22-04-2014, 01:02 PM
PROJECT ON EARTH DAM
EARTH DAM.docx (Size: 737.7 KB / Downloads: 22)
ABSTRACT
A dam is an obstruction on a river or stream to collect the water behind it, for multipurpose use, like irrigation canal, hydro power generation, flood control etc. The construction of earth dam which is Connecticut began with the arrival of the first colonial settlers in the 1630s. As the state’s economy evolved, dams are used for generate electricity, water supply for irrigation, flood control etc.
Earth dams are usually adopted where the materials for construction of gravitational dam is very high due to the poor transportation. And, also adopted were the structure should stand temporarily. This dam is also called as non rigid type of dam, because the whole structure of the dam is made of earth.
INTRODUCTION
Earth fill dams are non rigid type of dam and which counteract the thrust mainly by development of shear and cohesion. Earth dams are constructed of locally available soil and the discrete particles move along each other to resist the applied load. These dams appearing like a hills, fit into the landscape very well. The cross-section of the earth dam is usually trapezoidal, with horizontal top having 3-10m width. As at present, the maximum height of such dams achieved in our country is 125m. The earth dam can withstand seismic effects better than concrete dam. The construction cost of earth dams are much less than the concrete dam.
These dams are also called as temporary structure, due to its unpredictable life.
EARTH DAM
An earth dam is a structure made with highly compacted dirt used to slow or block water.
An earth dam is a dam built with highly compacted earth to retain the water bodies behind it, in the form of potential energy. This dam is classified as a type of embankment dam, being built in shape of an embankment which blocks the water way.
SITE SELECTION
For construction of earth dam U shaped flat valley or foothill plains are the best space to construct an earth dam.
Having made the choice of earth dam, next step is to investigate the quantity, quality ( by laboratory tests) and distance of different soils within the vicinity (nearby 10km range) of the site selected for the construction. The construction requires large quantity of water. Hence storage arrangements for use during summer and diversion during the last phase of construction are planned. The construction period is practically stopped during rainy season. Thus 2-8years period is required to complete the dam.
SITE REQUIREMENTS
i. VALLEY SHAPE: Steep V shaped valley is not suitable for earth dam since space for construction may not be available and proper bond with abutments may not be possible. Thus a U-V shaped flat valley is best suited.
ii. LOCATION: The foothill or sub foot hill plains are better suited since depth of soil layer will be greater (than a hilly stage) making the construction materials available, reducing seepage through foundation and proximity to the already cultured command.
iii. SITE FOR SPILLWAY AND OUTLET: The proper site for spillway, with good rock foundation at reasonable depth, necessary length of the spillway, site for tail channel should be available at one of the flanks or at a saddle along the rim of the reservoir.
iv. SOILS: Soils of sandy type for casing and clay type for hearting are required in very large quantity.
v. WATER STORAGE AND DIVERSION: Adequate volume of water, needed for construction and site for diversion of water should be available.
vi. LABOUR: Construction of earth dam requires large number of unskilled labours which should be locally available.