Method for monitoring scour depth of pile foundations based on modal identification

Abstract

The monitoring of scour depth is an important link in the later maintenance of offshore wind turbines. However, existing monitoring equipment and methods must be operated underwater and are greatly affected by currents and waves. A monitoring process that can be carried out above water would be safe and convenient. Therefore, a new scour depth monitoring method was developed in this study. Because the scouring causes the modal of pile foundation to change, the proposed method identifies the modal information obtained from the acceleration signal above the water surface to calculate the scour depth. This method breaks through the current situation that the existing modal detection technology is only applicable to the field of structural damage, and the existing modal detection technology ignores the influence of the characteristics of the soil foundation. The pile foundation and surrounding soil are constructed into a vibration system, so that the change of the soil state is reflected in the modal information of the pile foundation. Then the scour depth can be identified by the model updating theory. Comparison between the calculated results and the pre-set scour depth indicates that the monitoring method was able to identify the scour depth conveniently and stable.