Research On Differential Deformation Mechanism Of Graded Crushed Stone Buffer Subgrade In Seasonal Frozen Zone

At present,graded gravel is gradually tried as flexible base of pavement structure in China,but the buffer deformation capacity of graded gravel is not clear yet.In this paper,aiming at two typical diseases of graded gravel layer,frost heaving and uneven sedimentation,the basic physical and mechanical properties of graded gravel(particle size,friction coefficient,rolling friction coefficient,compaction degree,gradation,etc.)and their effects on angle of repose,California Bearing Ratio(CBR),graded gravel to buffer frost heaving and uneven sedimentation.According to the analysis of experimental and numerical calculation results,the relationship between the basic properties of the gravel particles and the angle of repose,CBR,and deformation buffer capacity is established.Finally,the angle of repose and CBR of the gravel are used to evaluate its ability to buffer deformation.Firstly,the static friction coefficient can be obtained by the angle of repose test of graded gravel,and the influence law of particle size,gradation,and degree of compaction on the static friction coefficient of graded gravel.Secondly,the EDEM three-dimensional discrete element calculation software is used to set the rolling friction coefficient of different crushed stone particles to simulate a series of angles of repose,and the appropriate rolling friction coefficient of gravel particles is determined after comparing with the angle of repose test results.Next,the numerical simulation of CBR for graded gravel is carried out in EDEM based on the particle contact behavior of the graded crushed rock in the penetration test,the numerical simulation of the CBR of the graded gravel from penetration tests,and theaccuracy of CBR simulation results is verified with the help of previous CBR test results.Then,simulation analysis of the friction coefficient,particle size,gradation,compaction and other factors on the impact of graded crushed stone CBR.Finally,combining the angle of repose and CBR test and numerical simulation research results,for the two kinds of diseases of graded crushed stone,frost heave and settlement,the spatial effect test of buffering differential deformation of graded crushed stone base was designed,the spatial effect measurement device was developed,and the crushed stone and The variables of the space deformation device are used to study the changes in the displacement disturbance area and resistance to deformation of the crushed stone surface when the disease occurs,and to study the influence of the test material parameters and molds on the cushioning deformation of the graded crushed stone.The analysis test and simulation results show that the angle of repose and CBR are proportional to the friction coefficient and the degree of compaction;the gradation design is reasonable,such as the frame embedding structure.The supporting capacity of the gravel skeleton is relatively strong.The actual measurement of the angle of repose and CBR And the simulation result will be larger;the angle of repose and CBR of the graded crushed stone are larger than other moisture contents under suitable moisture content.The deformation area at the bottom of the graded gravel base is large,and the graded gravel needs a larger buffer area and depth to buffer deformation;the sharper the bottom deformation of the graded gravel,the more obvious the effect of buffering frost heave deformation.Appropriate moisture content,compaction,and a dense and stable skeleton gradation can improve the buffering deformation capacity of the graded crushed stone.When the test result of the angle of repose of the graded crushed stone is large,the calculation result of CBR will be too large,and the gradation is broken.The rock realizes cushion deformation by "releasing" the degree of compaction or destroying the skeleton structure of the crushed stone;when the angle of repose test result is too small,the calculation result of CBR will not be ideal.At this time,the graded crushed stone mainly realizes cushioning through the "fluidity" Deformed.This research provides theoretical basis and practical guidance for the design of graded crushed stone base with strong cushioning deformation ability by studying the angle of repose,CBR and cushioning deformation capacity of graded crushed stone.