Focus on…onsite testing

Testing equipment

The latest “Focus on…” looks at how we test the ground formation before starting each foundation. It’s called a plate bearing test, and this is how we do it….

What is a plate bearing test and what does it tell us?

A plate bearing test measures settlement under load on the ground to determine whether the ground has sufficient bearing capacity. In simplistic terms, it determines whether the ground is structurally sound enough to withstand each turbine at the proposed location, as well as the weight of the machinery needed to install them.

The plate bearing test

To complete the test, a circular plate 500mm in diameter is loaded by hydraulic jack. The plate is pressed down onto the ground to test the settlement of the material – when the pressure is applied, a measurement can be taken to determine the amount of displacement  or movement in the ground formation in increments of less than a millimetre.  This test data is plotted on a graph to examine the relationship between the bearing pressure and settlement of the ground formation. With this information the engineer can determine whether the ground formation is good enough to continue to the next construction phase or if it requires further work.

Testing equipment

Testing equipment

When is it done?

We use this test on the ground formation at each turbine location before we start laying the steel & pouring the concrete foundations. We also test the crane hardstandings before any machinery is used on them, including the concrete pumps and the cranes used to lift in the steel reinforcement and eventually the cranes used to install the turbine components.