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Title: Investigating the causes of surface cracking in flexible pavements using improved mathematical models
Author: Merrill, D. B.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2000
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In the past, surface cracking in flexible pavements was thought to be caused by fatigue of the lower layers. Consequently, cracks in the surface were assumed to be full depth and indicative of a major structural problem. Recent investigations suggest that this is unlikely to be the case and that cracks appear to begin at the surface and propagate downwards. No conclusive explanation exists for the mechanism behind the formation of these surface cracks. This work aims to improve the understanding of the phenomenon using mathematical modelling. It was demonstrated that the limitations associated with existing models make them unsuitable for the study surface cracking. Moreover, it was apparent that the response of the surface was dominated by the tyre contact stress distribution. A 3D finite element pavement model was produced with the ability to define the tyre loading conditions in a more realistic manner. It was found, when using measured tyre contact stresses, that tension in the surface can be produced. The model was later adapted to enable a crack to be inserted into the surface and the likely propagation of this crack was explored using fracture mechanics. It was discovered that surface cracks were unlikely to be propagated by tyre stresses alone. After this discovery, a 2D finite element thermal cracking model was analysed using fracture mechanics including realistic temperature gradients. The stress intensity at the crack tip was shown to reduce dramatically with depth, indicating that crack growth speed will be reducing or even stopping entirely. This process concurs with the observed behaviour of surface cracks. It was concluded that although tyre stresses may influence the appearance of surface cracking, such as in the case of longitudinal cracks, the effect of temperature and ageing is more significant.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available