechanical properties of gravel aggregate under experimental conditions were simulated and analyzed by PFC^2D particle flow software,and the results are compared with the experimental results.It is found that the macroscopic mechanical properties of gravel aggregate are basically consistent with the experimental results,the meso-parameters which accord with the macro-mechanical properties of gravel are obtained.By constructing fragile particle clusters,the fracturing evolution law of gravel aggregate under different influencing factors is analyzed from macro and micro perspectives.?3?The simulation analysis of gravel aggregate under high frequency condition is carried out,evolution law of macro and micro mechanical properties of gravel aggregate under high frequency condition is obtained,and the fracture mechanism is revealed.It is found that there is a linear relationship between deformation parameters and frequencies at high frequencies,but there is an exponential relationship with the amplitude.As a turning point of high and low frequencies,the evolution of mechanical properties of 10Hz is not within the normal range,and there are different trends with other frequencies.?4?The study found that under the condition of low gradation curvature coefficient,excellent crushing resistance of crushed stone or low load frequency and amplitude,the settlement deformation of gravel aggregates is small.In addition,the size of the fine particles in the grading also has a certain influence on the crushing resistance of the aggregates.