Hydraulic Structures - Research Paper Example

TABLE OF CONTENTS CONTENTS PAGE Introduction 2. Hydraulic Structures 2 Hydraulic Engineering Structures 2 2.1.1 General Hydraulic Engineering Structures 2 2.1.2 Special Hydraulic Engineering Structures 2 2.2 Design of Hydraulic Structures 3 2.3 Different Hydraulic Structures 3 2.3.1 Storage Dams 4 2.3.2 Spillway 5 2.3.3 Outlet Works 5 2.3.4 Diversion Works 6 2.3.5 Drop Structures 6 2.3.6 Stone Structures 7 2.3.7 Conveyance and Control Structures 7 2.3.8 Culverts and Measurement of Flow 7 3. Conclusion 8 References i Appendix A (A Spillway) ii Appendix B (Canal Drop Structure from Lee Lake) iii Appendix C (Bottom Outlet Culvert in a Dam) iv Hydraulic Structures 1. Introduction Water is one of the few natural resources present in the world. It is crucially important for the existence and survival of people, animals, and vegetation. Without this natural resource, no species on the earth can survive. Because of its uneven distribution on earth, it is very important to construct storage dams on rivers in order to make use of river water for various purposes. Tancev (2005, p.3) asserts, “Water plays an exceptionally significant role in the economic development of all countries”. The increase in population of the world has reached a dangerous mark at which quantity of water needed for the human beings, irrigation, and electric power production and the actual quantity of water present in the rivers has become unbalanced. Therefore, various hydraulic structures are developed in order to manage the natural flow of river water. 2. Hydraulic Structures Hydraulic structures are those engineering works that are used to restrict, divert, or store the river water for various purposes. The main function of hydraulic structures is to manage the natural flow of water. The materials that are used in the construction of hydraulic structures include large rock, concrete, and wooden timbers. Hydraulic structures are built in such rivers where the change in natural flow of water is desired. Hydraulic structures are designed and constructed by the civil engineering professionals in order to solve various tasks related to utilization of water. 2.1 Hydraulic Engineering Structures In order to protect the environment from harmful effects of river water, civil engineering professional construct two types of hydraulic structures that are general hydraulic structures and special hydraulic structures. Let us discuss both of these structure types in order to get better understanding of hydraulic engineering structures. 2.1.1 General Hydraulic Engineering Structures The three categories of general hydraulic engineering structures include water retaining structures, water-conveying structures, and intake structures. Water retaining structures are used to retain or raise the level of water by constructing dams on rivers. Water conveying structures are used to create tunnels and elevated structures. These tunnels, channels, or pipelines are known as artificial watercourses. These structures are also used for water navigation purposes and for encompassing spillway and overflow structures. Intake structures serve the purpose of water interception in order to transport it to the public through various water conveying structures. 2.1.2 Special Hydraulic Engineering Structures Special hydraulic structures differ from general hydraulic structures in a way that these are employed in just a part of water utilization branches instead of being employed in all branches. The structures included in the category of special hydraulic engineering structures are special hydropower structures, special water transportation structures, special water supply structures, special drainage systems, special irrigation structures, fishery economy structures, special torrent regulation structures, and sporting recreational structures. 2.2 Design of Hydraulic Structures Design of hydraulic structures is extremely important in order to construct a hydraulic structure. Experts from the civil engineering field play their valuable role in designing a hydraulic structure in a proper manner. Some of the main fields related to design of hydraulic structures include dams, networks for water distribution, networks for water collection of water, and storm water management. Engineers carry out some investigations before designing the hydraulic structures. These investigative works include topographic investigation works, engineering-geological investigation works, hydro-geological investigative works, geotechnical investigation works, geo-mechanical investigation works, hydrological investigation works, constructional output investigation works, and some other investigation works. All of the above mentioned investigation works are critically important in order to design a flawless hydraulic structure. The major constituent elements, which have a great influence on the design of the hydraulic structures, include elaboration and definition of future hydrological regime, schematic structures of the work, hydraulic dimensioning of the structures, seepage calculations for watertight elements, static and dynamic dimensioning, time scheduling, preparing technical specifications for materials’ construction, preparing the bill of quantities, and determination of the total cost of the structure. 2.3 Different Hydraulic Structures There are various types of hydraulic structures that play a great role in the development of a country’s economy. Let us discuss some of those hydraulic structures in detail. These structures include storage dams, spillway, outlet works, diversion works, drop structures, stone structures, and conveyance and control structures. 2.3.1 Storage Dams Dams are used for the storage of river water. Jansen (1988) found that a dam is a wall of concrete that is constructed across a river in order to store water by blocking the flow of the river water. The number of storage dams in a country represents the hydrological and economic development of that specific country. Nalluri, et al., (2003, p.3) stress on the importance of RCC dams and found RCC dams to be the best storage dams with respect to hydrological safety. If we talk about the main categories of dams, we can say that there are two main categories. These two categories include on-channel dams and off-channel dams. On-channel dams are located on the main rivers and upstream watershed fills these dams whereas off-channel dams are not located on the main-stem rivers, rather they are located outside the main rivers either off stream or on minor tributary. The advantages of constructing on-channel dams include capacity to store large quantity of water, low cost construction, and ability to provide considerable flood control. There are also some negative points regarding on-channel dams. These points include relocation of people living around the area of dam, heavy engineering works like constructing spillways, and barrier to the fish passage. As for on-channel storage dams, there are also some positive and negative points for off-channel dams. The positive features of off-channel dams include no barrier to the fish passage and less number of engineering works. The negative features of off-channel dams include increased construction costs, seepage problems, and need of an extensive infrastructure for water circulation. 2.3.2 Spillway Spillways are constructed in order to contain excessive water quantity. They are located at some distance below the top of the dam. This hydraulic structure is used to control excessive water quantity in dams by providing water with a controlled escape in case of flooding. Spillways are basically used in emergency situations when the level of water in a dam reaches the top level causing the risk of flooding. Spillways let the extra water escape through the hole instead of causing the overflow situation. The hydraulic categories of spillways include open cut, shaft, side channel, siphon, tunnels, and shaft spillways (Khatsuria, 2005, p.5). Tunnels and open cut channels are two of the most famous spillway types. Tunnels generally have less capacity to contain water as compared to open cut channels. That is why open cut channels are more popular than tunnel shaped spillways. Gabion stepped spillway is the most common type of spillways used for dams (Chanson, 2002, p.12). The two main categories of spillways include controlled and uncontrolled spillways. Controlled spillways have built-in gates whereas in case of uncontrolled spillways, there are no gates and water is controlled through the spillway hole. 2.3.3 Outlet Works Dam outlet works generally consist of some bottom and spillways outlet works. Nalluri, et al., (2001, p.176) assert, “The design of bottom outlet works depends primarily on the purpose of the reservoir and the sediment inflow and deposition in the reservoir”. Engineers make use of dam outlets in order to manage extra water available in a dam. Outlet works consist of the tunnels that pass through a dam’s embankment. The function of these tunnels is to pass the water to the river downstream. The main functionality of dam outlet works and spillways is almost same. The dam outlet works are used to release extra water when the water present in the dam exceeds the normal capacity level. 2.3.4 Diversion Works Diversion work structures are developed in order to control the release of extra water from the dam and to eliminate the risk of flooding. Diversion works allow the necessary work to be carried out during construction without causing the flood risks (Gosschalk, 2002, p.117). At present, professionals from the field of civil engineering are making use of such structures that are able to resist erosive overtopping forces during different stages of dam construction. These structures are constructed in order to avoid the development of costly diversion structures. 2.3.5 Drop Structures Drop structures are developed by the engineers in order to pass water to lower elevation. These structures control the passing water’s velocity. They are small dams that are placed across the waterway. Drop structures provide engineers with the information about changes in gradient, velocity, and energy of water. Minimizing the falling flow effects is one of the primary objectives of the drop down structures. This objective is achieved through minimizing the air amount and degenerating energy from the flow of water. The two main properties, which are involved in the success of drop structures, include preventing outflanking and withstanding hydraulic pressure. There is no exact size of drop structures and the size varies from low wall structures to large dam structures. Drop structures are classified into three basic categories that include vertical, stepped, and slopped drop structures. Out of these three categories, vertical structures are the most widely used drop structures. The classification of drop structures is done by considering the downstream face shape at the center of water flow. In order to design a drop structure, hydraulic calculations and structural stability calculations are analyzed during the design phase of drop structures. 2.3.6 Stone Structures Stone is the most predominant building material in many existing ancient buildings. Stone is also used to construct various hydraulic structures like dams and spillways. Some of the most famous stone structures include gabion check dams, stone check dams, and masonry structures. Stone provides the dam structures with a lot of strength and stability. Stone structures have a very little chance of breaking or cracking. However, if a crack appears, there exist effective techniques to repair those cracks. 2.3.7 Conveyance and Control Structures The conveyance and control structures are used to transport the water to the public for irrigation purposes. This transportation involves canal structures that control and measure the flow of water. The canals keep the level of water stable while carrying it across various artificial obstacles and water bodies. The main structures for the conveyance and control of water include culverts and inverted siphons, super passage, pipe conduits, and siphon aqueducts. 2.3.8 Culverts and Measurement of Flow A culvert is cut through the hillside of the dam embankment in order to manage the flow of river water during the stages of construction. There is a concrete wall known as the fore bay that not only protects the inlet end of the culvert tunnel but also diverts the river water during different construction phases. Willis (2010) states the standard formula for the measurement of flow of water: Q = V · A    (quantity = velocity x area) Quantity (m3/s)   =   velocity of water (m/s)   x   cross-sectional area of water (m2) The measurement of flow of water is taken in cubic meters per second. Some basic culvert measurements include length of the culvert, width of the surface of water, radius of the culvert, and distance of water from culvert’s top to the surface of water. 3. Conclusion Summing it up, we can say that water is one of the necessities of life without which no species can survive. It is extremely important to construct dams on rivers in order to store a specific quantity of water. Storage dams, together with other hydraulic structures, are some of the most valuable and beneficial engineering works because they not only help in the development of a country’s economy but also play a vital role in eliminating the risk of floods. Some widely constructed hydraulic structures include storage dams, spillways, outlet works, diversion works, drop structures, stone structures, and culverts. Therefore, great importance should be given not only to the theoretical research regarding different hydraulic structures but also to the methods of analyzing and constructing them in order to get maximum benefits from these hydraulic structures. References Berga, L. Buil, J. Chonggang, S. & Jofre, C., 2003. RCC Dams – Roller Compacted Concrete Dams. Netherlands: Swets & Zeitlinger. Chanson, H., 2002. The Hydraulics of Stepped Chutes and Spillways. Steenwijk: Swets & Zeitlinger. Gosschalk, E., 2002. Reservoir Engineering: Guidelines for Practice. London: Thomas Telford Publishing. Jansen, R., 1988. Advanced Dam Engineering for Design, Construction, and Rehabilitation. New York: Van Nostrand Reinhold. Khatsuria, R., 2005. Hydraulics of Spillways and Energy Dissipaters. New York: Marcel Dekker. Nalluri, C. Novak, P. & Moffat, A., 2001. Hydraulic Structures. 3rd ed. New York: Spon Press. Tancev, L., 2005. Dams and Appurtenant Hydraulic Structures. London: Taylor & Francis. Willis, B 2010, Calculating the Flow of Water in a Culvert, viewed 20 July 2010, . APPENDIX A (A Spillway) APPENDIX B (Canal Drop Structure from Lee Lake) APPENDIX C (Bottom Outlet Culvert in a Dam) Read More