A Study of Load Responses towards the Pavement Edge

A major part of the national and county road network in Norway consists of two-lane roads with relatively narrow shoulders. The width of the roadway is limited, forcing heavy trucks to drive close to the pavement edge. This represents a considerable deteriorating effect on these pavements, which typically consist of granular base materials and thin asphalt surfacing. The result is often premature cracking and deformations along the pavement edge. Despite the fact that pavement edge damages represent a great problem for the Norwegian road network, little research has been performed on this topic. This is the main background for the present thesis work to focus on pavement edge damages and load responses towards the pavement edge. Chapter 2 gives a brief presentation of the basic theory of continuum mechanics together with some elastic constitutive material models. The general elasto-plastic theory is also described. Further, methods and programs based on elastic layer theory developed for structural analysis of pavements are presented. Finally, advantages and basic principles for the finite element method are discussed. In Chapter 3 the different types of pavement edge damages are described. Further, the factors influencing the strength of the pavement edge and damage development are discussed. To get information of the variation of bearing capacity over the cross section of existing roads, own FWD measurements are performed at different sites in Sør-Trøndelag county. As expected, a considerable decrease in bearing capacity towards the pavement edge was found. Also a minor field study on the effect of varying side slope is accomplished. The structural effect of gradually steepening the side slope is measured by FWD and plate loading tests. Chapter 3 also contains the findings from a literature review on measurement and calculation of pavement edge effects. Only a small number of articles on these subjects were found. A full-scale pavement test has been performed at Sandmoen near Trondheim. Two pavements with different subbase materials were constructed, one of them instrumented for the measurement of stresses and strains in the base and subbase layers at different offsets from the pavement edge. The construction work, materials, sensor types and positions are thoroughly described in Chapter 4. Results from Sandmoen test field are presented in Chapter 5. Responses to three different types of loading have been measured. These are controlled wheel loading, FWD