Gravity dams are massive structure dam which is constructed of concrete or stone masonry. Like most of engineering structures, earth dams may fail due to various reasons such as faulty design, improper construction and poor maintenance practices, etc. All the steps that the methodology comprises have been developed exhaustively, achieving different estimates of the target conditional probability of failure. The failure can occur either in the interface between dam and foundation or in the foundation itself. Table of dam failures university of california, davis. Three scenarios are considered normal water condition, c ritical water condition and an earthquake hitting the normal water scenario. Height is the vertical dimension from the downstream toe of the dam at its lowest point to the top of the dam. Concrete dam analysis arch, gravity and buttress dams chapter 5, concrete dams 3 2014 draft risk analysis does not reverse the burden of proof with respect to the failure of the dam. The development of excessive uplift pressures creating tension at the heel of the dam and downstream scour due to overtopping likely.
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. Conventional concrete and roller compacted concrete are both addressed. Uplift along failure planes within the b ody of the dam shall be assumed to vary from 100% of normal headwater at the upstream face to 100% of tailwater or zero, as the. This manual applies to all hqusace elements, major subordinate commands. Sliding along the base of the dam is probably considered the most prevailing mode of failure for gravity dams ghanaat, 2004. Erosion of soil near to the foundation causing settlement. Any stability analysis of the dam should seek to apply forces that are compatible with the failure mechanism being assumed.
There have been a total of 45 dam failures in california. A hollow gravity dam is a dam constructed of concrete andor masonry on the outside but having a hollow interior relying on its weight for stability. Causes of failures of earthfill dams the constructor. The failure under this category may be due to overtopping, wave erosion, top erosion and gullying. About 40% of earth dams failure have been attributed to hydraulic failure. A buttress dam is a specific type of gravity dam in which the large mass of concrete is reduced, and the forces are diverted to the dam foundation through vertical or sloping buttresses. Gravity dam is constructed of concrete andor masonry andor laidup stone that relies upon its weight for stability. Pdf dams have been constructed for millennia, influencing the lives of humans and the ecosystems they inhabit. A crib dam is a gravity dam built up of boxes, crossed timbers, or gabions filled with earth or rock.
Special emphasis is given to dam breach analysis within the context of the risk assessment process used by the bureau of reclamation reclamation. The purpose of this manual is to provide technical criteria and guidance for the planning and design of concrete gravity dams for civil works projects. The main objective is to obtain the relationships between factors of safety and the probability of failure against sliding for a given damreservoir system. The failure flow is usually substantially less than flood failure flow as reservoir level and volume are lower and there is no incoming flow. The major causes of failures of gravity dam structures are. Earth dams can also experience seepage and structural failure caused by poor engineering and planning. The federal emergency management agency fema has developed. A gravity dam depends on its own weight for stability and is usually straight in plan although sometimes slightly curved. Concrete dam engineering 1 0401544 hydraulic structures university of sharjah dept. Tips for selection of materials for high strength concrete pdf. Design of gravity dam, calculation in reservoir full. The relevant yearly probability of failure seems to be in average between 104 and 105 but varies considerably and is difficult to assess for each dam. This dam is an earth filled dam capable of holding 36,500 acre feet. Concrete dams case histories of failures and nonfailures with.
The self weight of the gravity dam acts through the centre of gravity of the. Failure of a dam can be categorized into three different failure modes. Stability evaluation of gravity concrete structures dams, retaining walls. A smeared crack model for seismic failure analysis of.
By definition, a gravity dam is one where that depends upon the force of gravity to prevent it from being pushed aside by the water it contains. Gravity dams are constructed from masonry or concrete. Slide failure at dam association of state dam safety officials asdso. That study listed and discussed dam failures that have occurred over the past 900 years. If you have some, be sure to pay your homeowners insurance. Modes of dam failure and monitoring and measuring techniques. Of these, the most comprehensive is the 1983 volume by jansen 1 published by the u. 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.
On upstream face pressure exerted by water is stored upto the full reservoir level. Pdf sliding and overturning safety factors of concrete gravity. Tigra dam failure, gwalior, india a case of sedimentary. Civil engineering failures engineering and technology.
The various causes leading to the failure of earth dams can be grouped into three categories i. Between the years 2000 and 2009 more than 200 notable dam failures happened worldwide. Modes of dam failure and monitoring and measuring techniques vii. Repeated overtopping can eventually result in a catastrophic collapse of the dam. Quantitative failure metric for gravity dams hariri. Gravity dams are designed so that each section of the. As consequences of dam failure are devastating, the failure modes and seepage of the dam needs to be analyzed. Like most of engineering structures, earth dams may fail due to. Dam failure chapter 5 2019 utah state hazard mitigation plan page 2 a buttress dam is a specific type of gravity dam in which the large mass of concrete is reduced, and the forces are diverted to the dam foundation. Chapter 6 concrete dam engineering with examples 1. An advanced threeparameter yield criterion is utilized in finite element formulation.
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. Dam safety based on risk analysis methodologies demand quantification of the risk of the damreservoir system. Hydraulic failure, seepage failure and structural failure. Gravity dam modes of failure and criteria for structural stability of gravity dams a gravity dam may fail in the following ways. There have been several studies of dam failures published in the last 30 years. An experimental study of failure of a gravity dam on a. In addi tion, the potential for failure planes in the rock below the dam must be considered. In september 1965 a serious piping failure occurred on the right abutment, with reservoir water percolating along valleyside sheet joints in the sandstone with only 46 feet of head. 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. Failure of gravity dams causes and its failure modes. Touileb and others published gravity dam probability of sliding failure with overtopping and conditional drainage. In the case of gravity dams on rock founda tions, a failure plane shall be assumed between the dam and the foundation. The dam was loaded by fluid pressure on the upstream face and upward forces simulating the uplift pressure. A gravity dam may fail by the failure of its material, i.
The prevailing mode of failure for gravity dams is probably sliding along the base of the dam or along planes of weakness within the foundation. Gravity dams are constructed of vertical blocks of concrete with flexible seals in the joints between the blocks. Since the failure of the dam was mostly caused by the subterranean rock, the only. Pdf multiple step method of design of gravity dam and. However, the ultimate cause of failure is generally agreed to be the result of sliding of sections of the gravity dam along the untreated, stratified foundation. This is conducted by determining the limit states and seepage of the dam.
Examples stacked wood walls its everyones favorite way to go, much less expensive than other support systems. The methodology proposed has been fully applied to a concrete gravity dam and for the sliding along in the damfoundation contact plane failure mode. Another type of dams are the gravity dams which are constructed from concrete and masonry. Past dam failure disasters showed that the loss of life in the event of a dam failure is directly related to the warning time available to evacuate the population at risk downstream of the dam. Other dams have failed due to specific shortcomings in the dam itself or an inadequate assessment of the.
A dam failure or dam burst is a catastrophic type of failure characterized by the sudden, rapid, and uncontrolled release of impounded water or the likelihood of such an uncontrolled release. Earth and rock fill dams are widely used throughout the world, and most of the dam failures involve such. Methodology for estimating the probability of failure by. It is not up to the ferc to prove that failure in a given situation is certain, rather it is up. Dam awareness may 2018 introduction responsibility and. This means that, for a given initial state of the system, and for the several failure modes considered, it is necessary to estimate the probability of the load events and the conditional probability of response of the system for a given load event, as well as estimating the. Design and construction of concrete gravity dams nptel. Gravity dam design united states army corps of engineers. Chapter iii gravity dams 30 contents title page 31 purpose and scope 31 31. Any malfunction or abnormality outside the design assumptions and parameters that adversely affect a dams primary function of impounding water is considered a dam failure. Learning outcome after this lecture, students should be able to 1. Failures have occurred for a variety of reasons, the most common failure being overtopping.
Many dams have failed where the sliding hazard was ignored or given inadequate attention. Stability evaluation of gravity concrete structures. Dams it is important for a gravity or buttress dam to maintain its structural integrity and remain stable against sliding. Kianoush, fembased parametric analysis of a typical gravity dam considering input excitation. Dams are owned and operated by many different types of. In order to study this question, the analysis of probability of failure of a gravity dam for the sliding failure mode has been performed in this thesis according to the theme c in. Multiple step method of design of gravity dam and comparison with cadam software conference paper pdf available september 2016 with 6,557 reads how we measure reads. Ferc engineering guidelines riskinformed decision making. Before a gravity dam can overturn physically, there may be other types of failures, such as cracking of the upstream material due to tension, increase in uplift. Causes of failure of earthen dams and suggested remedial.
Different causes of failure of earthfill dams are explained below. It is determined that the proposed damage indices can indeed provide a quantitative metric for the degree of failure in gravity dams in terms of the input dynamic motion. Stability analysis of nonoverflow section of concrete. Abstract concrete gravity dams make up about ten percent of the more than 85,000 dams that. Curved gravity dams designed for arch action and other types of concrete gravity dams are not covered in this manual. If it is possible to monitor or measure the hazards that may impact on any particular.
The effect of reservoir water is considered for calculation of. Francis failure, but relatively litte attention has been paid to the austin dam. City of oxnard hazards dam failure city of oxnard 2016 bouquet canyon reservoir bouquet canyon reservoir is located east of interstate 5 and north of castaic junction, highway 126. Failure of gravity dam occurs due to overturning, sliding, tension and compression. Water pressure is the most major external force acting on a gravity dam. Fontenelle dam was constructed by the us bureau of reclamation on the green river in wyoming in 196063, with a single line grout curtain. What is difference between gravity dam,earth dam,arch dam,buttress dam,barrage hindi quikr exam gravity dam. Earthfill dams are less rigid and more susceptible to failure. Evaluation of failure modes for concrete dams diva. An earth fill dam, like other types of dams, benefits. A concrete gravity dam is facing with a variety of failure mechanisms include dam sliding on the structure and foundation interaction surface.
119 1608 749 328 443 624 1281 116 900 309 1332 1654 426 261 1124 455 1600 1300 229 1384 81 422 969 1611 180 1310 279 1037 330 158 1331 954 1144 867 1566 490 995 407 1156 102 1265 431 1211