Geological Investigation for Dam Siting in the Kurdistan Region

Abstract

Dams are complex structures constructed to prevent or restricting the flow of surface water or underground stream, for this reason, the design of dam is conceived as a whole, taking in to consideration the relationship between the individual parts. Every dam design start with the selection of the most suitable site, chosen so that the scope of special foundation work is minimized and the cost of construction are kept as low as possible, taking in to account the risk of failure of the structure during building, operation and commissioning, therefore, when conducting geological survey for selection of a dam site, the first objective method must be the identification of the different types of rocks that make up the area and determines their distribution in relation to the underlying structure because of the complexity of their structure, and the failure to understand the crucial nature of this relation will cause some of the most tragic civil disasters in the area, in addition the zone of weakness in the rock mass and the tectonic factors responsible for them must be delineated to have complete information about the site and then designing and constructing the dam based on the data that have been obtained by geological survey. Geological and tectonic conditions are fundamental factors in selection a dam site and the type of construction chosen for the dam. They largely determine the safety of the foundation and the costs of construction. All types of dams can be constructed providing the bedrock is strong and the attitude of bedding is favorable and there are no discontinuities that will allow the rocks to move under the stress and hydraulic pressure created by water and construction of the dam and its foundation. When structures for the retention of water are being designed, the proper selection of the dam site and the dam height are crucial but the choice of the most suitable type of dam construction is equally important. Basically, dams are classified according to the type of structure and the construction material used. Thus, there are dams constructed using non-cohesive material (earth-fill and rock fill embankment dams, combined types of earth /rock-fill dams, and hydraulic fill dams) and dams constructed of cohesive materials (masonry and concrete). The latter are divided in to three main groups (gravity dam, arch dam, and buttress dams. The main construction material used for these is concrete in addition to the basic types listed above, there are a number of transitional types, e.g., combined earth-fill and concrete gravity dams, in which the concrete structure functions as a channel to divert high water through the dam, and there are dams based on special construction techniques in which prefabricated elements are used, metal, and chamber dams. Nowadays, water reservoirs are mostly designed for multipurpose uses. This follows from the need to balance the demand for multiple uses against the limitation on available sites and the supplies of water available. This comprehensive concept of the dam is justified by the need to balance water-management against energy demands, domestic and industrial uses, ecological pressures and other factors in an economically efficient way.

Dams are complex structures constructed to prevent or restricting the flow of surface water or underground stream, for this reason, the design of dam is conceived as a whole, taking in to consideration the relationship between the individual parts. Every dam design start with the selection of the most suitable site, chosen so that the scope of special foundation work is minimized and the cost of construction are kept as low as possible, taking in to account the risk of failure of the structure during building, operation and commissioning, therefore, when conducting geological survey for selection of a dam site, the first objective method must be the identification of the different types of rocks that make up the area and determines their distribution in relation to the underlying structure because of the complexity of their structure, and the failure to understand the crucial nature of this relation will cause some of the most tragic civil disasters in the area, in addition the zone of weakness in the rock mass and the tectonic factors responsible for them must be delineated to have complete information about the site and then designing and constructing the dam based on the data that have been obtained by geological survey. Geological and tectonic conditions are fundamental factors in selection a dam site and the type of construction chosen for the dam. They largely determine the safety of the foundation and the costs of construction. All types of dams can be constructed providing the bedrock is strong and the attitude of bedding is favorable and there are no discontinuities that will allow the rocks to move under the stress and hydraulic pressure created by water and construction of the dam and its foundation. When structures for the retention of water are being designed, the proper selection of the dam site and the dam height are crucial but the choice of the most suitable type of dam construction is equally important. Basically, dams are classified according to the type of structure and the construction material used. Thus, there are dams constructed using non-cohesive material (earth-fill and rock fill embankment dams, combined types of earth /rock-fill dams, and hydraulic fill dams) and dams constructed of cohesive materials (masonry and concrete). The latter are divided in to three main groups (gravity dam, arch dam, and buttress dams. The main construction material used for these is concrete in addition to the basic types listed above, there are a number of transitional types, e.g., combined earth-fill and concrete gravity dams, in which the concrete structure functions as a channel to divert high water through the dam, and there are dams based on special construction techniques in which prefabricated elements are used, metal, and chamber dams. Nowadays, water reservoirs are mostly designed for multipurpose uses. This follows from the need to balance the demand for multiple uses against the limitation on available sites and the supplies of water available. This comprehensive concept of the dam is justified by the need to balance water-management against energy demands, domestic and industrial uses, ecological pressures and other factors in an economically efficient way.