Foundation Monitoring – An Overview of Methods and Measurement Solutions

Company / Unternehmen: Airwerk
Speaker / Referent: Jens Krieger (1), Jörg Bendfeld (2)
Position: Technical Director

The offshore wind energy industry is still relatively young. There is little or simply not really sufficient experience regarding the safety of the wind turbine foundations; the material stress due to wind and waves is still not completely clear. The same is true for the load bearing capacity of the ocean soil. For example, the effect of cyclic loads is of great concern to the industry. A continuous foundation monitoring including analysis is therefore needed. Offshore foundation monitoring projects are typically initiated in response to the BSH requirement to equip 10% of all offshore structures with a foundation monitoring system. There are also projects involving the establishment of the observation method as specified in DIN 1054 / EC7 in response to situations in which the statical integrity can’t be ensured via static analysis. Furthermore, there are often additional individual measurement requirements for each offshore wind farm project.

Foundation monitoring concepts should include:
– Prognosis of the probable structure behaviour
– Determination of the limits of the allowed structure behaviour
– Definition of a measurement program (sensors, installation, maintenance, data handling, data analysis, documentation of measurement program)
– Definition of corrective measures to ensure the structure stability in case of alarming measurement results
– It must be shown corrective measures can be implemented in time to ensure structure stability.
– Documentation of the execution of the measurement program

There is not yet a standard concerning the scope of offshore foundation monitoring projects. Realization details depend on wind park project specifics such as foundation type, water depth, soil conditions, etc. Another important issue is whether the proposed monitoring program should fulfil the basic BSH requirements only or whether the park operator would like to have additional structure information vital to park operation (e.g. grout monitoring).

Typically, foundation monitoring includes:
– Scour monitoring
– Grout monitoring
– Inclination monitoring- Load monitoring
– Acceleration monitoring
– Monitoring of turbine position
– Metocean sensors

The presentation will give an overview about the topic and typical realizations of measurement programs for offshore foundations.

(1) airwerk GmbH, Industriering 14, 49393 Lohne, Tel.: + 49 (0) 201 12516907, Fax: + 49 (0) 201 12516926,, Lohne, Germany
(2) University of Paderborn, Kompetenzzentrum für nachhaltige Energietechnik KET, Pohlweg 55, 33098 Paderborn, Germany,