Study On Asphalt Mixture Splitting Test Using Cohesive Zone Model And Three-Dimensional Discrete Element Method

The Indirect tensile test (IDT test) of asphalt mixtures is one of the contents in the processing of designing of asphalt mixtures and pavement structure, as well as an approach to study the damage mechanism of asphalt mixtures. Because of the simplicity of IDT operation and the similarity of the stress state between the middle part of specimen in the loading process and bottom pavement under load, the IDT test has been widely used in mechanical researches of asphalt mixtures.The discrete element method (DEM), one of the numerical simulation methods, is more applicable for simulating the micromechanical behaviors of particle assembly, which has significant advantages in simulating the non-continuum materials. Asphalt mixtures is a kind of typical non-continuum material, whose discontinuity mainly includes three parts, the discontinuity of material properties in the interface between aggregate and asphalt mastic, the discontinuity of adjacent aggregate particles and the discontinuity of adjacent air voids. By means of DEM, the microstructure model of asphalt mixtures is more intuitive, and the DEM has been widely applied in describing the meso-cracking propagation and the fracture processing of asphalt mixtures.The cohesive zone model (CZM) shows significant advantages in the study of crack propagation of asphalt mixtures, for example, the cohesive zone model can well simulate the whole process of crack propagation of asphalt mixtures and changes of mechanical properties during cracking, which contribute to the widely attention of application of CZM in the research of mechanical performance of asphalt mixtures.In this, paper, based on the laboratory IDT test, the force-displacement curves can be obtained with the help of a universal testing machine, and the CT scanning technology were combined with the digital image processing technology and 3D DEM, the selection of material parameters were based on the cohesive zone model, then the study of 3D discrete element simulation of asphalt mixtures started. In the modeling process of 3D IDT test of asphalt mixtures, the aggregates were generated on the basis of the real boundary coordinates while adopting the logic of ’cluster’, and the discrete elements were assigned by the contact-bond model.. Then the parameter effects on the simulation results were analyzed by means of 3D discrete element simulating which adopts loading rate, model parameters, temperature, or asphalt-aggregate ratio as the effecting index.The results of this paper show(reveal) that, based on the computed tomography(CT) and digital image processing technology, an IDT model of asphalt mixtures can be built intuitively using DEM;. With the cohesive zone model applying in the 3D discrete element numerical simulating for a splitting test of asphalt mixtures, the micromechanical properties of asphalt mixtures in the splitting process can be studied effectively. However, as a result of the large differences of the loading rate and loading form between numerical simulation and laboratory test, parameters of 3D discrete element model need adjusting to apply the CZM in the 3D discrete element modeling better.