Non-iterative design method for flexible channels with bends

Flexible linings provide a means of stabilising roadside channels. These linings conform to potential changes in channel shape while maintaining overall lining integrity. The current design method of flexible linings is based on trial and error and typically involves three sets of iterations. The method becomes extremely complex when lining type and channel dimensions are to be modified to satisfy three design criteria: discharge, permissible shear stresses and side slope stability. This paper presents an optimisation model that directly provides the best channel lining subject to the design criteria. The proposed model can handle a large number of constraints, and provides the optimal solution in seconds using the Excel Solver software. The model is developed for riprap, cobble and gravel linings. The user needs to specify available stone sizes, and then the model selects the best size for channel straight and curved segments. The application of the model is illustrated using numerical examples, and sensitivity analysis is performed. The proposed model has been validated by comparing its results with those of the trial method. The proposed model provides efficiency and flexibility in the design of roadside channels, and should be a useful design tool of interest to practitioners and researchers.