Development And Application Of Viscoelastic Damage Model Of Asphalt Concrete Based On Particle Flow

Asphalt concrete is widely used in the face and core walls of earth rock dams because of its good seepage resistance,strong deformation ability and seismic performance.At present,there are more than 100 asphalt seepage dams in China,most of which are in the western region with high seismic intensity and frequency.The dynamic characteristics of asphalt concrete are worth studying;In addition,asphalt concrete is a kind of discrete material composed of asphalt,aggregate and fine aggregate.The existing analysis methods are mostly based on the theory of continuum mechanics,which is difficult to reflect the meso mechanical behavior.Therefore,based on viscoelastic theory and damage evolution theory,this paper establishes viscoelastic damage model,uses C++language to write dynamic chain library file,and develops viscoelastic damage contact model on PFC3D platform.The single connection key is used to verify the correctness of the viscoelastic damage contact model,and the sensitivity analysis of parameters is carried out to provide guidance for the subsequent application.The three-dimensional random aggregate model was established by PFC3D,and the viscoelastic behavior between asphalt matrix,asphalt matrix and aggregate was simulated by viscoelastic damage contact model.The crack quantity law of asphalt concrete under the condition of temperature range of-20 ℃～10℃ and strain rate of 10^-5s^-1～10^-2s^-1 is studied.Based on this,the damage evolution law is analyzed,the law of macro and micro energy evolution is discussed,and the failure mechanism of asphalt concrete is explained from the energy angle.The main research results are as follows:（1）The viscoelastic constitutive model is constructed by parallel connection of spring and Maxwell body,and the secondary development of viscoelastic damage model is realized in PFC3D.The correctness of the program is verified by the single connection key model.The influence of meso parameters on meso contact behavior in contact model is studied,and the qualitative relationship between macro mechanical parameters and meso parameters is obtained.（2）The above model is applied to the numerical simulation of uniaxial compression test of asphalt concrete.The deviation of macro mechanical parameters obtained by numerical test and indoor test is within 15%.The stress-strain curve is in good agreement with the development law of failure form.It shows that the viscoelastic damage model can simulate the viscoelasticity of asphalt matrix better.（3）Based on the numerical calculation,the development law of the fine crack of asphalt concrete is studied.The germination,aggregation and penetration of micro cracks lead to the appearance and development of macro cracks,which eventually leads to instability and failure of the specimen.The development of micro cracks is greatly affected by temperature and strain rate.The number of micro cracks increases with the increase of strain rate,and the occurrence time nodes advance and the development rate is accelerated;With the decrease of temperature,the development rate of micro fracture is accelerated and the number of fractures increases.In the whole failure process,with the increase of strain,the damage increases slowly to the last region.（4）The macro meso energy evolution of asphalt concrete under different temperature and strain rate is studied.When the same strain is reached,the macro elastic energy and the macro dissipation energy increase with the decrease of temperature（or the strain rate）,the rate of accumulation and release of elastic energy and the dissipation rate of dissipative energy increase with the decrease of temperature（or the increase of strain rate）.While the micro dissipative energy increases with the increase of strain rate under the same strain level.