Highway drainage systems are installed to capture surface water run-off, to alleviate flooding and protect the fabric of the road.
Horizontal slip-forming is a method of constructing continuous concrete elements such as drainage channels. Construction is by means of a specially-designed machine consisting of a mould of the required dimensions and vibrators to compact the concrete. The machine is self-powered and is mounted on wheels or tracks. A stiff concrete mix is used and the machine moves forward at such a rate that the concrete emerging from the rear is self-supporting. Slip-forming offers the advantages of speed, the ability to produce a monolithic structure, economy of operation and the elimination of heavy lifting.
Flexibly-jointed concrete pipes (to BS 5911: Part 100) are manufactured with internal diameters ranging from 225mm to 2.4m. The length is generally 2.5m though shorter lengths are available. Bends and junctions are also available. The joints incorporate fixed or loose seals. For trenchless construction, jacking pipes (to BS 5911: Part 120) are manufactured in diameters from 900mm to 3m, in lengths up to 2.5m. Joints may be set into the wall or by means of steel bands. Micro-tunnelling pipes are produced in diameters from 450mm to 900mm, with lengths up to 2.5m. Non-circular pipes (ovoid and elliptical) are available in a range of sizes with a standard length of about 2.5m.
For more information refer to the British Precast Drainage Association at www.precastdrainage.co.uk or Interpave at www.paving.org.uk.