Evaluation of Pavement Design in Virginia Based on Layer Deflections, Subgrade and Its Moisture Content

About the report:

In this investigation, the optimum structural strength contributed by a material to the overall strength of the pavement was studied for cases applicable to Virginia. The variables were (a) the modulus of elasticity or the thickness equivalency of the material, (b) the thickness of the material in the layer, (c) the location of the material with respect to other layers containing stronger or weaker materials and in varying thicknesses, and (d) the effect of the total pavement thickness and the depth of the material from the top of the pavement. The investigation consisted of two parts: (a) a study of the thickness equivalencies of the materials on interstate, primary, secondary and subdivision roads in Virginia, and (b) a model study. The evaluation of the highway system was quantitative, while that of the model study was qualitative only. This investigation showed that the structural strength of a pavement is decreased when a weaker layer is placed over a stronger layer or when a weaker layer is sandwiched between two strong layers. The investigation also showed that when the bottom of the top layer does not bend, the stress distribution is bulb type; and when the bottom bends, the stress distribution is fan type. Each case would therefore need a different mathematical treatment for design.

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