The Effect Of Different Factors On The Crack Propagation Cracking Of The Overlay

Overlay on old concrete pavement of asphalt layer to repair damaged, can not only effectively use the original pavement strength, extend the service life of pavement, and also can improve its performance, improve the driving comfort, is currently the most commonly used in practical engineering is the most economic repair methods. But as a result of reflection cracks in asphalt layer has the universality and severity, paving asphalt layer greatly shorten the service life and increase the cost of road maintenance, causing unnecessary economic losses.To reveal systematically the related factors influencing the reflection cracks and expansion, seeking to prevent reflection crack, the development of effective reference basis. In this paper, on the basis of previous studies, this paper introduces the domestic and foreign existing old cement concrete pavement asphalt layer reflection crack research methods, summarize the prevention and control measures, continue to influence the asphalt layer reflection crack propagation mechanism is analyzed. Based on fracture mechanics theory, think of the old cement concrete pavement crack and joint the defect of the original, will cause the stress concentration of the asphalt layer and internal injury, when the stress concentration and damage accumulation exceeds material and structure to resist damage threshold, add layer will produce reflection crack, thus causes the destruction of structure layer.Thesis mainly carried out the following research:1. According to fracture mechanics theory and finite element method(fem) to cause reflective crack of asphalt layer and extension mechanism are analyzed in series;2. To set up the finite element software ANSYS model and puts forward assumptions;3. Calculation analysis of vehicle load, temperature stress and both symmetric and asymmetric all factors under the influence of mutual coupling of asphalt layer bottom stress changes;4. Paving layer upon layer bottom stress changes, through the evaluation of asphalt layer modulus and foundation modulus, thickness of asphalt layer, initial crack width, cooling rate and other factors the influence degree of the change of reflection cracking, for practical engineering design and construction to provide theoretical reference to some extent.