A Digital twin, a digital replica of a physical entity or system, encapsulated in a software model, represents a promising technology that has demonstrated its effectiveness for asset management in various industries. Rijkswaterstaat has gained interest in investigating the possibilities for digital twin integration in the asset management of storm surge barriers. Therefore, in this Engineering Doctorate (EngD) research, the application and development of a digital twin for a storm surge barrier is investigated, with the Maeslant barrier serving as the case study. Storm surge barriers are technically complex systems that fulfil a vital role in the flood protection of the Netherlands. A strict form of risk based asset management (ProBO) is applied to keep the barrier operational. However, the complexity and infrequent use of the barrier makes this form of asset management highly knowledge intensive. Currently it is a large asset management challenge for Rijkswaterstaat (the organization responsible for operation and maintenance of the storm surge barriers in the Netherlands) to maintain the necessary expertise at the right level. The goal is therefore to explore the following question: “How can a prototype digital twin support in investigating the application of a full-scale digital twin for storm surge barriers, to strengthen the knowledge and information in support of their maintenance and operations?” A prototype of a digital twin for the Maeslant barrier has been designed and constructed by the writer of this report, with a particular focus on the barrier’s retaining walls. For the design of this prototype (see Figure 1), knowledge from three fields had to be integrated: 1) organizational & user needs; 2) functioning of the barrier (civil and mechanical engineering); 3) ICT architecture design. As a first design step the user needs were investigated by conducting interviews with Rijkswaterstaat employees. These were translated into four applications the digital twin should fulfil to provide added value: 1. Enhancing efficiency in knowledge and information management 2. Avoiding unnecessary costs through better barrier status monitoring 3. Improving risk management with models and data analysis 4. Providing insights into barrier behaviour The user requirements were translated into design requirements to build the digital twin prototype, which is developed using Unity and Python scripts. The scripts are used for data calibration purposes and to make a connection between the digital twin model and existing models. For this prototype, a connection is made with a hydrostatic force model, a failure probability model and a pump discharge model. The Unity model acts as the user interface for the digital twin model in which a 3D data animation model of the barrier is integrated combined with data visualization panels. The functional application of the prototype is illustrated by means of three use cases: • Case 1 - Analysis of closing procedures based on observations. Quickly accessible and direct available data put users in the position to analyse the barrier closures and monitor its status by means of data visualisation, animation and model calculations. • Case 2 - Knowledge conservation and transfer: hydrostatic forces example. Increasing knowledge transfer, illustrated by an example in which hydrostatic forces acting on the barrier are animated and supplemented with visualized data that can be analysed. • Case 3 - Observing abnormal behaviour and including risk management. Using the digital twin to observe abnormal pump performances and directly calculate the impact of possible measures on the failure probability, to avoid unnecessary quick and costly decisions. The prototype is tested among 14 potential users within Rijkswaterstaat to investigate the perceived added value and the organizational feasibility of a full implementation. The results of the tests demonstrate that digital twin users recognize clear value to enhance knowledge and information management. The current prototype exhibits potential in this regard, especially for the sake of information sharing and education, suggesting significant possibilities for a full-scale (i.e. of the entire barrier) digital twin. In the long term, it is expected that the digital twin could add value in increasing the barrier’s asset management. An important notification, however, is that the reactions of respondents was diverse. The respondents with a more practical role at the barrier (e.g., the operational technical specialists) were less enthusiastic about the prototype for direct use for asset management than the higher management. The development of the prototype demonstrated the feasibility of a small-scale digital twin of the barrier. However, it does not guarantee a successful implementation of a full-scale digital twin within the Rijkswaterstaat organization. Therefore, the challenges and obstacles in implementation have been further investigated through a technical, economic, and organizational feasibility study. The prototype indicates that the available technology in the market, both at hardware and software level, is sufficient to develop a full-scale digital twin for the Maeslant barrier. However, the current state of hard- and software within Rijkswaterstaat is insufficient for full-scale implementation. Especially on cyber security, challenges need to be overcome to be able to use the maximum capacity of a full-scale digital twin. A full-scale digital twin is expected to be financially feasible: a business case study indicates that a digital twin could be cost effective within five years. The economic added value of the digital twin is estimated based on expected savings in time and maintenance cost for Rijkswaterstaat. The costs are estimated by extrapolating the development cost of the prototype. The Maeslant barrier organization is, resulting from the questionnaire, enthusiastic about implementation of a full-scale digital twin. However, achieving a digital twin with added value to the entire organization necessitates further development of the existing prototype, and a better connection to the user needs of the respondents that rated the prototype less positive. Subsequently, for successful implementation, the technically oriented Rijkswaterstaat employees need to be heavily included in the development process and must be given time to support in the implementation. All points considered it is concluded that a full-scale digital twin is, under reasonable assumption of several surmountable challenges, feasible to implement for the Maeslant barrier. @en

As part of the SAFElevee project Delft University of Technology collabored with Flanders Hydraulics Research, and Infram B.V. in the preperation and execution of a full scale embankment breach experiment in November 2015. This breach experiment was performed on an 3.5m high embankment with a sand core and clay outer layer situated along the tidal river Scheldt in Belgium near Schellebelle. During the experiment a wave overtopping simulator and overflow simulator were used to initiate a breach. Both simulators were placed near the top of the waterside slope. The use of the simulators facilitated comparison between the effects of continueous overflow and the effects of intermittent wave overtopping. This paper presents the data collected during the experiment, describe the development of hypotheses on the failure processes using the latest insights, and comment on the failure initiation process of a grass covered flood embankment with a clay outer layer and a sandy core.@en