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Types and Properties of Embankment Materials
Types and Properties of Embankment Materials: An embankment is a man-made mound made of earthen materials for example, stone or soil that is ideally compacted to accommodate the elevation of a highway or railway above the current ground floor.
In dam construction, the term “embankment” refers to successive layers of mud, such as dirt, sand, clay, or rock, with the most impervious materials forming the foundation and more permeable materials on the downstream and upstream sides.
We will address the qualities, properties, forms, and tests of embankment materials in this article.
Different Kinds of Embankment Materials
Soil with a Fine Grain
The embankment’s fine-grained soil does have a low permeability, a low shear resistance, and a high compressibility. Pore pressure is increased in this form of material mostly as a result of accelerated building operations, which results in decreased shear strength and inherently unstable situations during construction.
Compressibility of fine-grained soils used for embankments varies according to the soil’s properties and the conditions of placement. Dams and bunds built with fine-grained natural soil have shown a high level of resistance to earthquake damage.
Soil with a Coarse Grain
Coarse-grained soils have been used in fill zones, or shells, as well as in specialized filter and drainage areas within embankments. Coarse-grained soils composed primarily of sand and gravel are being applied in core zones, particularly when the amount of fines exceeds 20%.
Sands and gravels with less than around 5% fines by dry mass are pervious, simple to compress, and have a low susceptibility to moisture changes. Coarse-grained soils are particularly susceptible to surface erosion caused by wave action and runoff.
Soils of a Wide Range of Grades
Broadly graded soils contain a wide variety of particle sizes and exhibit engineering properties in between fine- and coarse-grained soils. In contrast to fine-grained soils, these types of soils usually have a lower hydraulic conductivity, a higher shear strength, and a lower compressibility.
Colluvial and boulder sedimentary beds also have large quantities of broadly graded soils suitable for embankment construction. In general, embankments built of widely graded soils are very resistant to earthquake impact.
Properties of Embankment Materials
Particle size gradation
A well-graded material is a combination of 2 or more soil types, typically granulated and fine-grained soils. There is no commonly recommended gradation scale for fill materials, but the overall particle size does not exceed 100 mm.
Low-density materials have the advantage of transferring less dead weight to the underlying soil which supports an embankment. In any case, there are no defined minimum or maximum unit weight specifications, either prior or after compaction.
This feature of embankment material indicates how well compacted fill material drains excess moisture.
While shear strength characteristics are not always defined for earthen fill materials, they are calculated by tri – axial compression or direct shear testing and used to calculate an embankment’s slope stability.
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