Road bearing capacity (FWD)

When determining the bearing capacity of the road structure, we use the Dynatest FWD-8002 load device with falling weight, which is used for testing flexible, composite and rigid pavements. Dynamic loading devices, among them the Dynatest FWD-8002, are widely used in the world and it is one of the few measuring devices that allows to study the road structure without breaking it. The device simulates the load caused by the wheel of a moving truck by dropping a load with a certain weight from a certain height onto a 300 mm diameter load plate.

The deformation of the road surface caused by the load (the so-called sinking bowl) is measured with seven sensors, one of which is placed at the center of the load plate and the rest at a distance of 300, 600, 750, 900, 1200 and 1500 mm from the latter, respectively. The deflections measured by the sensors are recorded and stored in the computer.

The determination of the general E-module of the pavement based on the measurement results of the FWD device is based on the results of the research paper “Methodical Basis for the Evaluation of Pavement Structural Strength in Estonian Pavement Management System” completed in 2003 by Dr. A. Aavik.

The FWD device can be used:

• to compare the values ​​of subsidence and the shape of the subsidence bowls;
• to determine the bearing capacity (general modulus of elasticity of the pavement);
• to determine the modulus of elasticity of the different layers of the pavement.

The more precise the final results are, the more accurate and specific the source data must be. For example, to determine the modulus of elasticity of different layers of the pavement, it is necessary to know their thickness, which requires drilling or ground radar surveys.

The Dynatest FWD-8002 device has regularly participated in pan-European comparison testing of FWD devices in the Netherlands and Germany. Comparison tests confirm that the measurement results of the device are comparable to the measurement results of other similar devices across Europe.