Pipe Jacking, Caissons, and Structure Jacking Note: This page deals with annulus lubrication. Regarding tunnelling methods which use additives, please click on slurry or epb/pumped muck. What causes high jacking load? When setting up for success on a difficult pipe jack it's worth considering how the ground conditions can affect overall friction. Sand and fines can migrate into the space between the pipe and the ground, limiting lubrication. Bentonite as a lubricant Standard grade bentonite is adequate for use in stable, clay-free ground. Its performance is dramatically improved by: * Using a programmable bentonite injection system * Adding supplementary lubricants such as TK60 or ClayCap - or moving to a fully synthetic polymer system Clay stickiness and swelling Clay (bentonite) based lubricants can be of limited use in swelling clay. Consider a specialist additive such as TK60 Jacking Lubricant or Glissaide which actively prevent clay from swelling and contain powerful polymeric lubricants. The Bank Holiday Test Pipe lubricated under bentonite, especially in clay, will inevitably gain load if not kept moving. Displave the entire annulus to Glissaide or TK60/Sloop to give maximum confidence about an easy start when you come back. Loss of Lubricant to the Ground Preventing lubricant loss to the ground can make all the difference. Choose Sloop or FibrouSeal to help maintain the annulus. These products can be added to your existing bentonite lubricant or used in a pure polymer mix. Gravels, Sands and Silts Falling into Annulus Counteract this by adding MX Polymer to the mix. MX has a powerful sand and gravel stabilizing effect. Annulus Maintaining lubrication for Caissons Similar problems can affect caisson lubrication, with the additional risk of losing lubricant if you have to underpin. Morrison Mud's Annulus Maintaining concept provides lubricants which hang and do not flow out catastrophically in the event of a leak. The Sloop system is the most often used - and we can provide special formulations on request. Salt water lubricants Most standard annular lubricants are ineffective in salt water. For best performance we recommend MX Polymer. This material is particularly effective in holding back slump loading of gravels and sands on to the pipe.
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