Some of these forces can be described by universal laws. The semigravity wall is a modification of the gravity wall in which small amounts of reinforcing steel are introduced. 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. Hydrostatic force force due to the pressure of a fluid at rest e. Gravity dam casei reservoir full case when reservoir is full, the major forces acting are weight of the dam, external water pressure, uplift. Seismic response of a concrete gravity dam considering.
If the gate is 4m wide measured perpendicular to the plane of the figure, determine the force acting on the lip. Chapter 2 gravity dam introduction forces acting on a gravity dam load combinations on the design of a gravity. Forces like temperature stresses and wind pressure have not been shown. The pressure due to water in the reservoir and that of the tailwater acting on. Forces acting on gravity dams 1 dam force free 30day. Seismic forces and stability analysis of gravity dam. Technically a concrete gravity dam derives its stability from the force of gravity of the materials in. Hydrogeological data five investigation boreholes have been drilled along the proposed axis of the dam to a depth rang ing between 15 and 31.
Rcc gravity dams, but also fill dams with a core or a concrete face, are generally analysed as twodimensional structures. Spillways,types and causes of failure design principle worksprincipal and shear stresses elementary profile of stress intensities stability analysis merits and demerits of 4. Gravity dam loads on concrete dams loads can be classified in terms of applicabilityrelative importance as primary loads, secondary loads, and exceptional loads. Forces acting on a gravity dam gravity dam computation of.
Failure of gravity dam occurs due to overturning, sliding, tension and compression. These forces are considered to act per unit length of the dam. A force is a push or pull acting upon an object as a result of its interaction with another object. Water pressurehydrostatic uplift pressure earthquake acceleration silt pressure wave pressure ice pressure self weight w counters the forces listed above. Problem 353 the forces acting on a 1m length of a dam are shown in fig. Seismic response of a concrete gravity dam considering hydrodynamic effects a. They can be constructed on any dam site, where a natural foundation enough to bear the weight of the dam. Although the weight of water varies slightly with temp. This type of structure is most durable, solid and required little maintenance. Unit weight of concrete 24 knm 3 and masonry 23 kn. Horizontal pressure by the water at the upstream and downstreamtail water. Computation of forces water pressure on the upstream face is the main destabilizing or overturning force acting on a gravity dam. The first version of a modern gravity dam was built between 1765 and 1800 in mexico.
Ppt gravity dam powerpoint presentation free to view. For good design, this intersection should occur within the middle third of the base. Changes to the hydrodynamics forces occur due to the water changing speed and direction. The shape of the arch may resemble a segment of a circle or an ellipse, and the arch may be curved in the vertical plane as well as the horizontal plane. Gravity walls the gravity wall figure 1a depends mostly on its own weight for stability. Unit mass of water is taken as kgm 3 and specific weight 10 knm 3 instead of 9.
How is hydrostatic force on the vertical or inclined planes determined. The principle force acting on a dam is the weight of the water behind the dam. Gravity dams gravity dams criteria for selection of dam site, construction material, forces acting on gravity dam, modes of failure, stability analysis, safety criteria, methods of design, stress analysis and stress contours, galleries, instrumentation, joints, keys, water seals, temperature control in concrete dams, foundation treatment. The resultant of all these downward forces will represent the total weight of the dam acting at the center of gravity of the dam. 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. Forces can be classified as external wind, gravity or internal. It is usually made of plain concrete and is used for walls up to approximately 10 ft in height.
Curved gravity plan a gravity dam that is curved in plan. Further details on temperature control methods are provided in chapter 6. For the force components in the xdirection, we may write note that is the vertical elevation difference between the two points. Stability analysis steps for analysis of gravity dam referances introduction what is a dam. A gravity dam can be combined with an arch dam into an arch gravity dam for areas with massive amounts of water flow but less material available for a purely gravity dam. This cross section eventually evolved into the common triangular cross section design of todays gravity dams. The crosssection can then be divided into rectangles and triangles. It is called dynamic because these forces change their magnitude, direction, and point and plane of application over time. Seepage, in soil engineering, movement of water in soils, often a critical problem in building foundations. Pdf comparison of design and analysis of concrete gravity dam.
Uplift occurs when water on the headwater side of the dam enters pores and fissures in the foundation at the base, as well as pores in the dam itself. Shear strength of damfoundations rock interface a case. The magnitude of forces, their direction, and their point and plane of application influence how they affect. Pdf seismic response of concrete gravity dam researchgate. Determination of various forces which acts on the structure is the first step in the design of dams. Ppt gravity dam powerpoint presentation free to view id. Dec 14, 2016 discussion on the calculation of forces acting on concrete gravity dam concrete dam engineering 48 for further reading. Different types of forces acts on a dam structure such as water pressure, self weight, wave pressure etc. Bhakra dam is the highest concrete gravity dam in asia and second highest in the world. For example, gravity forces can be calculated using newtons law of gravitation. Forces acting on gravity dams 1 dam force free 30day trial.
Forces acting on components such as stilling basins, spillway faces, bridge piers, culvert valves, spillway gates, lock guard walls, floodwalls, etc. Weight of the dam per unit length is equal to the product of the area of crosssection of the dam and the specific weight or unit weight of the material. Hydrody namic forces result from water changing speed and direction as it flows over a spillway. Calculating forces on components of hydraulic structures. Gravity dams may be classified by plan as straight gravity dams and curved gravity dams, depending up. Adi forces acting on gravity dam ce in hindi youtube. Determine the horizontal and vertical components of the hydrostatic force against the dam and the point cp where the resultant strikes the dam. Design and construction of concrete gravity dams nptel. The dam must be strong and sturdy and have strong connections to the ground, in the form of foundations, to help it stand. Forces acting on gravity dam weight of the dam, w in a gravity dam the weight of the structure is the main stabilizing force, and hence the construction material should be as heavy as possible. The design of rcc gravity dams is similar to conven. Later gravity dams used a trapezoidal cross section.
The three main forces acting on a gravity dam are the thrust of the water stored. Pdf experimental and numerical investigation of dam. Pressure acts through the center of gravity of the water column resting on the sloping upstream face. A detailed sketch of a gravity dam is shown in fig. Technically a concrete gravity dam derives its stability from the force of gravity of.
Stress is defined as the force acting on an area, see equation 2. When analyzing forces in a structure or machine, it is conventional to classify forces as external forces. Failure of gravity dams causes and its failure modes. The uplift is assumed to be the reservoir pressure from the us face to the end of the crack and from there to varying linearly to the tail water pressure at the ds. Other forces include the weight of the dam itself and in some cases wave pressure and earthquake forces. External forces arise from interaction between the system of interest and its surroundings. That means that only the stability of thin 2d crossslices is investigated. The weight of each along with their centers of gravity can be determined. Gravity dam design challenge challenge scenario ds. Problem 266 determine the resultant of the three forces acting on the dam shown in fig.
Dam with water at its full reservoir level is subjected forces due to iwater pressure. Structural stability and 2d finite element analysis of. Tech civil engineering final year last semester numerical on gravity dam video link. The foundation surface for each slice is implicitly assumed to be horizontal in the direction of the dam axis, that is crossvalley. The inward compression of the dam by the water reduces the lateral horizontal force acting on the dam. A gravity dam is a dam constructed from concrete or stone masonry and designed to hold back water by primarily using the weight of the material alone to resist the horizontal pressure of water pushing against it. External forces, constraint forces and internal forces. The forces that come in this category are weight of the dam, weight of water acting on inclined faces of the dam, uplift pressure etc. Forces acting on a gravity dams with diagram geography. The forces acting on an overflow dam or spillway section are complicated by steady state hydrodynamic effects. To prevent water pressure from pushing gate ab open, a small extension, or lip, is provided at a. The upward ground reaction varies uniformly from an intensity of p 1 knm to p 2 knm at b. Gravity dams are constructed from masonry or concrete.
The forces acting on a gravity dam spillway section are complicated by the hydrodynamic effects of the flow. Apr 30, 2016 this is the topic for students pursuing b. By researching the size and direction of all the forces acting on a dam, engineers design a structure that is able to resist all these forces. Up lift on a dam is critical to account for as it is the second largest force acting on the dam. Previously in this lesson, a variety of force types were placed into two broad category headings on the basis of whether the force resulted from the contact or noncontact of the two interacting objects. Forces acting on a dam structure and calculations the constructor. Gravity dams arch dams buttress dams 3 based on usage of dam. Gravity dams may be classified by plan as straight gravity dams and curved gravity dams. Scribd is the worlds largest social reading and publishing site. Such dams are usually constructed of a series of vertical. The resistance to sliding is a function of the cohesion c inherent in the. A gated spillway monolith of a concrete gravity dam is shown in fig.
Generally, the dynamic analysis of gravity dams is a difficult and complicated process, as it is influenced by two important factors. The reservoir water forces acting on an arch dam are carried laterally into the abutments. Forces acting on gravity dams 1 free download as word doc. The magnitude of dead load is considered equal to the weight of concrete plus appurtenances such as gates and bridges. An example design of small african journals online. The overturning stability is calculated by calculating the all vertical force and the horizontal force acting on the gravity dam. Design of gravity dam, calculation in reservoir full. Hydrostatic force force due to the pressure of a fluid.
All the predominant forces that act on the dam have been shown in the figure itself. Pdf design of gravity dam table of contents theogene. Seepage depends on several factors, including permeability of the soil and the pressure gradient, essentially the combination of forces acting on water through gravity and other factors. Problem 266 resultant of nonconcurrent force system. Gravity dams gravity dams criteria for selection of dam site, construction material, forces acting on gravity dam, modes of failure, stability analysis, safety criteria, methods of design, stress analysis and stress contours, galleries, instrumentation, joints, keys, water seals, temperature control in concrete dams, foundation. Gravity dams may be classified by plan as straight gravity dams and curved gravity. Gravity dam is so proportioned that its own weight resists the forces acting upon it. Determine p1 and p2 and also the horizontal resistance to sliding. Gravity dams are designed so that each section of the dam is stable and independent of any other dam section.
The dynamic load is the forces that move or change while acting on the structure. In the design of a dam, the first step is the determination of various forces which acts on the structure and study their nature. Concrete gravity dams usually run in a straight line across a broad valley and resist the horizontal thrust of the retained water entirely by their own weight. Forces acting on a solid gravity dam one of the primary design requirements in case of concrete or masonry gravity dam built on rock foundation is to ensure adequate factor of safety for shear and sliding failure at the dam foundation interface. Basic conditions for a plane surface submerged in a fluid force on the surface.
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