Subgrade
In transport engineering, subgrade is the native material underneath a constructed road,[1] pavement or railway track (US: railroad track). It is also called formation level.
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Layers in the construction of a mortarless pavement: A.) Subgrade B.) Subbase C.) Base course D.) Paver base E.) Pavers F.) Fine-grained sand
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Section through railway track and foundation showing the sub-grade
The term can also refer to imported material that has been used to build an embankment.
Construction
Subgrades are commonly compacted before the construction of a road, pavement or railway track
gollark: In some of the sillier ones you effectively have some sort of secondary time axis (because if history "was" X but is "now" Y that implies some sort of metatime).
gollark: Depends on the model of time travel I guess.
gollark: https://m.imgur.com/a/wpZ4w
gollark: (You know what, I'll link the imgur page, downloading stuff from imgur is nightmarish)
gollark: (Yes this is for some reason a long thread on some other platform as an image on Reddit. I don't have a better format available and it's relevant-ish)
References
- http://www.highwaysmaintenance.com/drainage.htm The Idiots' Guide to Highways Maintenance highwaysmaintenence.com
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