Pavement Design Term Paper Example | Topics and Well Written Essays - 500 words

Pavement Design - Term Paper Example The Structural Number is a value that applies to the overall  pavement structure, but for a complete design it is a prerequisite to get from this value to the individual layer thicknesses. This is handled using an equation of the type shown: and can be adapted to any number of pavement layers, since each expression (such as a2D2M2) in the formula corresponds to a single layer, so that the variables in the expression correspond to the characteristics of that layer. The subscript number used in the expression simply indicates which layer is meant, with the numbering beginning at the top of the pavement structure. The variables represent the following: The layer and drainage coefficients are values that should reflect characteristics of the material used to construct that pavement layer. The thicknesses of the individual layers are effectively what is used to design equation, and the Structural Number, to figure out. Since the layer coefficient represents the strength of the material, this is the primary variable that factors in the type of material to use for each layer. For design purposes, layer coefficients are typically determined empirically based on the performance of the material. Agencies often set specific layer coefficient values for commonly used materials as a standard design policy. Some typical layer coefficient values are:Hot mix asphalt – 0.44, road mix (low stability) – 0.20, aggregate base – 0.13, engineered fill – 0.10 Since the layer coefficient can be affected by material properties as well as the position of the layer in which the material will be used, in some cases different values might be appropriate for local conditions. A drainage coefficient is a value assigned to a pavement layer that represents its relative loss of strength due to  drainage characteristics  and exposure to moisture saturation. Layers that