Analysis On Deformation Characteristics For Roadbed Under Vehicle Loads

With the implementation of "One Belt One Road" and the proposition of eight economic areas,the economic of our country have developed rapidly,and Chinese economy has ranked second in the world.With the improving of people’s living standard,people long for a more developed system of traffic and logistics transportation.In this context,our country has put lots of manpower and material into the construction of infrastructure,such as roads and railways to meet people’s needs.With the development of traffic and logistics transportation,the number of vehicles on road have increased obviously.Furthermore,the heavy or overloaded traffic-induced road diseases are increasing year by year.In this thesis,the mechanical properties of roadbed under traffic were taken as the application background.Based on a new method used for the monitoring of roadbed deformation,characteristics of the roadbed’s dynamic deformation were recorded.Laboratory tests were conducted to obtain essential parameters of the roadbed,based on which a reliable numerical analysis model was built.The deformation responses of roadbed under complex conditions were investigated,the relationship between roadbed’s plastic deformation and the vehicle load was determined.An empirical formula for calculating the accumulative plastic deformation of roadbed with circulation times of vehicle load was established.The main work of this thesis are as follows.(1)Soil’s physical and mechanical properties of the roadbed were obtained through laboratory tests,which provided some indispensable input factors for the numerical simulation.Loading-unloading tests with a car(approximately 1.4 tons)were performed on the test road where FBG sensors had been installed to monitor the dynamic roadbed deformation.Monitoring results characterized the dynamic roadbed deformation and provided some references for the simulation.(2)For the purpose of understanding the vehicle-induced roadbed deformation,a road model has been established using the FLAC3 D software.Comparison ofsimulation results and monitored results indicated that the deformation characteristics obtained by simulation and in situ tests were consistent.Under the action of a 1.4tons car,the elastic deformation was about 8 times of that of the plastic deformation,i.e.,the deformation in roadbed was mainly elastic deformation and the plastic component took only a little part.Results presented here indicated that the road model,input factors and the computing method were reasonable.(3)When the numerical simulation can be verified by the in situ tests,the dynamic roadbed deformation under a single vehicle load and cyclic loads were calculated.The relationship between the plastic roadbed deformation and vehicle loads tended to be exponential.Combined with related studies,an empirical model was employed to describe the cumulative plastic deformation under cyclic loads.Numerical simulation was applied in combination with the laboratory tests and in situ monitoring to efficiently and reasonably analyze the dynamic roadbed responses under traffic,which will facilitate the research on road disaster prevention and mitigation or safety assessment.