Some Recent Findings In Flexible Pavement Research

This paper is based on sponsored research done by the Texas Transportation Institute on Texas highways. The results reported include: (1) The development of an empirical equation for estimating load-induced deflections from the thickness and laboratory-determined strength of the materials used in a highway pavement, and (2) the use of the equation, together with deflections observed on 323 highway test sections, to evaluate the regional effect in Texas. With a surprisingly large regional effect determined, the net result of the research was an equation for deflections that contained: (1) a Field Compression Coefficient for each layer dependent on both laboratory strength and regional effect, and (2) a Depth Coefficient for each layer dependent upon the thickness of the layer and its position in the structure. The equation presumably could be used in the design of flexible pavements in Texas if deflection criteria were made a part of the design procedure, and if the underlying causes of the regional effect were known.