subgrade

American  

[suhb-greyd] / ˈsʌbˌgreɪd /

noun

1. the prepared earth surface on which a pavement or the ballast of a railroad track is placed or upon which the foundation of a structure is built.

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adjective

1. beneath the finished ground level of a project.

subgrade British  

/ ˈsʌbˌɡreɪd /

noun

1. the ground beneath a roadway or pavement

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Etymology

Origin of subgrade

First recorded in 1895–1900; sub- + grade

Example Sentences

“Reinforcing the ground below the tracks required removing any work already completed, excavating additional soil beneath 1400 feet of track, and installing new subgrade materials to provide the required stability,” according to WMATA.

From Washington Times • Oct. 1, 2022

The aggregates for the concrete may be distributed along on the prepared subgrade or may be stored in stock piles or bins at convenient points.

From American Rural Highways by Agg, T. R. (Thomas Radford)

Foundation.—The foundation or lower course consists of a layer of broken stone six inches thick placed on a well drained and thoroughly rolled earth subgrade.

From American Rural Highways by Agg, T. R. (Thomas Radford)

If stored on the subgrade, a traction mixer is employed which is drawn along the road as the work progresses, the materials being placed directly in the mixer.

From American Rural Highways by Agg, T. R. (Thomas Radford)

In level countries and with narrow roads, enough material may be excavated to raise the roadway above the subgrade in forming the side ditches by means of road machines.

From The Future of Road-making in America by Hulbert, Archer Bulter