AbstractThis thesis focuses on a laboratory investigation of the tyre/grooved runway surface interface. A critical review of available literature identified significant knowledge gaps. Most literature relates to the tyre/road surface interface with relatively little considering grooved runway asphalt. There is little literature related to laboratory-based investigation identifying the need for new laboratory methods.
For example, no method is specified to assess the wear characteristics of grooved Marshall Asphalt (GMA) to predict its in-service performance. Performance is based on the initial skid resistance value and does consider the evolution of skid resistance and other interface characteristics during the runways life span. A new test method was developed using the Road Test Machine to subject asphalt test specimens to low-speed, high-stress conditions to simulate wear, enabling the performance of the GMA to be assessed. It was found that grooving contributes positively to skid resistance; however, there is a balance between optimum skid resistance and asphalt degradation as all dimensions considered wore differently depending on rib width/groove spacing ratio.
Photogrammetry generated a total of 88 3D models of the test surfaces. This enabled analysis of volumetric data to explain the evolution of the British Pendulum Value of the grooved surfaces as they were trafficked. The Volume of Material in the Peaks was found to relate to the micro-texture surface of the aggregate. A Step Height analysis assessed how groove and rib dimensions evolved. The width of the asphalt rib does not change when subjected to simulated trafficking; however, the height of the rib decreases. This decrease will reduce the water evacuation capability of the grooved surface. This method integrated into a runway monitoring plan would strengthen the asset maintenance plan of the runway.
Significant ambiguity was found in the current EN 13036 test method for determining skid resistance of grooved surfaces. Published research utilising the British Pendulum Tester for grooved surfaces has consistently omitted reference to an important adaptation to the method. New research within this thesis has significantly contributed to the knowledge of the interface between the British Pendulum Tester and a grooved surface. This work identified the pendulum slider bounces across the grooved surface and that pendulum values are based on 57% less contact when not measured according to the adaption within the method.
Based on this work, it will be recommended that the existing method be revised to eliminate the ambiguity and provide clarity to the method. The adaption to the method in this work led to a novel approach to trafficking GMA at an alternative angle to that typically adapted in practice. This simple approach demonstrated favourable pendulum data, with GMA sawn at an angle of 6 degrees to the direction of trafficking, offering higher pendulum value longevity than that typically used in practice (0 degrees).
Rubber accumulation of the runway surface is detrimental to the friction of the surface, particularly during wet conditions. The thesis found that information relating to the theory of rubber deposition on runway surfaces is limited. Rubber is deposited on the runway surface when an aircraft lands on the runway surface due to the impact temperature generated at the tyre pavement interface when the tyre makes contact with the runway surface. A scaled experiment simulated within the constraints of a laboratory environment the process of a landing aircraft tyre touching down on the runway surface. The investigation generated 396 temperature data sets.
Whilst not a direct comparison, the method is similar to what happens in reality. The experiment explored how parameters such as surface texture, aircraft speed and tyre load contribute to impact temperature. It was found that landing speed contributes greatest to impact temperature during landing conditions.
The data applies to aviation industry scenarios, and the new test methods developed have the potential to offer insight into the performance of grooved surfaces.
|Date of Award||Feb 2023|
|Sponsors||Department for the Economy|
|Supervisor||David Woodward (Supervisor) & Phillip Millar (Supervisor)|
- Skid resistance
- New methods