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Developing a measuring & monitoring strategy for dikes reinforced with innovative anti-piping filter solutions

Vermeulen, K.R. (2023) Developing a measuring & monitoring strategy for dikes reinforced with innovative anti-piping filter solutions.

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Abstract:Problem - Backward Internal Erosion Piping, called piping in the Dutch context, is a dike failure mech­anism caused by a process by which seepage forces gradually erode cohesionless material from the foundation of dikes, thereby forming shallow pipes at the interface of the granular material and a co­hesive cover layer. One new innovative type of reinforcement measure to increase the resistance of a dike to the piping failure mechanism are filter solutions. These solutions work by blocking the soil particles in the seepage paths with an erosion-resistant permeable filter, preventing the formation of a full-grown pipe erosion channel. The purpose of an erosion-resistant filter is to prevent erosion while also enabling the discharge of seepage, unlike anti-piping heave screens, which do not enable seep­age of discharge. HDSR, a water authority with dikes, is implementing a new innovative filter screen solution as part of a pilot project. While HDSR as a water manager with dikes, is experienced with pip­ing as a failure mechanism, with implementing these innovative filter screens, there is no experience. Given the innovative nature of these filter screens, long-term monitoring might be an option for HDSR to implement and increase confidence in the chosen filter screen solution. Relevant knowledge on how a monitoring plan can be created to monitor the long-term functionality of a filter solution is lacking, and additionally, it is unclear how the three different filter solutions available, vertically inserted geotextile, course sand barrier and Prolock, differ from each other in monitoring possibilities. As water manager with dikes, HDSR, therefore, desires an improved understanding of the long-term risks of failure of the various anti-piping filter solutions and the role of monitoring in risk mitigation in order to ultimately develop and manage measuring & monitoring systems to monitor the continued functionality of a filter throughout the management life cycle phase of a dike. Goal - In this research, a measuring & monitoring strategy for innovative anti-piping filter solutions is developed. A measurement and monitoring strategy should be able to provide insight into the continued functionality with regard to piping of the filter screen during the management life cycle. The research is requested by HDSR and is, therefore, the primary stakeholder of this research. The target group, in general, are water managers of dikes (to be) reinforced with an anti-piping filter screen. HDSR is a part of this target group as; currently, the Sterke Lekdijk is to be reinforced with a new filter screen solution Prolock. This study is requested by HDSR as a second opinion for the designed monitoring plan, while they also wish to gain insight into the different filter solutions available and differences in monitoring these filters: Vertically Inserted Geotextile, Course Sand Barrier, Prolock. The following research goal has been formulated: To design a measurement & monitoring strategy to monitor the continued functionality of a filter as an anti-piping measure during the management life cycle phase of a dike. Methododology- This research consists of a design problem, and therefore, an appropriate iterative de­sign cycle methodology is chosen. While the methodology is theoretically iterative, only one complete iteration has been performed. The methodology consists of three (iterative) phases, problem investiga­tion, where a theoretical framework is established. Additionally, the target group is interviewed to set up the requirements of measurement & monitoring strategy within its intended problem context: creating location and filter-specific measurement & monitoring plans for innovative anti-piping solutions by the target group (water managers with dikes). The second phase is the design phase, where using the results of the problem investigation and an analysis of the different filters, failure modes and monitoring options, a monitoring strategy is designed. In the final iterative phase, the validity of the final design product is assessed through verification of design requirements, target group satisfaction and expert opinion interviews. Results and discussion - The final result can be captured in one large diagram as part of a monitoring strategy. The essence of this diagram is that when assessing possible monitoring options, these are measures part of many different measures taken or assumptions made to decrease the failure of the filter. With consideration of all these measures/assumptions that may or may not have been taken and the project and site-specific circumstance, a well-considered decision can be made for implementing a monitoring option. The diagram shows which causes of failure monitoring can contribute to their risk reduction, as well as insight into the differences and similarities between the three different filters. The failure scenarios are also a way of making many different causes of failure comprehensible, requiring reading through all documentation or having extensive knowledge of all three filters. One of the main discussion points of this research is that according to expert opinion the final monitoring options listed may currently not always be practically feasible due to unfavourable cost-benefits ratios or measure­ment uncertainties. However, as also stated during expert opinon sessions, this a current temporary problem as monitoring technologies are expected to improve on all aspects, such as costs and accu­racy, in the future. Additionally, due to the filter generic approach, without location and project-specific circumstances, no definitive recommendations on monitoring can be made. However, a the resulting design result, an extensive diagram makes the different failure modes of filter solutions, the differences in these for the three filters, the different risk mitigation measures available per life phase and the mon­itoring possibilities during the management phase all have been made insightful and comprehendible for water managers with dikes, which is the main added value of this diagram and study. Conclusion - It can be concluded that the monitoring strategy and associated diagram are of added value when drawing up a monitoring plan for the various filters. It contains information relevant to a dike manager, and the diagram is logically structured. An important conclusion from the iterative process is that a systematic understanding of how a filter functions, the failure scenarios and the correspond­ing risk mitigation measures are essential to arrive at a well-founded measuring & monitoring strategy. These aspects are therefore highlighted in the monitoring strategy and diagram.
Item Type:Essay (Master)
BZ Ingenieurs & Managers, Deventer, The Netherlands
Hoogheemraadschaap de Stichtse Rijnlanden, Houten, The Netherlands
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
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