Study On Gradation Segregation Of Hot Mixture Asphalt Caused By Screw Conveyor Based On Discrete Element Method

Asphalt pavement is widely paved with the advantages such as low running noise,no seams, flatness and simple maintenance. However, particles of Hot Asphaltmixture may isolate and aggregate according to their sizes in Asphalt pavementconstruction, which is gradation segregation. Gradation segregation caused by screwconveyor, more prominent and difficult to control, seriously influences the pavementquality. It is more difficult to further analyses gradation segregation caused by screwconveyor because of the complicated effect of screw conveyor parameters ongradation segregation, difficult control of experimental factors in paving test, thetedious process of data measurement and small amount of measurement information,Thus, In order to design more reasonable screw conveyor parameters and reducegradation segregation caused by screw conveyor, this paper studies gradationsegregation of Hot Mixture Asphalt based on discrete element method.The major work of this paper is as follows:(1) Summarize the research status of gradation segregation caused by screw conveyor,including asphalt mixture simulation, Gradation Segregation and screw conveyor.(2) Establish discrete element model of screw conveyor. Based on the characteristicsof asphalt mixture and screw conveyor, establish gradated discrete element modelof screw conveyor and geometry model of screw conveyors on the basis of periodspace respectively. The influence trend of fill level on gradation segregation is in agood agreement with the practical experience and verifies the feasibility of themodel of screw conveyor.(3) Reduce the calculated amount of discrete element model of screw conveyor. Bycomparing the discrete element simulation results under different mixing time,select a reasonable computation time; accelerate the simulation speed significantlythrough reducing the number of particles on the basis of the decrease of volume ofthe period space.(4) Optimize the structure and parameters of screw conveyor and reduce dramaticallythe degree of gradation segregation. Ensure the simulation scheme based on theDesign of Experiment and get the response. Establish the response approximationmodel of gradation segregation caused by screw conveyor based on Response SurfaceMethodandoptimizethescrewconveyorparametersbasedonGeneticAlgorithm.(5)Analyzethereasonsofgradationsegregationcausedbyscrewconveyorbythestudyingthedistributions,sizeandorientationofparticlesvelocity.