Parametric design-tool to optimize preliminary design of navigation lock chambers

Abstract

Summary
In the twentieth century a substantial number of navigation locks were build in the Netherlands. The navigation locks built in that era mostly had a life span of 80 to 100 years. This means that in the coming years most of these locks will be in need of either renovation or replacement. Rijkswaterstaat, the administrator of most of the locks in the Netherlands, is likely to put out tenders for the renovation and replacement of these locks. Companies can subsequently submit a proposal for design and/or construction. This proposal includes a preliminary design of the lock. During this phase of the design multiple possible alternatives will be reviewed to check which of those satisfy the design requirements and how they will be implemented. The time available to create a proposal is limited and the preliminary design phase is time consuming due to the numerous design alternatives available. Therefore, several alternatives are often not elaborated, which already leads to converging in the design process in an early phase. When the time needed to create a design of the alternatives can be reduced, the converging can be postponed to the detailed design and more attention can be paid to out-of-the-box thinking during preliminary design. This time saving can be accomplished by the use of automation and parametric design. With parametric design all the possible alternatives can be calculated in a given range of parameters. After comparison of these generated alternatives a well-educated choice can be made for the direction in preliminary design. This research aims to optimize preliminary lock design in the tendering phase by creating a design-tool that automatically generates all plausible alternatives based on the Design Criteria and boundary conditions of the client.
Eventually, the complete preliminary lock design can be accomplished with a parametric design tool. However, an advantage of a design tool is that it can be composed of different building blocks which all design a specific part of the navigation lock. The basis of the parametric design tool should be a relevant part of the lock when looking at the total costs of this part, the design costs, the variety of options and the relation with other parts. The lock chamber is chosen as a starting point for the design tool. The lock chamber, like the lock head and the mechanics, has high investment costs and a high percentage of design costs. The lock chamber however, is in contrast to the other parts of the lock, not heavily dependent on other components. This makes it an interesting component to make a parametric design tool out of.
The parametric model, that has been developed as a part of this thesis, includes the commonly used chamber types for inland navigation locks. These common types are retaining wall structures with an under water concrete floor including sheet pile, combi and diaphragm walls, and a U-basin structure, which can be constructed in an open building pit or in a temporary retaining wall building pit.
When the design tool is finished, research is conducted on the behaviour of the alternatives in different circumstances. The effects of the main design criteria are examined. These include the length of the chamber, width, depth, water drop and local soil profile. These values are mostly depended on the vessels that need to be accommodated and the local circumstances. Next to that, the impact of different construction methods, the use of materials and the variation in unit prices are elaborated.
In this thesis the second Juliana lock near Gouda is used as reference case. For this case it has been found that a sheet pile wall structure is economically most attractive, followed by the U-basin with an open building pit, a diaphragm wall structure and least feasible a U-basin structure with a retaining wall building pit. It is concluded that the length of the lock does hardly impact the design of the alternatives. The width of the chamber does influence the dimensions of the structure. The floor has to be stronger for larger widths and, because of this, the diaphragm wall structure will become more attractive compared to the U-basin structures. The depth and water drop mainly impacts the dimensions of the walls. This, combined with the increased soil handling with open building pits, leads to decreasing interest in U-basin structures. When looking at the construction methods and materials, it can be noted that the length of the tension piles is especially important for the pile plan and the floor. The concrete strength for the U-basins is of importance, while the under water concrete strength and the casting method hardly influence the total costs.
When looking at environmental impact, the alternative with the least material use is most attractive, the sheet pile wall structure followed, by the diaphragm wall structure. The type of material does heavily influence the environmental impact. The U-basin structures have more environmental impact due to the construction of a larger temporary building pit. The environmental impact consists of three main components, the used materials, transport of these materials and the processes for the construction of the lock. For the U-basin structures the last two components have a large impact, while for the retaining wall structures the materials used have a large footprint.
The proposed CO2 taxes of € 0,05 an €0,20 per kg CO2 equivalent will lead to an average cost increase of respectively 4,5% and 16.5%. The impact per alternative differs, but does not influence the order of economical feasibility. As from a CO2 tax of € 0,68 per kg CO2 equivalent the diaphragm wall structure will become financially more attractive compared to the U-basin structure with open building pit.
Despite the calculated strengths and costs, each structure has its own advantages, disadvantages and limitations in construction, final use and maintenance. Special attention should be paid to these properties, since certain construction methods may be excluded by design requirements and uncertainties can lead to high risk. Further research could focus on steel sheet or combi piles constructed in bentonite excavations, resolving the limitations of vibrations during sheet pile construction and the uncertainties of diaphragm walls.