Intelligent hydraulic deign of tunnel type sediment excluders

The sediment excluders are provided on the barrages or diversion weirs in the river pocket adjacent to the head regulator to minimize sediment entry in to the canal water. On rivers, the excluders have to deal with alluvial material being transportd by the river. Excessive sediment load can cause damage in a variety of ways which result in many serious problems such as meandering of stream, reduction of channel capacity, silting up of canal, damage to power units and obstruction to navigation. Different types of sediment extractors/ excluders, such as tunnel type, vortex tubes, rectangular settling basins and vortex type settling basins are ofthen employed for this purpose. A tunnel-type sediment excluder is commonly used at the headwork of a canal for preventing excess sediment entry in to the off-taking canal. In such type of excluders, the sediment-laden water, which flows mainly near the bed, is made to flow through the tunnels provided at the bed and the sediment-free water in the top layers is allowed to enter the off-taking canal. It may be then discharged back into the river downstream through the undersluice bays. Comparatively sediment-free water in the top layers is allowed to enter the canal. The only hydraulic principle utilized in its design is that energy loss is kept to a minimum and a minimum velocity of flow is ensured through the tunnel for the non-deposition of the coarse material
In the method recommended by Garde and Pande (1976) and Kothyari (1999) for design of tunnel-type sediment excluders, the main objective is to design a tunnel which is able to flush maximum of sediment load through the tunnel by minimum of excluder discharge and minimum of blockage hence considering all restrictions and constraints for design of such structures.
In the current research it was tried to achieve an optimum design using fuzzy logic abilities and searching the solution domain by an intelligent search method (Genetic Algorithm) which is able to pass the local optimums and find the global optimum. GA considers many points in the serach space simultaneously and has been found to provide a rapid convergence to a near optimum solution in many types of problems. Then optimal designs of GA and Direct-Search method were compared with some of projects in India (i.e. Ganga, Sarda and Eastern Kasi) which were design using traditional methods. A fuzzy AHP (Analytic Hierarchy Process) approach was used for assessing the weight of efficiency, blockage and sediment excluder discharge in goal function. AHP is particulary usefull for evaluating complex multi attribute alternatives involving subjective criteria.The fuzzy AHP approach allows a more accurate description of the decision making process. The triangular fuzzy numbers were used to build the comparision matrices of AHP based on pairwise comparision technique.The results show that the Genetic Algorithm method gives better results in compare with direct search technique. The result also show that the efficiency of tunnel-type sediment excluders are high enough in both optimal design and traditional methods, but sediment blockage percent in propose optimal design is less than correspond design values using