Analysis Of Asphalt Pavement Respones Under Multiole Wheel Load Based On Material Nonlinearity

In order meet the transport needs of largelogistics as well as solving the contradiction between transport economy and over-loading, multi-axis heavy trucks become more and more popular. At the same time, the effects of multi-axis heavy vehicles have new requirements for road structure and pavement materials.For example, the nonlinear properties of pavement materials under heavy load cannot be ignored in pavement design, especially with the increase in flexible pavement in recent years. So through vehicles investigation, materials research and numerical simulation, thearticleanalyzes the impact of sub-base and subgrade geomaterial nonlinear properties on pavement structural responses.Then, based nonlinear finite element model, the effects of multi-axis loading on pavement structural responses are also analyzed.In the article, the current situationdevelopment trendof trucks in Chinais investigated firstly. The result shows that China’s heavy-duty trucks experienced rapid growth in the past decade. Besides, multi-axis heavy vehicles accountfor about 50% of the total number of trucksin urban expressways and provincial roads in China. With the development of large logistics, multi-axle heavy duty vehicles will be the trend of China’s future trucks. In order to systematically analyze pavement responses under multi-axis heavy loadas well as consideringnonlinear material properties, the paper studies the following aspects.Nonlinear stress-dependent models are employed in base and subgrade layers to properly characterize pavement geomaterial behavior. A systematic study on stress-dependent model is conducted to reflect the nonlinear property. By fitting the resilient modulus test data of graded gravel, ARA model parameters of three different graded gravelsare obtained. As forearth-based materials, based on theinvestigation andassessmentof the flexible pavement conducted bythe Federal Highway Administration in Illinois, four differentsoil base types from strong to weak are analyzed. Then, the bilinear stress-dependent model parameters of the four soil base types are selected to do calculation in next step.Then, in order to achieve Numerical analysis of nonlinear materials in ABAQUS, UMAT subroutine is used in finite element analysis. Based on the finite element theory, the constitutive material models of gravel base and subgrade are programed respectively by using tangent stiffness algorithm.Following that, a finite element model (FEM) of typicalpavement is built to analyze pavement responses under multi-axis heavy-duty load considering pavement material nonlinearity.The results are then described in terms of the effects of base nonlinearity, subgrade nonlinearityand the two layer materials on four criticalpavement responses, namely longitudinal stress, surface deflection, tensile stressfor bottom of layers, and subgrade strain. The results show that the nonlinear characteristics of macadam sub-basecan enhance pavement structurecompared to the elastic scenarios.However, when the nonlinearcharacteristics of the two layer materials are considered, the indicators of pavement responses are the most unfavorable conditions.With the increase of load, each road nonlinear response indicators show growth, especially for subgrade strain, indicating that overloaded has great impacts on road performance.In the end, based on the nonlinearcharacteristics of subgrade and subgrade materials, pavement responses under uniaxial, biaxial and tri-axial loads are compared. Meanwhile three types of base materials and four types of subgrade soils are also analyzed to investigate the effects of geomaterial properties.The results indicate thatmulti-axis loads lead to moresurface deflection and subgrade strain than uniaxial load.However,a lower tensile stressfor bottom of layersis found under multi-axial loading.Therefore, multi-axial loads could have significant impact on pavement rutting and have little impact on pavement fatigue.