An examination of the affect of axle spacing on the deformation of thin membrane pavements

This thesis examines the affect of axle spacing in large trucks on the deformation of thin membrane pavement and whether the resulting effect should be incorporated into pavement design, maintenance and permitting. Data collected from a test road was analyzed. (1) The pressure analysis shows when axle spacing is ≤1.52m, pressure is compounded in the subgrade. (2) Strain data indicates when axles are spaced > 2.5m apart; the asphalt recovers. When axles are <1.68m apart there is no recovery (compound effect) in the asphalt. (3) The deflection analysis suggests closer axle spacing dampens the propagation of energy waves causing less deflection in the asphalt layer.;Overall analysis proves axle spacing does influence pavement response.;The ideal axle spacing may exist, there is not enough data available to make that determination; further analysis and testing are required. Bridges are a limiting factor in vehicle weights and axle spacing on roadways.