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In highway engineering
Highway engineering

Highway engineering is the process of design and construction of efficient and road safety highways and roads. It became prominent in the 20th century and has its roots in the discipline of civil engineering....
, subgrade is the native material underneath a constructed pavement. It is also called formation level.

Explanation
Subgrades are commonly compacted before the construction of a pavement, and are sometimes stabilized by the addition of asphalt
Asphalt

Asphalt is a sticky, black and highly viscosity liquid or semi-solid that is present in most crude petroleums and in some natural deposits sometimes termed asphaltum....
, soil cement
Soil cement

Soil cement is a construction material , a mix of pulverized natural soil with small amount of portland cement and water, usually processed in a tumble, compacted to high density....
, portland cement
Portland cement

Portland cement is the most common type of cement in general use around the world, because it is a basic ingredient of concrete, mortar , stucco and most non-specialty grout....
 or lime
Lime (mineral)

Lime is a general term for calcium-containing inorganic materials, in which carbonates, oxides and hydroxides predominate. Strictly speaking, lime is calcium oxide or calcium hydroxide....
. It is the foundation of the pavement structure, on which the subbase
Subbase (pavement)

In highway engineering, subbase is the layer of aggregate material laid on the subgrade, on which the base course layer is located. It may be omitted when there will be only foot traffic on the pavement, but it is necessary for surfaces used by vehicles....
 is laid.

Preparation of the subgrade for construction usually involves digging, in order to remove surface vegetation, topsoil
Topsoil

Topsoil is the upper, outermost layer of soil, usually the top 2 to 8 inches. It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biology soil activity occurs....
 and other unwanted material, and to create space for the upper layer of the pavement.






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Encyclopedia


In highway engineering
Highway engineering

Highway engineering is the process of design and construction of efficient and road safety highways and roads. It became prominent in the 20th century and has its roots in the discipline of civil engineering....
, subgrade is the native material underneath a constructed pavement. It is also called formation level.

Explanation


Subgrades are commonly compacted before the construction of a pavement, and are sometimes stabilized by the addition of asphalt
Asphalt

Asphalt is a sticky, black and highly viscosity liquid or semi-solid that is present in most crude petroleums and in some natural deposits sometimes termed asphaltum....
, soil cement
Soil cement

Soil cement is a construction material , a mix of pulverized natural soil with small amount of portland cement and water, usually processed in a tumble, compacted to high density....
, portland cement
Portland cement

Portland cement is the most common type of cement in general use around the world, because it is a basic ingredient of concrete, mortar , stucco and most non-specialty grout....
 or lime
Lime (mineral)

Lime is a general term for calcium-containing inorganic materials, in which carbonates, oxides and hydroxides predominate. Strictly speaking, lime is calcium oxide or calcium hydroxide....
. It is the foundation of the pavement structure, on which the subbase
Subbase (pavement)

In highway engineering, subbase is the layer of aggregate material laid on the subgrade, on which the base course layer is located. It may be omitted when there will be only foot traffic on the pavement, but it is necessary for surfaces used by vehicles....
 is laid.

Preparation of the subgrade for construction usually involves digging, in order to remove surface vegetation, topsoil
Topsoil

Topsoil is the upper, outermost layer of soil, usually the top 2 to 8 inches. It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biology soil activity occurs....
 and other unwanted material, and to create space for the upper layer of the pavement. This process is known as subgrade formation or reduction to level.

The load-bearing strength of subgrade is measured by California Bearing Ratio
California Bearing Ratio

The California bearing ratio is a penetration test for evaluation of the mechanical strength of road subgrades and basecourses. It was developed by the California Department of Transportation....
 (CBR) test, falling weight deflectometer
Falling weight deflectometer

File:FallingWeightDeflectometer.jpgA falling weight deflectometer, FWD, is a testing device used by civil engineers to evaluate the physical properties of a pavement ....
 backcalculations and other methods.

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