For this type of dam, it is essential to have an impervious foundation with high bearing strength. Treatment of soft or weak foundation in a rockfill dam is of importance due to being susceptible to the large settlements, which may cause the dam body subjected to undesirable deformations and even, catastrophic failures. Foundation treatment in dams dam fault geology scribd. Foundation treatment and construction of concrete dams can be discussed in three phases.
Dam foundation treatment for arupuni dam term paper presentation at iit delhi. 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. Curved gravity dams designed for arch action and other types of concrete gravity dams are not covered in this manual. The foundation excavation was designed to remove rock mass with open and clay infilled defects due to nearsurface stress relief, to provide a kinematically stable foundation with suitable rock mass strength, stiffness and permeability characteristics on which to construct an 87m high concrete gravity dam and the two saddle dams. Dams, dam foundations, and reservoir sites 1st edition. Grouting, drainage, and excavation of cutoff drifts and backfilling them with concrete. Design of sand and gravel foundation for dams exposed. In order to measure permeability of dam foundation area, lugeon test shall be conducted. However, the design of the foundation does not end with the final design drawings for the project. A gravity dam is designed in such a way that it resists all external forces acting on the. Grouting, remedies against piping and exit gradient 4.
Embankment dams can be constructed even on the alluvial deposit and pervious foundations. This method considers the damreservoirfoundation rock interaction by taking the foundation rock flexibility effects, compressibility of the impounded water and the absorptive effect of the reservoir bottom materials into consideration. Lulugeon value is water volume injected at 10kgfcm2 for 10 minutes per meter. The drainage hole pattern will relieve the water that may seep through the massive sandstone. 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. Verifying the ground treatment as proposed by the secondary permeability index during dam foundation grouting. Foundation preparation for gravity dams foundation treatment against sliding the following measures are usually taken to improve the sliding resistance of dam foundation roughening of base.
To prevent sliding the contact with the foundation and the foundation itself must have appreciable shear strength. Gravity dam design united states army corps of engineers. Further treatment of hydrodynamic effects is given in reference 3. Dl51081999 design specification for concrete gravity dam.
Design criteria for co arch and gr vity dams united states department of the interior. Check dam is a small dam designed to reduce flow velocity and control soil erosion diversion dam is a type of dam that diverts all or a portion of the flow of a river from its natural course masonry dam is a type of dam constructed with masonry. Pdf the design of foundation treatment measures for dams. Foundation preparation for rcc dams founded on difficult foundation conditions by paul c. Pdf the design of foundation treatment measures for dams on. In addition to the above foundation treatment for the dam, radial grouting was provided for in the spillway tunnels and around the diversion tunnel plugs, and. Height is the vertical dimension from the downstream toe of the dam at its lowest point to the top of the dam. Foundation treatment in dams free download as powerpoint presentation.
Purchase dams, dam foundations, and reservoir sites 1st edition. Conventional concrete and roller compacted concrete are both addressed. The method of treatment may differ for foundation, dams with upstream membrane, dams with impervious core and homogeneous dams. Safety, middle third rule, elementary profile of a dam 4. Engineering geology considerations for specifying dam foundation objectives william a. The analysis of the concrete gravity dams foundation. The presence of a pervious granular and compressible foundation loose sand required special techniques to reduce seepage through foundation, and to avoid cracking of the till core caused by differential settlement of the foundation bentonite cap.
The 107 m high earth dam, commissioned in 1975, is built on a 126 m of alluvial deposits. Rcc dams, normally designed as traditional gravity structures similar to conventional concrete dams, require treatment of the foundation rock in accordance with generally accepted practices developed and improved by the profession over the last 50 years or so. General considerations, crosssectional profiles, strength, stability and safety factors against overturning. The seepage safety evaluation of a concrete gravity dam is the main task of dam security monitoring. Shear strength of damfoundations rock interface a case. Concrete dam construction and foundation treatment. The weight of a gravity dam and the width of its base prevents it from being overturned when subjected to the thrust of impounded water kennard, 1995. It is made watertight by pointing the joints with cement. The main objective of treatment is to restore the water tightness of the dam and foundation. Rigorous conditions are not required for the dam foundation, while hard and sound rock foundation is necessary for concrete dams.
Foundation treatment of embankment dams with combination of consolidation and compaction groutings fardin jafarzadeh sharif university of technology, iran. Missouri university of science and technology scholars mine. For structures consisting of a section of concrete gravity dam within an embankment dam, the concrete section will be designed in accordance with this manual. A curtain grout holes b blanket grout holes c special purpose, offpattern grout holes d drain holes. Be cause of the increasing reservoir area as height is added, large. Grouting at tannur dam in ejge hashemite university. Pdf well planned foundation treatment measures for dams constructed on karst foundations are essential. Effect of foundationreservoir interaction on seismic. During construction foundation conditions need to be evaluated as excavation and construction proceeds to determine if foundation conditions are. Bulging of dam crest east of spillway observed at austin bayless dam in january 1910. The dam foundation had got also several pot holes, one of which was nearly 10m deep having a circular cross section of 1.
All these foundation treatment undertaken at the dam site increased the. It includes a 250 m high rcc gravity dam which is the worlds highest of its kind. Foundation treatment for grand coulee forebay dam in washington. 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. Gravity dams are well suited for blocking rivers in wide valleys or narrow gorge ways. To be effective, these measures must be tailored to the specific problems of the individual dam. Dam foundation grouting at gibe iii dam studio pietrangeli. Grout system stage pressure bar time duration of each step pilotcontrol hole other hole 1st 1 9. Shear resistance on an existing joint in rock foundation of a gravity dam 4. In carrying out stability calculations for any proposed section of a dam, the uplift must be taken into account. Causes of failure of earthen dams and suggested remedial. Stability of the dam foundation and other geologic.
Design of gravity dam, calculation in reservoir full. Whenever the foundation is sloping steeply and shear zones, faults and other weak layers exist in the foundation, necessary treatment of the foundation should be carried out before laying the concrete. The dam subjected mce excitation experiences serious cracks at heel and toe of the dam. This consumed huge quantity of cement to plug this by concrete. Case studies of foundation grouting using the gin method. Concrete gravity dam with double grout curtain and c holes intersecting a. Gravity dam is constructed of concrete andor masonry andor laidup stone that relies upon its weight for stability. Key words seismic response, gravity dam, damfoundation interaction, hydrodynamic effect, numerical analysis, case study. Dam foundation treatment free download as powerpoint presentation.
The foundation treatment for an exposed pervious foundation of shallow depth a cutoff trench excavated to the impervious stratum, called a positive cutoff, should always be used because it is the most positive means of avoiding excessive seepage losses and. Failure of gravity dams causes and its failure modes. Well planned foundation treatment measures for dams constructed on karst foundations are essential. In the last half century, hq has built almost 500 dams and dykes in various soil and rock foundation and throughout the time, it has got valuable. Chapter v geotechnical investigations and studies dams, dam sites, or appurtenant structures 51 general an adequate assessment of site geologic and geotechnical conditions is one of the most important aspects of a dam safety evaluation. The specific treatment consisted in a high pressure washing of the drilled holes to eliminate. The cutoff drifts and the grouting will seal the cracks and joints. To be effective, these measures must be tailored to the specific problems of the individual dam site. When situated on a suitable site, a gravity dam can prove to be a better alternative to other types of dams. Foundation preparation for rcc dams founded on difficult. Force acting on gravity dams factors in site selection general design consideration procedure to build a dam foundation investigations foundation treatment mode of failure and criteria for structural stability. Understanding the foundation and the required treatment is critical to developing the final dam design. A gravity dam depends on its own weight for stability and is usually straight in plan although sometimes slightly curved. Only the repair work which is simple, straight forward and within the limits of human capabilities is carried out.
Evaluation of the safety of either a new or an existing dam requires. Concrete dams, especially gravity structures, lend themselves favorably to this concep. Today, as in the past, the earthfill dam continues to be the most common type of dam, principally because its construction involves using. Failure of gravity dam occurs due to overturning, sliding, tension and compression. As they rely on their own weight, it is necessary to construct them on a solid foundation of bedrocks. For a gravity dam of 100 m, the foundation uplift pressure is approximately 20% of the dam weight under normal reservoir level and is therefore the main load for concrete gravity dams which directly influences the dam stability 10, 11.
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 damfoundation interface. The uplift pressures caused layers of the foundation rock to slide on each other, resulting in the bulge and ultimately the failure of the dam photo source. The foundation treatment of glen canyon dam consists of three parts. At the kavar dam, an unusual combination of a surface membrane. Some cross sections of dams with rock foundations showing locations of drilled holes for foundation treatment. Measured and computed uplift pressures for shasta dam. Dental treatment for faults in foundation of gravity dam zuo dongqi, shen jiayin, zhang yang east china technical university of water resources synopsis the stress analysis for the gravity dam is presented by means of our program epbfm employing a coupling fem and bem technique for. The drainage hole pattern will relieve the water that may. Treatment of soft or weak foundation in a rockfill dam is of importance due to being susceptible to the large settlements, which may cause the dam body subjected to undesirable deformations and. The target lu value after foundation treatment is generally 3 to 5. The most reputed and wellknown case is the cutoff walls of manic 3 main dam built in 197172 this project is followed in the 80s and 90s with the development of the. Shear zone treatment at dam foundation level science. Since gravity dams must rely on their own weight to hold back water, it is necessary that they are built on a solid foundation of bedrock.
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