FIELD STUDY OF THE STRUCTURAL BEHAVIOUR OF PARTIALLY BONDED RIGID OVERLAYS OVERLYING RIGID PAVEMENTS

Abstract

Rigid overlays have been economically used to strengthen and/or improve the riding surfaces of airfield and highway pavements. Their performance has been reported, based on accelerated traffic tests carried out At different airfields. Based on these performance studies, certain emperical formulae are recommended for the design of overlays in case of airfield pavements. In this investigation} partially bonded rigid overlays overlying rigid pavements have been tested to ascertain the validity of the recommended f ormula in three critical load positions viz„ interior, edge and corner. The study includes the observations of both deflections and stresses under static loading. Westergaares theoretical approach to pavement design assumes the subgrade material to be fully elastic, behaving like a liquid. This being not realised in practice, the basic thinking makes "a slab after repeated deformation remains in contact with the soil" needs a correction, There► fore, firstly, monolithic slabs of two different thicknesses have been tested and new equations have consequently been worked out resulting in more realistic design of pavements. These equations have been used to determine from the overlay data the equivalent sitgle slab thickness that each overlay represents. Based on the equivalent single slab thicknes6 thus worked out, design equations for partially bonded rigid overlays have been recommended for all the three critical load positions. It has been observed that while interior position satisfies the partially bonded equation recommended by U.S. Corps of Engineers, the edge and corner satisfy their equation for unbonded overlays.