Numerical And Experimental Studies Of Crack Expanding In Asphalt Pavements

The asphalt pavements with short construction period,comfortable driving experience,is the main advanced level road surface form. At present,the advanced level road mainly chose two patterns,they are half stiffness asphalt pavements and cement concrete pavements surface adding asphalt pavements. The cracking problems of asphalt pavements is met by nearly all the countries in the world,and main damaged form of it includes:the fatigue cracking,the trcak cracking,and the thermal cracking. Research on initiation mechanism and propagation behavior of cracks in asphalt pavements is necessary for a sound evaluation of mechanistic behavior of pavements. It is a great help to us to understand the state of the stress field and crack expanding path,to improve understanding of the mechanism of pavement damage and premature failure,and to provide guidance for pavement engineers in designing and maintaining asphalt pavements. It also has especially important significance to boosting highway traffic infrastructural facilities health development of our country.Under the condition considering thermal and traffic loads of the asphalt pavements,the computing method of stress intensity factor in problem of fracture mechanics has been discussed. And formation of the two singularity elements,six knot triangles element and eight knot quadrilaterals element has been proved. Singularity field of the crack tip,the fracture criterion of mixed-mode crack and the length of the expanding crack has been also discussed.According to fracture mechanics principle,two-dimensional ANSYS finite element method procedure,simulation of the crack expanding route under the condition of thermal load and traffic load has been written . Fatigue test at the asphalt beam under Instron 1341 material test system was finished. Comparison the crack route on the asphalt beam and two-dimensional ANSYS finite element method procedure, the result has been fully matched. It can be concluded that I type loading (tension load) is that main expanding impetus of crack,II type loading (shearing load) makes a crack deflexion happened and affects the initial angle of crack.Combining of fracture mechanics and finite element method has provided effective way for resolving the crack expanding problem of the asphalt pavements. The writing of two-dimensional ANSYS finite element method procedure and the study of expanding routes fatigue test has important theory and actual project value to the destroying of the asphalt pavements,early phase damage of the structure and knowing and understanding the asphalt pavements.