PFC Simulation And Compaction Characteristics Analysis Of Asphalt Concrete Core Wall Rolling Process

The vibratory compaction method is usually adopted for asphalt concrete core wall construction.Compaction quality ultimately determines the wall’s stability and impermeability.The compaction quality of asphalt concrete core wall depends on the mix ratios of core wall asphalt concrete,grading and compaction parameters.As the on-site construction environment is changeable and complicated,the determination of reasonable compaction construction parameters under certain asphalt concrete mix ratios and gradations is very important for ensuring the compaction quality in an economical and efficient way.At present,the compaction parameters are usually determined according to engineering experiences or field tests.The former lacks theoretical basis,and the latter often consumes a lot of manpower and material resources.Therefore,this paper used the Particle Flow Code(PFC)of Discrete Element Method(DEM)to numerically simulate the vibratory compaction process of asphalt concrete core wall,which reveals the vibration compaction characteristics of the core wall asphalt concretes from the mesoscopic point of view,and studies the influence of different compaction parameters on the compaction quality of the asphalt concrete core wall.The main results are as follows:(1)A particle modeling method for the mix and gradation of core wall asphalt concretes was proposed.The contact model between different particles,e.g.coarse aggregate particles and asphalt mortar particles,was established,according to the physical and mechanical properties of the core wall asphalt concretes.Gravity sedimentation was carried out on the model to simulate the paving process and match the pre-construction state of the core wall asphalt concrete vibrating roller.Finally,a roller modeling and a crushing load application method based on compaction work per unit volume were proposed.(2)A PFC model of the core wall asphalt concrete static pressure test was established in this paper,and an inversion method for mesoscopic parameters of core wall asphalt concrete PFC model on the basis of support vector machine model(SVM)and adaptive difference algorithm(ADE)was proposed.Besides,the proposed method above was verified by multiple sets of chamber static pressure tests under different temperatures and different pressures.The results showed that: SVM model can fairly reflect the correspondence between input samples(parameters to be inverted)and output samples(simulated settlement).The simulated settlement amount with PFC using the mesoscopic parameters obtained from the inversion matched the physical test results well.The mesoscopic parameters gained from the inversion could provide conditions for the PFC simulation analysis of the subsequent vibrating compaction characteristics of the asphalt concrete.(3)A PFC model of asphalt concrete core walls was established,and the model was fit well with the cumulative settlement curve of the field test.The variation law of particle coordination number,velocity field and displacement field during PFC simulation of compaction process was analyzed,which disclosed the meso-compacting characteristics of core-wall asphalt concrete.Furthermore,the influence of different compaction parameters on the compaction quality of the core wall asphalt concrete and its sensitivity was explored,which provided a basis for reasonable determination of on-site construction compaction parameters.