Highway Embankment Construction Practice | Construction Practice for Highway Embankment

An embankment is an area of the volume of earth materials which use to raise the grade of a highway embankment above the level of the existing ground surface

A filling of the material refers to a volume of earthen material that is placed on the ground and compacted for the purpose of filling in a hole or depression

Top 10 Tips for Highway Embankment

Here The Civil Experiences can try to explain in 10 steps all about the Highway embankments I read and learn from reference books and give my conclusion

Clearing and grubbing

The First operation to be done in highway embankment earthwork is to Clearing and dig up the land area

Clearing and grubbing, Consist of removing obstacles like trees, stumps, roots, shrubs, undergrowth, rubbish and other objectionable material from the area to be occupied by the embankment of the highway

This step is useful for all kinds of civil engineering work like building construction, road construction, bridge construction etc

Stripping and Storing of Topsoil

In areas where the embankment soil is not useful for the growth of turf and vegetation then the topsoil should be stripped and stored so that we can use that soil later to laid as on the embankment slopes.

So that embankment is free for vegetation and other plats

Compaction of the original Ground

Embankments Slopes with a height of fewer than 0.6 m above the ground impose high-intensity stress on the root soil. Such low heights are generally avoided

In situations where it is unavoidable the density of the native soil should be satisfactory

If its compaction is less than 90 per cent of Proctor’s density then the original ground should be brought to compaction of at least 100 per cent of Proctor’s density by loosening, watering and rolling in layers of 25 cm.

This treatment should extend to a depth of 0.5 m. If the next 15 cm below this depth does not have compaction of at least 90 per cent, it should be made up to at least 95 per cent

Benching of Steep Slopes

When the embankment is constructed on high hillside slopes, it is necessary to settle the surface of the hill slope with benches having a height of 0.5 m and a width of 1.5 — 3.0 m, to add to the stability
These benches should have a uniform fall towards the hill-side

Borrow pit Practice

The practice has been recommended by the Indian Roads Congress for borrow-pits are listed below

• Borrow pit should be as rectangular in shape and near to the boundary road as possible
• For future widening there is No borrow pit should be located within 5 meters from the toe of the embankment
• The depth of borrow-pits should be so regulated that they do not cut an imaginary line having a slope of 1 in 4 projected from the edge of the bank. The maximum depth should be limited to 1.5 m
• Avoid continuously drugging of Borrow-pit. Ridges not less than 8-meter width should be left at intervals not exceeding 300 meters. Small drains should be cut along the banks to facilitate drainage
• The depth of borrowed pits in Land temporarily acquired should not exceed 45 cm
• Borrow pits should not be dug within 0.8 km of towns and villages, to ensure that water not collecting in them to breed mosquitoes

Deposition of Soils into layers

Generally, soils for embankments should be deposited in multiple layers, and each of the layers is compacted before the next layer is laid on an already laid layer

The depth of layers is generally restricted to 25 cm. Where sheep's foot rollers are used for compaction, the depth should not exceed the length of the tamping feet by more than 5 cm

The soil clods should be broken to have a maximum size of 15 cm. In the top 50 cm of the embankment, the maximum size should be still less, say 6 cm

Earthwork is done in India generally by manual labour, and in limited cases by the use of excavators, scrapers, dozers, graders and dumpers. Scrapers are able to dump and spread in layers in one Operation.

But if dumpers and trucks are used, the soil is first dumped and then spread by a grader or a dozer

Moisture Content

Soil tests would have indicated the OMC (optimum moisture content) at which the density would be maximum

• If the natural soil has less moisture than indicated by these tests, extra water is sprinkled on the layers
• If the natural moisture content is high than the desired moisture, the soil is allowed to void less before rolling is done

Highly expansive soils like black cotton soil If allowed, are normally compacted at a moisture content 3 to 4 per cent above the optimum to a density not exceeding 90 per cent of the standard Proctor dry density

Compaction Equipment

Needed Mechanical equipment to gain the desired compaction. In India, the standard equipment used is the three-wheel steel-tyred roller. Other equipment like Sheepsfoot roller, pneumatic tyred roller, vibratory roller and power rammers are also used

Density to be Achieved

Compaction of the lift of earthwork is carried out in order to gain satisfactory density

The density to be aimed at depends on the type of soil and the position of the layer. Higher densities are desired in the top 0.5 m of the embankment Immediate below the pavement than in the other portions

Compaction Procedure and Control

Compaction equipment is selected keeping in view the type of soil to be handled and availability of equipment

The exact number of passes to be made on the soil layer needs to be determined According to what achieve in the field the compaction standards selected

Preliminary investigations are made on a test area 20 m long and 5 m wide and the soil layer is prepared with due regard to lift thickness, clod size and moisture content

The increasing number of passes with the roller is made and the dry density determined after each number

An increasing number of passes are made with the roller and the dry density determines for each number later. Normally 4, 6 and 8 passes should be adequate for smooth wheel rollers and 4, 8 and 16 passes should be adequate for sheepsfoot rollers for trial purposes

The number of passes required to achieve the desired density can then be selected

Blasting Operations

Where hard rock strata are involved in cutting, as in mountain roads, blasting is resorted to. The charging hole should be drilled to the required depth and in the right places

Safety precautions in the storage Of explosives in magazines and in blasting operations are very essential. The material obtained from blasting lands a variety of uses, such as pavement construction, masonry work, retaining walls, lining of side drains, etc

Safety previews in storage are very much needed in explosives and blasting operations in magazines.

Explosion finishing material for various types of uses, such as pavement construction, masonry work, retaining walls, side drain lining, etc. The material should be recovered and stacked for reuse

Also Read:

Highway Engineering MCQs

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