🕑 Reading time: 1 minuteThere are various methods of flexible pavement design such as empirical and semi-empirical methods. Flexible pavement design by semi-empirical method is discussed in this article. When a flexible pavement is subjected loading, the stress is maximum at the top layer of pavement. This stress transmits to another layer by point to point contact. Design of flexible pavement is done to bear the all stresses subjected on the top layer.
Flexible Pavement Design by Semi Empirical MethodFollowing are the semi empirical methods for flexible pavement design
- Triaxial test method
- Burmister’s method
Triaxial Test Method of Flexible Pavement DesignIn this method triaxial test is conducted on soil specimen under 160kN/m2 of lateral pressure. Hence modulus of elasticity is calculated from stress strain curve. Traffic coefficient X and saturation coefficient Y are introduced in this method. These are multiplied with the load system to get the total pavement thickness. Total pavement thickness by triaxial test method Where P = wheel load = design deflection = 0.25cm E = elasticity modulus X = traffic coefficient Y = saturation coefficient The recommended values of X and Y values with respect to Average Daily Traffic (ADT) and average annual rainfall are tabulated below.
|ADT (number)||Traffic coefficient X|
|Average annual rainfall (cm)||Saturation coefficient (Y)|
Burmister’s Method of Flexible Pavement DesignBurmister introduced a semi empirical method for the design of flexible pavements. In this method, he considered pavement as number of layers. And some assumptions are considered which are as follows:
- The material in each layer is homogeneous
- The material is isotropic
- The material is elastic in nature
- Contact between the layers is continuous
- Unloaded top layer is free from normal and shearing stresses
- The surface layer is infinite in length (horizontal direction) and finite in depth (vertical direction).
- The underlying layers are infinite in both directions.