Chapter 10 

 EARTH DAMS 



Thomas A. Middlebrooks 



Chief, Soil Mechanics Branch 



Office of the Chief of Engineers 



Department of the Army 



Washington, D. C. 



The major civil works activity of the Corps of Engineers is the con- 

 struction and maintenance of dams and levees for flood control and 

 navigation purposes. More than one half of the dams and all the 

 levees are earth structures founded on a variety of geologic formations 

 varying from sound rock to overburden soils. An application of soil 

 mechanics principles to the design of these earth structures has re- 

 sulted in safe and economical construction. However, soil mechanics 

 is by no means an exact science and is dependent in a large measure 

 on a proper understanding of geologic formations to interpret the 

 results of foundation explorations. In the writer's opinion, close co- 

 operation between soils engineers and engineering geologists is essen- 

 tial in the design and construction of earth dams and levees. Investi- 

 gational, design, and construction features of earth dams are covered 

 in this chapter with specific reference to soil mechanics and geological 

 aspects of all phases of the work. Details of exploration and design 

 have been purposely omitted because they are adequately covered 

 in other publications. 



GENERAL FEATURES 



The selection of a dam site involves many factors, among which 

 the geologic and soil mechanics features are of prime importance. 

 Usually a site study must be confined to a limited reach of river 

 channel in order that the dam may perform its required function. 

 Unless conditions are obviously favorable at a particular location, 

 regional geology should be studied. During the preliminary studies 

 the site having the most favorable topographic features for the lo- 

 cation of the dam and the spillway is selected for more detailed 



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