In flexible pavement design, what is the distinct function of the granular base layer that differs significantly from its role in a rigid pavement system?

In a flexible pavement system, the distinct function of the granular base layer, which is typically composed of crushed stone or gravel, is to significantly contribute to the structural capacity by actively distributing traffic loads over a wider area to the underlying subgrade. Flexible pavements, such as those made with asphalt concrete (AC) or hot mix asphalt (HMA) as the surface layer, rely on a layered system where each layer progressively spreads and reduces the stress exerted by traffic. The asphalt layer, being flexible, deforms under load and spreads it conically. The granular base then acts as a crucial load-spreading layer, taking the load distributed by the asphalt and further disseminating it over a larger footprint, thereby reducing the stress intensity on the weaker subgrade to an acceptable level. This structural rol....