This is one in a series of Traffic Advisory Leaflets providing guidance on methods of working and innovative techniques aimed at reducing traffic congestion due to road works. The series is aimed at utility companies, highway authorities, contractors, equipment suppliers and others involved in road (or street) works. Each leaflet in this series is based on research carried out by TRL Limited on behalf of the Department for Transport and Transport for London. This leaflet gives guidance on the use of Core and Vac (coring and vacuum extraction) for repairing buried apparatus. The technique allows utility companies to open the road, gain access to their apparatus and reinstate the site considerably faster than is normally the case with conventional excavation methods. It can be very cost effective and it minimises damage to the structural integrity of the road. Core and Vac is not covered by the Specification for the Reinstatement of Openings in Highways. The use of technique will therefore require the agreement of the highway authority. Core and Vac was originally developed for the gas industry in the USA and is becoming increasingly used by gas and water industries in the UK. It is particularly suited to maintenance and repair of buried valves. Core and Vac is used on flexible and rigid construction pavements. Using specialist equipment (see Figure 1), it involves drilling a hole up to 600mm diameter through bound or concrete surface layers, removing the resulting core, then removing any unbound material through vacuum extraction to gain access to the apparatus. Following repairs to the apparatus, the unbound material is returned to the excavation and compacted in layers, although it is sometimes necessary to replace excavated fill unsuitable for re-use. Figure 2 shows previously extracted unbound material ready for reinstatement. The core is then grouted back into place to match the original surface level. (Author/publisher)
Samenvatting