Development of the Modern Dams

Unlike past periods in history, the modern dam is designed using specific principles. The largest change in the design of a modern dam compared to the earlier dams, has been the formation of engineering schools. This changed the individualistic craftsmanship of engineering into a profession based on scientific principles. Engineers were subdivided into specific disciplines, increasing the advancements of both dam principles and construction methods.

The modern embankment dam has improved greatly with the increase in research on hydrology and soil mechanics. Henri Gautier was one of the first to study slope stability of different soils. His experiments determined the natural slope response of soils. As time went on, engineers were then able to choose different soils based on their internal angle of friction, to increase the height of embankment dam designs. Studies were conducted on how soil permeability changed for different soils. In 1186 Philipp Forchheimer, professor of hydraulics in Austria, developed a graphical method of Pierre S. deLaplace's formula of how water flows in a soil. This graphical method is commonly known as a flownet. The single most important theoretical development of soil mechanics was published in 1925 by Karl von Terzaghi. He found the explanation for why clays consolidate, by determining that the consolidation was caused by the dissipation of the water pressure in the soil pores. This finding led Terzaghi to the concept of effective stress, that is equal to the total stress minus the pore water pressure. This concept is still considered the single most important concept of modern soil mechanics. In 1980, the Nurek earth filled embankment dam in Tajikistan was completed. It stretched to a record height of 300m and had an embankment volume of 59 million m3.

The analysis of stress in structures in their elastic condition, the concepts of the modulus of elasticity, and safety stresses was introduced in 1819 by Louis M. H. Navier. These concepts were the beginning of understanding how the force in gravity dam designs acted and helped to increase the height, without increasing the amount of materials used.

Breakthrough advancements in arch dam design came in 1880's when Hubert Visher and Luther Wagnore developed a new method of arch dam design. This new method did not merely design the arch dams as astach of individual arches but as an interdependent system of arches. It also considered the median vertical section of the dam to be a cantilever fixed at the base. The distribution of the loads resulted in a considerable relief for the lower arches, and the upper ones had to partially support the cantilever. Throughout this period, the arch dam took on many new shapes.

With the modern ear, improved mechanical construction method have caused the greatest impact on all types of modern dam designs. Scraper, bulldozers and vibrators all grew in size, resulting in the modern dams being completed in record time. New techniques for placing concrete, have played a roll in the construction and design methods for gravity dams. Roller compacted concrete is among the newest techniques implements in gravity dam construction. In the early 1950's Switzerland introduced bulldozers to spread concrete, and vibrators were attached to caterpillar tractors. In the late 1970's early 1980's vibrations rollers replaced the tractor mounted immersed vibrating system. These new construction techniques have spread throughout the world at a rapid pace, increasing both the dimensions of dams and the speed of completion.

The number of new dams being built has decreased considerably. This trend will not be able to continue as the world population continues to increase and fresh water, irrigation and flood control needs increase as well. Engineers need to constantly search for a better solution, taking all aspects of design and the repercussions of that design into account. The past is a collection of design ideas, both good and bad, that should never be overlooked when faced with a new design challenge.

As time progress onwards, dams continue to grow in height and capacity. As they become larger, their impacts on society and the environments also increases. It is important that proper monitoring programs are setup to ensure that failure do not occur, because their effects will be devastating, One method of monitoring is a system of alarms downstream of the dam to warn of potential failures. the environment is an aspect that needs to be carefully controlled. With the growing size and capacity of modern dams, the environmental impact and awareness therefore increases as well.

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