Optimal Economic Design of Diversion Structures during Construction of a Dam by Particle Swarm Optimization

Diverting river flow during construction of a main dam involves the construction of cofferdams, and tunnels, channels or other temporary passages. Diversion channels are commonly used in wide valleys where the high flow makes tunnels or culverts uneconomic. The diversion works must form part of the overall project design since it will have a major impact on its cost, as well as on the design, construction program and overall cost of the permanent works. Construction costs contain of excavation, lining of the channel, and construction of upstream and downstream cofferdams. The optimization model was applied to obtain optimal channel cross section, height of upstream cofferdam, and height of downstream cofferdam with minimum construction costs for diversion works which is solved by PSO method using MATLAB. The optimization model was applied to prepare the optimal design graphs. It can be noticed, at any design flowrate, optimal water flow depth, bed width, and height of upstream and downstream cofferdams decrease with increase of the side-slope. Also, it can be observed, at any design flowrate, the construction cost increases with increase of the side-slope.