What Is An Embankment & Why Is It Important In Road Projects?
Strong structures called embankments are utilised in building projects to withstand flooding and erosion. They offer access over sloping terrain and guard against flooding-related catastrophes. Notably, much thought should be given to design and material choice to ensure its efficacy and longevity. The functions of embankments and the procedures involved in building them are covered in this article.
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Embankments have a significant role in influencing our environment, from easing transit routes to assuring irrigation efficiency. Embankments serve two crucial purposes: they ensure efficient drainage and a strong base. This article will examine embankments in depth, looking at their varieties, advantages, and methods of construction.
What is an embankment?
A strong earthen structure known as an embankment is built to sustain a road or railway across low-lying terrain. Additionally, it was constructed to protect against flooding brought on by rivers or the sea. Embankments are essential for many earthwork tasks, such as building reservoir dams and runway foundations.
The design of embankments must take into account a number of elements. These consist of figuring out the ideal height, picking acceptable materials, and running stability assessments. Ground improvement measures are required to control the settling of the foundation soil when the embankment demands a high fill height or is built on unstable foundation soil.
India’s several types of embankments
Road embankments
These embankments are built to elevate the road level over the terrain or water below, creating a solid platform for moving vehicles.
Railway embankments
Like road embankments, railway embankments are constructed to raise the tracks above the level of the surrounding terrain, guaranteeing a straight and level track alignment.
River embankments
In order to stop floods and erosion, they are built along riverbanks. In times of strong water flow, these aid in keeping the river inside its allotted course.
Coastal embankments
To safeguard against the erosive effects of waves, tides, and storms, coastal embankments are built along coasts. These act as a barrier, stopping the infiltration of seawater and lowering the possibility of floods and coastal erosion.
Reservoir embankments
These are constructed to impound water and produce sizable bodies of water, such reservoirs or lakes. For the storage and control of water, the embankments are essential.
Airport runway embankments
In order to provide adequate drainage and stability for aircraft operations, embankments are frequently erected during airport construction to create a level platform for runways and taxiways.
Advantages of embankments
Flood prevention
As barriers for holding and rerouting water during times of severe rainfall or high river levels, embankments serve a critical role in flood management. They protect people and infrastructure by assisting in preventing flooding in nearby regions. Embankments reduce the likelihood of widespread flooding by directing water down defined paths, decreasing the damaging effects of floods on populations.
Irrigation
By building canals or water storage reservoirs, irrigation embankments make irrigation systems more effective. They make it possible for water to flow in a regulated manner, directing it towards agricultural areas, maintaining a steady supply for crop development, and raising agricultural production.
Protection from coastal erosion
The erosive powers of waves, tides, and storms are deterred by coastal embankments. They protect the shoreline and stop land loss in coastal regions by reducing erosion.
Embankment: The building procedure
An embankment forms the base for the various parts of the road surface in the case of transportation corridors. The height of the embankment varies depending on the needs of the project. According to the detailed design report (DPR) for road projects, it is constructed at the appropriate completed road level (FRL). The main steps in building a road embankment are as follows:
· Public utilities like electricity poles are moved after the area has been cleaned.
· The construction crew defines the embankment’s boundaries before beginning the earthwork by driving pegs into the ground at regular intervals.
· The group levels the initial ground and installs the first layer of the embankment.
· The materials are combined with water to start the compaction process, which is then rolled to achieve the minimum dry density stipulated in the DPR.
· The original ground is combined with the necessary quantity of water and compacted by a vibratory roller to get the requisite dry density if the dry density is less than 95% of the maximum dry density (MDD).
· The crew substitutes acceptable materials in the embankment foundation if inappropriate materials are discovered.
· The embankment material is applied in stages, each layer having a maximum compacted thickness of 250 mm.
· When water is needed, it will be evenly sprayed from a water tanker equipped with a sprayer without flooding the surface, and then completely mixed with soil by harrowing until the consistent moisture content is attained throughout the layer’s depth.
· In the event that the provided material is too wet, it is air dried and solar-assisted until the moisture level is acceptable for compaction. The optimal moisture content (OMC) range is the moisture content that should be present during compaction.
· In this compaction technique, a vibratory roller with a static weight of 8–10 tonnes is used.
· To establish the number of passes necessary for a certain kind of soil used in the embankment to meet the densities outlined in the Ministry of Road Transport & Highways (MoRTH) Section 300, the team performs compaction testing on a suitable length.
· The soil compactor is operated until the desired density is attained based on the trial results.
· According to MoRTH Section 300, the rolling operation continues until the desired density is obtained.
· According to the DPR, further layers are only applied when the last layer has been evaluated and approved.
Embankment: Components and their properties
Soil, gravel, fly ash, or a mix of these elements may be used as the embankment construction material. The selected material must adhere to the strict specifications listed in the DPR. According to the standards given by the engineer and the Ministry of Road Transport and Highways (MORTH), the materials used should be appropriate, whether they were dug out from the site or bought from authorised sources. The following are materials that are frequently used to build embankments:
Fine-grained soil
Low permeability, low shear strength, and high compressibility are characteristics of fine-grained soil utilised in embankments. Rapid work might weaken it and lead to unstable situations during construction. However, embankments constructed with fine-grained soil have demonstrated excellent earthquake resistance.
Coarse-grained soil
In the structural fill, filter, drain, and core zones, coarse-grained soils like sand and gravel are employed. These soils are less sensitive to variations in moisture, easily compactible, and permeable. They are, nevertheless, prone to runoff and wave-induced erosion.
Broad gradations of soil
Broadly graded soils exhibit characteristics of both fine- and coarse-grained soils due to their mixture of particle sizes. In comparison to fine-grained soils, they have lower hydraulic conductivity (the capacity of a fluid to move through pores and broken rocks), higher shear strength, and lower compressibility. Broadly graded soils are often quite resistant to earthquake damage when used to build embankments.
Embankment material properties
Maximum dry density (MDD)
1.52 T/cum for embankments upto 3 m height
1.60 T/cum for embankments greater than 3 m in height
Coarse material size
Less than 75mm
Liquid limit
Below 70
Plasticity index
Below 45
Embankment: Construction equipment required
· Hydraulic excavator
· Motor graders
· Dozer
· Dumper trucks
· Vibratory compactor
· Soil compactor
· Water tanker
· Tractor trolleys
· Survey kit
Embankment: Quality assurance techniques
· According to MoRTH requirements, measurements of random densities are made.
· With the use of techniques like sand replenishment and non-destructive testing, field density tests are carried out.
· During density measurements, soft spots are discovered, and further compaction is applied.
· The soft material is replaced with acceptable material and compacted in accordance with the prescribed compaction criteria if they are not satisfied.
· Test findings are documented according to authorised inspection and test plans in the relevant formats.
· The compacted embankment’s top layer’s alignment and levels are examined to make sure they adhere to predetermined standards.
· Testing operations are meticulously documented, including dates, places, and permission information.
In conclusion : embankments are essential for many building projects because they help with flood control, irrigation, and transportation. Filling height, material choice, concerns for settlement, and stability analysis are among the design factors for embankments. In order to guarantee the stability and quality of embankments, proper compaction management and testing are required. Construction of robust embankments is possible if the pertinent requirements are followed.
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