Critical Tensile Strain in Asphalt Pavements

Charts based on two-layer elastic theory are presented for determining the critical tensile strain at the bottom of the asphalt-bound layer under single, dual, and dual-tandem wheels. They can be applied directly to full-depth asphalt pavements where only two layers are involved. For a conventional three-layer system, a method is developed to convert it into an equivalent two-layer system, so that the charts can still apply. A comparison of the critical tensile strains obtained from the charts with those determined directly from a computer program clearly indicates that they are accurate enough for engineering applications. Examples are given to illustrate the use of these charts for determining the critical tensile strains in two-layer and three-layer pavement systems. It is found that for a given pavement type and tire configuration there exists a critical thickness of the asphalt-bound layer at which the greatest tensile strain is obtained, and that the critical tensile strains under dual-tandem wheels are generally smaller than that under the dual wheels alone.