Abstract
Due to urbanization, the infiltration has decreased drastically resulting in more runoff. Due to this, dams are receiving more runoff than the design runoff. To avoid over topping of dams due to this excess runoff, the capacity of the spillways has to be augmented. The objective of this research is to determine the effect of nano material on increasing the discharge capacity of Ogee spillways. Ogee spillways were constructed in a rectangular flume. Experiments were carried on a tilting flume of size 10 m X 0.55 m X 0.6 m. The Ogee spillway model was fabricated and plastered with cement mortar 1:3. Three slopes were used and laboratory experiments were performed with varying heads. Another Ogee spillway was made and plastered with cement mortar 1:3 in which 30 % cement was replaced with nano cement. The discharges for the three slopes (0.003333, 0.007778, and 0.012222) were found for Ogee spillway plastered with cement mortar and also for the Ogee spillway plastered with 30 % of nano cement by varying the heads between 0.5 cm and 5 cm above the crest of the spillway in steps of 0.5 cm. It is found that spillway with 30 % nano cement replacement gives more discharge than the spillway plastered with normal cement mortar. Experimental investigations related to porosity, roughness height and SEM analysis also prove that replacement of nanomaterial improves the surface smoothness and hence increasing the carrying capacity of the spillway.
Highlights
Spillway is one of the most important structural components of a dam
The three major components of spillway are (i) Control structure which admits flow to the spillway (ii) Discharge channel which conveys the flow from the control structure to the stream bed below the dam (iii) Terminal structures are energy-dissipating devices that are provided to return the flow to the river without serious scour or erosion at the toe of the dam
From the study they concluded that, Piano Key Weir (PKW) technology can play a role under the simple fact that it does not inhibit stream flow due to absence of any gate control system
Summary
Spillway is one of the most important structural components of a dam. Spillways function as ‘diverting agents’ for excess amounts of water that is diverted to different canals, thereby the safety of the dams are ensured. Ogee spillway represents the shape of the downstream face of the weir. The profile of the spillway is made in accordance with the shape of the lower nappe of the free-falling jet. Ogee spillways play a major role in energy dissipation effectively and discharge of flood safely over its downstream end. When water falls from higher head to lower head, it produces high amount of kinetic energy at the foot of the spillway and it is necessary to dissipate energy effectively, otherwise it will create scouring, erosion on its chute surface [1]. The Ogee spillway functioning similar to a dam, provides the safe passage of water thereby prevent flooding. In engineering terms, they can be compared in function to safety valves in boilers. Updating the criteria required for safe hydraulic structures to keep pace with the changes in climate and potentiality hazardous after effects on structural integrity and capacity resulted in the need for continuous expansion and up gradation of spillway capacities to increase the discharge [8]
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