On of the principle economic advantages of the earth dam is that nature has already fabricated the construction materials. So nature has placed them free of charge at this site.
In some cases only one type of soil is readily available. Therefore, the principle design problem is to determine the most economical dam that can be made from it.
- If it is an impervious soil. Firstly, the design consist of a homogeneous embankment with only a small amount of pervious material to control internal seepage.
- If it is a pervious sand and gravel. In other words is dam with a very thin core may be used where enough impervious is available to make a core.
- At the other extreme are sites with a great number of varied soils. For instance, these sites can be incorporated in different combinations into the embankment. In such case it in advisable to plan a zoned dam with the finer and more impervious materials placed in an internal core. The coarser materials utilized to provide strength and drainage in upstream and downstream zones.
- Where 2 (two) types of soil occur in horizontal layers in the same borrow pit. As a result, they can either excavated together and blended into single material with intermediate properties.