Module 4.docx

Module 4 EARTHWORK: Excavation is a process of cutting or loosening and removing earth including rock from its original position, transporting and dumping it as a fill.Earthwork primarily involved the following process. 1. Excavation of soil or shifting of the soil. 2. Loading, transportation and unloading of soil. 3. Placing and compacting of the soil. Depending upon the quantity of work, site conditions availability of recourses these works are carried out by various method and equipments. Excavation Soil is required to be excavated at site for various purposes. Some of the purposes of soil excavations are – 1. Removal of soil to level the ground. Example, cutting of hill. 2. For filling the ground at other places for creating vertical profiles of road. 3. Construction of side drains. 4. Super elevation purposes for raising outer edge of road Commonly used excavation are – 1. 2. 3. 4. 5. 6.

equipments

Bulldozers Power Shovels Scrapers Dragline Clam Shell Backhoe

for

the

Transportation The equipments used for excavation are also used for transporting for a distance, depending upon ground conditions. Many a time, the soil needs to be transported to other places which are not adjacent to the excavation site. The equipment used for transportation is also called haulers. a. b. c. d. e.

Belt conveyers Tippers Truck Dumpers Graders

Embankments When it is required to raise the grade line of highway above the existing ground level it becomes necessary to construct embankment. It depends on, Height, filler material, settlement, stability of foundation and stability of slopes. Construction of embankment  

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Rolling the soil in relatively thin layers or by hydraulic fills Each layer is compacted to a satisfactory degree of density before placing next layer. Compaction is carried out to optimum moisture content Thickness of layers is ranges 10 to 30cm. If the pavement is constructed before the settlement or the fill is complete it is likely to fail.

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Subgrade: The subgrade is the compacted soil layer that forms the foundation of the pavement system. Subgrade soils are subjected to lower stresses than the surface, base, and subbase courses. Preparation of subgrade: 

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The sites should be cleared off and top soil consisting of grass, roots rubbish and other organic matter are to be removed. The grading operation is started so as to bring the vertical profile of subgrade to designed grade and camber. It is most essential to compact the top of subgrade , upto a depth of about adequately before placing the pavement layer Bull dozers, scrapers and blade graders are useful equipment to speed up the work.

Soil compaction: Soil is compacted to obtain the desired density. The optimum density is obtained on a certain moisture content of the soil. Generally, the right amount of water is mixed before compaction the soil.

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Kneading Vibration Impact

Various compaction equipments are a. Smooth wheel roller b. Pneumatic tired roller c. Sheep foot roller d. Vibratory roller equipment – i.

Dropping weight type

ii.

Pulsating hydraulic type

Pneumatic tired roller

Factors influencing the compaction are,   

Moisture content Amount and type of compaction Soil type and stone content

For different types of soil, different compaction equipments are used. Single equipment is not effective for all types of soil. A roller compacts the – 

Sheep foot roller

Pressure 2