De nieuwe generatie Maasstuwen

Abstract

The weirs in the river Meuse reach their theoretical lifespan. The weirs were built in the early 1930s and now one is faced with a replacement task. Various studies have been carried out in recent years on the future of the weirs in the river Meuse. This concerns research into the entire weir system, different types of weirs and the way in which the current weirs should be replaced. This study does not focus on one specific task, but focuses on various aspects that are important for the replacement task, both “soft” and “hard” technical aspects. The first aspect is to find a suitable assessment framework that a new weir must meet. This assessment framework has been developed by means of literature research and interviews with specialists from Rijkswaterstaat, resulting in a risk and opportunity plan especially for weir structures. The assessment framework thus forms the basis for finding both a suitable weir type and a suitable solution for construction. A variant study has been carried out into different weir types. The considered weir types are delineated into a conventional variant, the flap weir, and three innovative variants, namely variants with inflatable technology. The steel-rubber gate, also known as the Obermeyer weir, scores best. This weir type consists of air-filled bellows that inflates and deflates the flaps. It is distinctive in terms of discharge capacity, nuisance and ease of maintenance.
The next phase is to make a conceptual design. A new weir regime has been developed on the basis of several considered weir configurations. A weir configuration with two weir spans of 50 m weir, each with 5 separate flap-bellow components has been designed. Furthermore, the weir sill has been designed with a length of 34 m. Based on the design loads on the bottom, a soil protection has been designed. A block mattress with a geotextile as a filter proves to be a suitable soil protection. The downstream length of the bottom protection is designed as a total of 50 m. Thereafter the forces in the membrane are determined, after which a suitable type of membrane is designed.
The last phase of this research focuses on finding a suitable solution for construction for the new weir in Linne. Three different construction methods have been developed, in-situ, side channel and prefab. For each method, the (global) weir dimensions are verified for the governing load situations. Ultimately, a suitable construction method is selected on the basis of an overall cost indication and assessment criteria, derived from the assessment framework that has been compiled in the first phase. Construction variant C, the prefab solution, scores best. It is an innovative solution in which the entire weir, including flap and bellow elements, is built in a construction dock upstream of the current weir and then transported using pontoons with winches. The major challenges of this construction method are the floating transport where the enormous weir construction must not be damaged, the coupling of the air supply pipes to the compressors in the abutment underwater by divers and the guarantee of a good transfer of forces from the weir sill to the bottom. On the other hand, there is considered to be a great advantage over the other variants in terms of, among other things, costs and construction time. The solution is therefore proposed as the implementation solution for the Obermeyer weir to replace the current weir in Linne.
In addition to this study, a strategy has been developed to deal with uncertainty in design as a depth study. The case of the bottom protection for the new weir has been used to apply this strategy. Different stability relations have been compared that come to the required nominal stone diameter. Based on a consideration of the impact in costs, impact on failure and risk mitigation measures included in this strategy, a broadly-based choice can be made for the design of the soil protection.