Module 2 principles and sizing of a gravity fed pipeline. If the height of the dam to be constructed is more than that hlim, the dam is known as high gravity dam. Dam design and construction, reservoirs and balancing lakes. Forces acting on a gravity dams with diagram geography. Gravity dams are also usually cheaper than earth dams if suitable soils are not available for the construction of earth dams. A gravity dam is mostly straight in plan and is known as straight gravity dams however, it may also be slightly curved. Pdf design of gravity dam by genetic algorithms researchgate. Spillway crest profile kokpinar dam carried out extensive experiments to investigate the hydraulic performance of a ramp. Hydraulic characteristics of energy dissipation of hydrau licjump type stilling. Practical profile of a gravity dam civilengineering subject. By using concrete, the weight of the dam is actually able to resist the horizontal thrust of water pushing against it.
However, nowadays with improved methods of construction, quality control and curing, concrete is most commonly used for the construction of gravity dams. Therefore, the suitable base width will be equal to b28. Gravity dams may be classified by plan as straight gravity dams and curved gravity. The results show that the practical profile of gravity dam is safe up to earthquake. A gravity dam has been defined as a structure which is designed in such a way that its own weight resists. The advantage of gravity dam is that its structure is most durable and solid and requires very less maintenance. An arch dam that is curved both vertically and horizontally. It is, in addition, necessary that dams be frequently inspected. Based on the structural types adopted, dams can be divided into gravity dams, arch dams, buttress dams, and others. Some free board is essential whereas elementary profile does not provide any free board. V 1 6 x b 0 b b 6 pmax 2 w b and, pmin 0 hence, the maximum vertical stress equal to 2 w w will act at the heel and the vertical stress at toe will be zero. Part of the energy of the water is used by the head losses. These dams are most permanent ones, requires little maintenance and is most commonly used. Sefidroud dam is located in a giulan province, iran.
Although theamount of cement required is largerthan in the previous methods,itscost is more thanoffset. Draw the elementary profile of gravity dam and explain the. Types of dams, factors affecting selection of type of dam, factors governing selection of site for a dam. State of art design and analysis of concrete gravity dams. If a gravity dam is subject to horizontal pressure due to water along with its own weight, the elementary profile of the dam would be a right angled.
The vertical, principal and shear stresses are also obtained. A gravity fed system function thanks to the gravity. A gravity dam is generally straight in plan and, therefore, it is also called straight gravity dam. This type of a structure is most durable and solid and requires very less maintenance. Design of gravity dams it is not possible to adopt elementary profile as such, because of certain practical requirements. App to calculate various forces acting on a gravity dam. Therefore the dam is subjected to horizontal water pressure at the upstream face and uplift pressure at the base. While determining the elementary profile of a gravity dam only pressure due to water is considered. Experiences at spaulding dams three separate concrete dams form pacific gas and electric co. Forces acting on a gravity dam, causes of failure of a gravity dam, elementary profile and practical profile of a gravity dam, limiting height of a low gravity dam, factors of safety stability analysis. Further details on temperature control methods are provided in chapter 6. An elementary profile is only theoretical profile which needs to. A gravity dam has been defined as a structure which is designed in such a way that its own weight resists the external forces. Practical profile of a gravity dam civilengineering subject tutorial.
The elementary profile of a gravity dam is a triangular section having. Design of gravity dam, calculation in reservoir full. Dams of earthfill or rockfill materials are generally called embankment dams. A gravity dam is an essentially solid concrete structure that resists imposed forces principally by its own weight. Gravity dam diagram figure 3 typical gravity dam views showing common terms. Gravity is a force which attracts all objects on the earth surface, due to the attraction exerted by the planets mass.
Design of gravity dam numerical stability check of. Seismic forces and stability analysis of gravity dam. Zeidan state of art in design and analysis of concrete gravity dams 2014 6 figure 1. Same shape as hydrostatic pressure distribution diagram 3. Stable channel hydrology and geology topography, geology, sociology.
Forces acting on a gravity dam, causes of failure of a gravity dam, elementary profile and practical profile of a gravity dam, limiting height of a low gravity dam, factors of safety stability analysis, foundation for a gravity dam, drainage and inspection galleries. Elementary profile of stress intensities stability analysis merits and demerits of 4. It can build any high wheres the high of an earth dam. Gravity dams may be classified by plan as straight gravity dams and curved gravity dams, depending up on the axis alignment. Pdf design and construction of gravity dams dian eka.
The elementary profile is hypothetical because an actual gravity dam has some minimum top width and free board, and it will also be subjected to forces other than. It is the most important force, particularly for gravity dams. Therefore, it results in higher forced aeration as compared with no ramp case. Elementary profile of a dam subjected only to external water pressure on upstream side, will be right angled triangle, having zero width at water level and a base width b at bottom, i.
Curved gravity plan a gravity dam that is curved in plan. The design of rcc gravity dams is similar to conven. The elementary profile of a dam, subjected only to the external water pressure on the upstream side, will be rightangled triangle, having zero width at the water level and a base width b at bottom, i. Therefore the dam is subjected to horizontal water pressure at the upstream face and uplift pressure at. If the density of concrete is 2400 kgm 3 and that of water is kgm 3, determine the maximum compressive stress at section mn if the depth of the water behind the dam is h 15 m. A gravity dam requires the least maintenance of other dams.
Concrete gravity dams are designed so that the weight of the dam itself the. A gravity dam may be constructed either of masonry or of concrete. For such a dam, the section will have to be given extra slopes to the upstream and downstream sides, below the limiting height, to bring the compressive stress within the permissible limits, as illustrated in fig. The basic shape of a concrete gravity dam istriangular in section figure 49a, with the top crest often widened to provide a roadway 2. In this lesson we will learn how to fix an elementary profile of a gravity dam. In order to size a gravity fed system, it is important and necessary that a technician knows and understands how gravity fed systems work. Some modifications have to be incorporated, to make it adaptable in practice. Plan view of the nwamitwa dam right bank tongue wall the crosssection profile of the tongue wall gradually changes from a wide section like that of the noc. No any other force except forces due to water such as weight of dam, water pressure and uplift pressure 2. It is the resting force that resists all the external forces acting upon the dam. Construction, advantages, and disadvantage define gravity dam.
This type of a structure is most durable and solid, and requires very little maintenance. They are designed to hold back large volumes of water. Theoryofdesignofarchdnns 30 athetheoreticalarch 51 btheeconomicradius 31 2. A gravity dam is a dam constructed from concrete or stone masonry and designed to hold back water by using only the weight of the material and its resistance against the foundation to oppose the horizontal pressure of water pushing against it. A gravity dam is a solid structure, made of concrete or. Gravity dams are relatively more strong and stable as compared to earth dams. What do you mean by the elementary profile of a gravity. Previous ferc gravity dam guidance dealt with nappe forces by ignoring the. What do you mean by the elementary profile of a gravity dam dhs. Supervision of construction or reconstruction of the dam by a licensed professional engineer is required to insure that the dam will be built according to the approved plans. In an upcoming post, we will see the design analysis of gravity dam, where we can use the abovementioned formula in detail. Failure of gravity dam occurs due to overturning, sliding, tension and compression. Three main forces acting on the elementary profile of a gravity dam are i self weight of the dam weight of dam w 12. This limiting height draws a dividing line between a low gravity dam and a high gravity dam.
The principal stress for an elementary profile is given by eqn i. Elementary profile of a gravity dam civilengineering subject tutorial. Pdf multiple step method of design of gravity dam and. Modifications in elementary profile are necessitated due to following reasons. An elementary profile is only theoretical profile which needs to be modified for dependency in actual practice. For structures consisting of a section of concrete gravity dam within an. Gravity dams are constructed from masonry or concrete. Introduction types of dams characteristics of dams reservoir planning 7.
Forces acting on gravity dam typical loads civil planets. Practical profile of a gravity dam we have already seen that the elementary profile of a gravity dam is triangular in shape, having. Design of flood control gravity dam in wadi banban,riyadh. A profile is a developed elevation of the intersection of a dam with the original groundsurface, rock surface, or excavation surface along the axis of the dam, the. Gravity dams are designed so that each section of the dam is stable and independent of any other dam. A gravity dam is designed in such a way that it resists all external forces acting on the dam like water pressure, wind pressure, wave pressure, ice pressure, uplift pressure by its own selfweight. The increasing width of the section towards the base is logical since the water pressure also increases linearly with depth as shown in figure 48a.
A gravity dam is defined as a solid structure, made of concrete or masonry, constructed across a river to create a reservoir on its upstream the section of the gravity dam is approximately triangular in shape with its apex at its top and the maximum width at the bottom. In the study, a concrete gravity dam with the height of 200 m is selected and finite element models of the dam are constituted including five different lh ratios such as 0. Gravity dams are designed so that each section of the dam is stable and independent of any other dam section. A gravity dam built up of boxes, crossed timbers or gabions, filled with earth or rock. A low gravity dam is the one in which the height h is less than hlim so that maximum compressive stress is not greater than the allowable stress. The tongue wall is a concrete gravity structure that transitions from the concrete gravity spillway section to the earthen embankment section as can be seen in figure 2. Gravity dam y910026 free download as powerpoint presentation. A map and description of thesezones is available in physical and engineering. Difference between practical profile and elementary. The preliminary design of gravity dams is done by two dimensional gravity method by considering the dam as being made of a number of cantilevers of unit length and acting independently of adjacent cantilevers. A gravity dam is a structure so proportioned that its own weight resists the forces exerted upon it. Water resources engineering ii wre ii notes pdf sw.
The total volume of output discharge from the dam is estimated as 6000 m 3 s. A developed elevation of the intersection of a dam with the original ground. In order for a dam to safely fulfill its intended function, the dam must also be constructed, operated and maintained properly. Asically, gravity dams are solid concrete structures that. A dam built to divert water from a waterway or stream into a different watercourse. If the density of concrete is 2400 kgm 3 and that of water is kgm 3, determine the maximum compressive stress at section mn if the depth of the water behind the dam. Its experimental findings indicated that use of a ramp increases the shear length l j and free surface aeration of the water jet. In this module, a first section chapter ii is devoted to the functioning of gravity fed system, giving definitions of concept such as gravity, pressure and head loss. Design of gravity dam numerical stability check of gravity. Failure of gravity dams causes and its failure modes. Sl3192005 design standard for concrete gravity dams. A concrete gravity dam is a massive concrete structure, roughly triangular in shape, and designed so that its weight ensures structural stability against the hydrostatic pressure of the impounded water and other forces that may act on the dam.
What do you mean by the elementary profile of a gravity dam. Gravity dams modification 2 definitions 3 3 hazard classification 5 4 design and construction documents 5 5 hydrologic criteria 7 6 hydraulics of spillways 10 6a flashboard policy 12 7 outlet works and conduits 15 8 geotechnical investigations 16 9 earth dams 18 10 structural stability criteria for 21 11 existing dams. Very often dams are constructed with a combination of two or more structural forms or materials. Based on structure and design, dams can be classified as follows. Practical profile of a gravity dam civilengineering. Gravity dams are particularly suited across gorges with very steep side slopes where earth dams might slip. Gravity dam does no trial suddenly, it gives enough warning time whereas earth dams generally fail suddenly. Where good foundations are available, gravity dams can be built upto any height. Jan 28, 2014 gravity dams a gravity dam has been defined as a structure which is designed in such a way that its own weight resist the external forces. Problem 911 a concrete dam has the profile shown in figure p911. The dam is buttress gravitydam with a wall height of 106 m, crest length of 425 m, crest width of 8 m, and reservoir volume of 1198 million m 3.
1074 1010 1666 1558 1582 827 616 1598 1884 155 434 1948 1132 1477 714 234 423 1113 1056 1228 798 1642 1861 228 264 1088 1636 1241 1242 1297 619 1114 1704 1617 832 1816 106 319 1440