Mechanistic-Empirical Design Method

The most advanced pavement structural design uses a mechanistic-empirical method approach. Unlike an empirical approach, a mechanistic approach seeks explaining phenomena by reference to physical causes. In pavement design, the phenomena are the stresses, strains and deflections within a pavement structure, and the physical causes are the loads and material properties of the pavement structure. The relationship between these phenomena and their physical causes is typically described using a mathematical model.
Various mathematical models we can use.

Along with this mechanistic approach, empirical elements are used when defining what values of the calculated stresses, deflections strains and result in pavement failure.
The relationship between physical phenomena and pavement failure is described by empirically derived equations that compute the number of loading cycles to failure. The basic advantages of a mechanistic-empirical pavement design method over a purely empirical one are:

* It can be used for both existing pavement rehabilitation and new pavement construction.
* It accommodates changing load types.
* It can better characterize materials.
* It uses material properties that relate better to actual pavement performance.
* It provides more reliable performance predictions.
* It better defines the role of construction.
* It accommodates environmental and aging effects on materials.


A mechanistic-empirical approach can also accurately characterize in situ material (including subgrade and existing pavement structures). This is typically done by using a portable device (like a falling weight deflectometer) to make actual field deflection measurements on a pavement structure to be overlaid. These measurements can then be input into equations to determine the existing pavement structural support and the approximate remaining pavement life. This allows for a more realistic design for the given conditions.


So, expert knowledge is required to use mechanistic-empirical approaches; a pavement design expert should be consulted if you are considering its use