Soil mechanics, by examination of the subgrade of roads and highways, helps to determine which type of pavement (rigid or flexible) will last longer.
Load is transmitted through the slabs to the underlying subgrade by flexure of the slabs.
Flexible pavements are constructed of several thicknesses of asphalt or bituminous concrete layers overlying a base of granular material on a prepared subgrade.
It should be free from dust and other particles that could be blown up and ingested into engines, and it must be capable of spreading and transmitting an aircraft's weight to the existing subsoil (or subgrade) in a manner that precludes subsoil failure.
Rigid pavements are constructed of portland cement concrete slabs resting on a prepared subbase of granular material or directly on a granular subgrade.
In winter, a subgrade furnace blew hot air through a single giant duct.
The city needs to radically rethink its subgrade infrastructure with waterproof vaults for electrical, gas, fiber optic and cable lines.
Frank De Martini, the head of construction, also started out in the subgrade, crawling around in piles of rubble as a bomb-damage assessor.
He runs the council's studio program, which gives artists free space on the 91st floor, and he takes liberal advantage of the access that affords him, wandering around the subgrade, lamenting the whitewashing of his favorite graffiti, and scavenging the waste bins.
The subgrade, the six-level basement, contains galleries of enormous pipes; specially built motors that power the oversized air compressors; abandoned subway tracks that tunnel from nowhere to nowhere; and four blocks of debris-strewn loading docks visited steadily, like temple altars, by trucks leaving pallet after pallet of offerings.
