Профессиональное развитие будущих инженеров-строителей средствами иностранного языка: Лексический практикум по английскому языку. Трубникова Н.В. - 79 стр.

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found, a simple rock-filled pit can be used. Slow absorption is overcome by

constructing a perforated precast concrete, dry stone or brick pit, which stores

the rainfall quantity. The stored volume is found from an assumed steady rain-

fall of 15 mm/h over a period of 2h. This is exceeded around once in 10 years,

so there may be occasional flooding for short periods. A soakaway pit is circu-

lar with its depth equal to its diameter.

Storage

An artificial pond or lake, or even an underground storage tank, will be

necessary if the expected run-off from a curtilage is at a greater rate than could

be accommodated by a sewer or watercourse.

Materials for drainage pipework

Traditionally, glazed vitrified clay (GVC) pipes have been used because

they represent an efficient use of UK national resources. The finished internal

surface of GVC pipes offers less frictional resistance to flow than that of con-

crete pipes and is resistant to chemical attack and abrasion. Rigid joints consist

of a socket and spigot cemented together. The brittle nature of such pipe runs

has led to the introduction of flexible joints, which can withstand ground

movement due to thermal and moisture variations and settlement of buildings.

Plastic and rubber sealing ring joints allow up to 5° of bending and longitudinal

expansion and contraction. Pipe sizes range from 75 to 750 mm in diameter.

Spun concrete drain pipes of diameter up to 1.83 m with oval cross-

sections, which maintain flow velocity at periods of low discharge, are used.

Plastic sleeves with rubber sealing rings give joints flexibility and a telescopic action.

Asbestos cement pressure pipes in lengths of up to 4 m have been used

because of their lower weight. Flexible sleeve joints with rubber ring seals are

used. Diameters from 100 to 600 mm are produced.

Pitch fibre pipes are formed by impregnating wood fibre with pitch. They

are lightweight and can be used for some drainage applications. Lengths of

2.5 m are easily handled and can be hand sawn. Push taper joints are made us-

ing a hand-operated chamfering tool. Pipelines have flexibility and require

well-selected backfill and careful protection during site work. Hot fluid or

chemical discharges may lead to the early collapse of the pipe from ground