Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 242 Applications and benefits Technical benefits associated with pipe jacking are: • Inherent strength of lining • Smooth internal finish giving good flow characteristics • No requirement for secondary lining • Speed of installation • Considerably less joints than a segmental tunnel • Prevention of ground water ingress by use of pipes with sealed flexible joints • Provision of invert channels in larger pipes to contain the dry weather flow of a sewer in a combined system • Less risk of settlement • Minimal surface disruption • Minimal reinstatement • Reduced requirement for utilities diversions in urban areas 8 An introduction to pipe jacking and microtunnelling 2 APPLICATIONS AND BENEFITS TECHNICAL BENEFITS The major applications for pipe jacking and microtunnelling include new sewerage and drainage construction, sewer replacement and lining, gas and water mains, oil pipelines, electricity and telecommunications’ cable installation, and culverts. Special applications include the installation of rectangular or circular sections for pedestrian subways, road underpasses and bridge abutments. The technique can be used to negotiate obstacles such as motorways, railways, rivers, canals, buildings and airfields in the path of pipe laying projects; to minimise the surface disruption frequently associated with open cut pipe laying methods in urban areas; or simply to provide a permanent underground tunnel construction. Pipe jacking is primarily used as an alternative to open cut excavations or other tunnelling methods. Significant lengths are attainable at larger diameters using mechanised techniques. Reference should be made to Tables 4c and 4d for specific recommendations. Construction methods are available to cope with both cohesive and non- cohesive soils in dry or water bearing conditions. Excavation techniques are also available for jacking through rock or mixed ground conditions, including cobbles and boulders.