Microwave Structural Health Monitoring of the Grouted Connection of a Monopile-Based Offshore Wind Turbine: Fatigue Testing Using a Scaled Laboratory Demonstrator

Figure 11

Evolution of the visible damage on November 22 at two opposite sides of the demonstrator (90° and 270°). Small radial surface cracks are visible immediately after curing, with a wet circumferential crack appearing at the 270° position by 12:09 UTC (indicated by a yellow arrow). At 12:14 UTC, water starts escaping from one of the radial cracks at the 90° position. At 12:26 UTC, a growing volume of water surfaced from the cracks, gradually filling the area above the grout, leaving only the water surface visible. The water surface remains visible until 15:27 UTC when most of it disappears, leaving the surface still wet. At 16:18 UTC, the surface dries up further.