Safety considerations, failure scenarios and various factors affecting the behaviour and performance of concrete arch dams

Abstract

Dams which were primarily used for irrigation and water supply in ancient days makes their presence inevitable through their important roles in other arenas such as flood control, hydropower development, navigation, sediment control and water quality etc., as well. The overall basin development depends largely on various dams constructed at various salient location. To the world population –presently at 8 billion- the demand for water which is growing at 2 to 3% annually will be a concern and dams render a helping hand in that perspective. Concrete dams plays a prominent role. The failures of concrete gravity and arch dams are rare compared to other types. Comprehensive studies on dams attributed the failure modes to overtopping, foundation problems, piping, sliding, structural failure, inadequate spillways, earthquake motions and faults in operations etc. Thermal loading is a concern when there are large variations in temperature. Earthquakes can become a cause of failure of dams depending upon salient characteristics of the event, quality of the rock constituting the foundation strata, material of the dam and the design criteria adopted. The design methodologies have undergone commendable changes from the linear-elastic static analyses to dynamic analyses and the design techniques are capable of incorporating non-linearity and also for simulating the near real scenario. The pseudo-static seismic methods gave way to dynamic seismic simulations using the time histories of the seismic activities already occurred with the help of various mathematical models and refined software. Concrete dams are no exception in failures, if they are not implemented and monitored as per the latest guidelines of national and international standards. Apart from seismicity, there are various factors influencing the behaviour and safety of dams. Concrete arch dams are often constructed to impound very large volume. Adoption of state of the art analyses techniques, design as per latest guidelines, studying the performance and behaviour, safety evaluation and continuous dam health monitoring are essential to avert any potential hazard to these invaluable resources. This paper reviews extensively, the various considerations towards the design, behaviour, performance and the failure scenarios of concrete arch dams.