| The expressway construction in southern area,going through the mountainous hills is inevitable,the coarse-grained soil are widely used in the high fill embankment,because its good engineering properties and advantages of convenience,but under the dual influence of long-term vehicle load and rainfall factors and coarse-grained soil fill embankment is more related to the settlement deformation of pavement diseases.In view of this,this paper is based on the National Natural Science Foundation of China:research on service performance evolution and state control technology of high coarse-grained soil embankment under dynamic wetting effect(51678073).The large indoor GDS dynamic triaxial tests in a series of cyclic load tests under different deviatoric stresses,moisture content and load frequencies was carried out,deformation characteristics in dynamic wetting were analyzed,and based on laboratory test results,the three-dimensional particle flow theory was introduced and used to simulate the dynamic triaxial test.The internal mechanism of coarse-grained soil filler deformation from macroscopic and mesoscopic perspectives were revealed.The main research achievements are as follows:(1)Based on the research results,the test plan of the coarse-grained soil filler permanent deformation was made,respectively under different moisture content and deviatoric stress and load frequency,the influence law of various factors and influence degree were analyzed,the results showed that the first stage of cyclic loading is less than 1000 times,plastic strain rapid increase to 80%of the total deformation,after more than 1000 times,the second stage for cyclic loading specimen show the dynamic response of elastic plastic strain was basically stable;Based on the cyclic loading test data,a model for estimating the permanent deformation of coarse grained soil was obtained.(2)Analysis of the specimen before and after loading by electron microscope scanning showed that the deviatoric stress and moisture content have great influence on the macroscopic deformation and microstructural changes.As the deviatoric stress increases,the degree of homogeneity of the internal structure pores and the probability entropy are reduced,the order of pores is increased,and the average shape factor is increased.As the moisture content of the sample is increased,the probability entropy is decreased.The order is improved,the pore shape is elongated,and the complexity is increased;there is no obvious regularity in the internal structure of the sample as the load frequency increases.(3)Based on particle flow theory and laboratory test results,the yield stress as the medium,the curve of particle bond strength changing with moisture content is obtained;PFC3D is used to establish discrete element calculation model of dynamic triaxial test,The curve of permanent deformation with loading times is obtained,through the intuitive graphical output can see the change of contact force between particles,velocity,displacement and coordination number,quantitative interpretation under the action of different factors affecting the mechanical response of the mesoscopic mechanism,and and verify the consistency between the numerical model and laboratory tests.(4)By analyzing the variation trend of porosity,coordination number,force chain,the displacement of particle of test specimens in numerical simulation,the microscopic evolution law of deformation of specimens under the action of load was revealed.The results show that the porosity decreases rapidly and the particles move and roll violently before loading 1000 times,resulting in uneven distribution of force chain.After loading for 1000 times,the porosity reduction tends to be flat,the coordination value tends to be fixed,the number of contact between particles is large,the forces on the particles can cancel each other and balance each other,and the distribution of force chains is uniform.Its internal evolution law conforms to the deformation characteristics during cyclic loading. |
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