Constructed naturally or artificially over streams, rivers or canals, dams serve to retain and control the flow of water. Regardless of their purpose and the type of operation, which varies widely, they have a common element: at some point in the course, the water is retained in the reservoir formed by the erected supports.
The specialist Fernanda Gouveia, coordinator of the Civil Engineering Laboratory (LEC) and professor of the Master in Engineering of Dams of the Federal University of Pará (UFPA), explains the functions of these structures: “The dams are used to supply water for human consumption and animals; for irrigation, recreation and landscaping; for the control of water quality and floods; for the minimum guarantee of downstream flow; navigation; aquaculture; electric power generation; and tailings containment “.
TYPES OF DAMS
According to Fernanda Gouveia, the typology of the dam is defined in function of its constructive form and the material used in its main body. Know each one:
• Earth dam: it is the most common in Brazil, characterized by very wide valleys and soft shoulders. It can be of homogeneous earth, constructed with only one type of material; or zoned land, which, due to lack of a lending area with clayey material sufficient to build the entire landfill, prioritizes the clayey core in the center. Because it is a less rigid structure, it allows more deformable foundations, transmitting low efforts to the foundations of any type of soil or rock.
• Concrete facing rockfall dam: consists of rockfills and concrete slabs on the upstream slope. Particular attention should be paid to the connection between the concrete slabs, since they rest on deformable means, constituted by the rock layer which may undergo significant settlements in the first filling.
It also requires attention to the connection between the concrete face and the foundation to ensure the tightness of this region. Advantages: faster construction, because it is independent of the climate; slopes more steep, providing smaller volumes of material and greater height of the structure. Disadvantage: the foundation must be in sound rock, as the structure can not undergo excessive setbacks.
• Buttress Dam: it is a type rarely used in Brazil and falling abroad, in favor of the types of gravity relieved. It is a hollow dam with a solid, upstream side, watertight, which is supported at intervals on the downstream side of a series of buttresses or support. It is a good choice in wide valleys where solid rock is rare.
• Relieved gravity dam: it is an alternative to the massive gravity dam. In this last one, the concrete is badly used because the requests are much smaller than the resistance of the concrete. In the comparison, it is observed that the relief of gravity relieved brings savings in the volume and decrease of the areas on which the subpressure and the interstitial pressure can act.
• Structural concrete dam with buttresses: it is formed by an upstream impermeable slab, supported by vertical buttresses, exerting compression in the foundation, greater than in the gravity dam. The foundation, in this case, must be rock with high stiffness.
If compared to gravity dams, the main advantages are lower volume and lower underpressure at the base. However, buttress dams require a more complex structural design and the use of a greater number of forms in the execution of the buttresses.
• Arc dams: are particularly suitable for narrow valleys and with good conditions of shoulders. These structures take advantage of the compressive properties of the concrete, transmitting the hydraulic thrust to the shoulders.
Advantages: use of less concrete in comparison with others; admit lower-quality foundations for dams on buttresses because a smaller part of the load is effectively transferred to the foundation. Disadvantages: They require good conditions and shoulders (usually in rock), and the concreting of the bow requires more sophisticated technology of rental, formwork, framing and application.
Dams can be made up of various functional structures necessary for their stability, operation and maintenance. Fernanda details:
To design and build dams, qualified professionals with experience and maturity are required. “This is the first great challenge of the enterprise”, emphasizes the teacher. The ideal is training at the postgraduate level, courses still rare in the country in the face of the volume of works. The UFPA campus of Tucuruí, through the Nucleus of Amazonian Engineering Development (NDAE), opened, at the beginning of 2016, the professional master’s degree course in Engineering of Dams and Environmental Management.