Optimised multi-objective design of weir structures

Abstract

Diversion head works, also called weirs or barrages, are structures constructed across rivers or canals to store water or raise water level. The design of diversion weir structures involves calculating the depth, length and thickness parameters of the horizontal and sloping aprons and sheet pile cut-offs. The design parameters of a diversion weir structure, which have complex non-linear relationships, are determined traditionally using empirically derived recommendations and iterations to achieve structural stability against failures due to scour, uplift, sliding, piping and overturning. However, current design approaches do not explicitly explore the trade-offs between the many relevant design objectives; failing to reveal possibly superior designs. This article proposes a multi-objective optimization design approach for a diversion weir structure. The article also provides a free and open-source code that can be used as a design tool. The method is demonstrated on a stylised design problem. The results show the method reveals solutions with diverse balances of stability metrics and cost; with the optimal relationship of parameter values of components also varying based on the relative cost of sheet pile and apron construction materials. Key Points 1. Current design approaches for diversion structures on permeable media do not explore the trade-offs between the many relevant design objectives, failing to reveal possibly superior designs 2. A design formulation for multi-objective optimization of diversion weir structures is proposed. 3. Multi objective optimization achieves substantial improvement in stability of the structure and cost.