Trenchless Technology

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Trench less technology is the science of installing, repairing and renewing underground Pipes, ducts and cables using techniques which minimize or eliminate the need for excavation. It can reduce environmental damage, Social costs and produce an alternative to open trench method of installation, renewal and repair .It includes in, development of all kinds of underground napping techniques, tunneling devices and specialist materials and equipment. Trench less technology is basically making a tunnel below the surface and staling service lines like water or gas pipes, electric or telecommunication cables etc. with out any disruption to the public. It also makes it possible to install the utilities under rivers canals and other obstacles with no disruption of flow and with minimum or no damage to the environment.

2. TRENCHLESS TECHNOLOGY METHODS

Trenchless technology methods system have been categorized in to two groups :

New installation

Rehabilitation and Renovation

 
NEW INSTALLATION

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Methods for installation of a new pipeline or duct, including dealing with service connection are:

  1. Microtunelling
  2. Horizontal directional drilling
  3. Short drive system
  4. Guided drilling
      1. MICRO TUNNELING

 

Controlled excavation ? steerable ?Less than 1000mm diameter ?Medium length

??????????? Micro tunneling is a term which is used to describe remotely controlled mechanical tunneling systems where the spoil is removed from the cutting head with in the new pipe line which is advanced by pipe jacking.

??????????? Micro tunneling machines have now been developed to work from drives hafts in almost all types of ground conditions. The cutting head has to be carefully selected to deal with the expected ground conditions, with the appropriate cutting tools and crushing devices for the range of gravels, sands, slits, and clays.

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??????????? The only excavating required from the service is for drive and receptions shafts. Spoil may be removed from the face by an auger running through the newly installed pipeline to a skip in the base of the drive shaft.

??????????? Alternatively, water or bentonite? may be used to convert the soil into slurry at the cutting face. The slurry is less then pumped to the surface where the solids are separated before disposal .

??????????? Microtunneling is used extensively for sewerage work where surface disruption has to be minimized. Machines are now available to drive 100mm or more in soft ground for sizes 100mm diameter upwards. from drive shafts of less than 3mm diameter.

??????????? Micro tunneling system has been developed in which temporary steel tubes are jacked in and removed at the next manhole position, the new pipeline following in the established bore. In microtunnelling, the only indication on the surface is the presence of a control container with a hoist for lowering pipes into the drive shafts. Noise levels and traffic disruption are minimised

2.1.2 HORIZONTAL DIRECTIONAL DRILLING

Steerable heavy, powerful rig-Large size range ?Long distances

??????????? Horizontal drilling systems are nowadays widely used for installing pressure pipes under major obstacles such a motor way intersections, large rivers and airports runways.

??????????? A small rotating and steerable drill bit is launched from the surface at an angle 10-15 and is used to drill 90mm mud filled diameter hole. During the drilling operation a 125mm diameter washover pipe is drilled over the pilot string and following? some 100mm behind the head. Alternate drilling then continues on the pilot string is removed and the bore is enlarged by a rotating barrel reamer attached to and pulled back by the wash over pipe, drilling mud being used to llushed away the cuttings and to support the reamed hole. Subsequent caming continues until required diameter is achieved. The product pipe is less than attached to the reaming head and pulled through the bore drives of more than 1.5km and of up to 1200mm diameter have been carried out.

      1. SHORT DRIVE SYSTEMS

Essentially unsteered ?Soil displacement

Auger Boring utilizes a rotating head to excavate the soil, which is transported by auger flights operating in a casing to the drive pit. The head is recovered at an exit pit or in the trench cut for the adjacent length of pipe line. Auger boring is used in the range of 100-1000mm diameter
 

 

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Augur Boring

Impact Moling in which a percussive mole is launched from a drive pit to displace the soil and from a bore is widely used. The new conduct is normally drawn in behind the mole. They are used to install services for all utilities.

Rod Pushing is a technique in which a bore of about 50mm diameter is formed by displacement. A rod is advanced by a straight hydraulic push and the pilot hole may be back reamed to the required size. The technique is used for the installation of pipes and conduits up to 15mm diameter over lengths of 30-40mm.

 

 

Pipe ramming and Thrust boring are similar processes where a casting, usually steel, is driven through the ground from the drive pit to the exit pit.? Accumulating spoil is removed by compressed air and water after completing the bore.? Pipe ramming is suitable for most types of soil but not suitable where there are solid rock formations.? It is said to be a cost saving alternative to open trenching, angering or pipe jacking methods.? Usually pipes up to 2000mm diameter can be laid using this technique depending upon the equipment uses.

2.1.4 GUIDED DRILLING
Steer able small rig-Sallow drilling-Medium length

??????????? Guide drilling employs an excavation or soil displacement with compact lightweight rig for rapid mobilization.? Small diameter jets mechanized cutting tools or displacement heads attached to a flexible drill string are positioned to form a bore as the head is thrust forward.? The drilling head is launched from the surface at an inclined angle. Controlling the orientation of a slant face at the head effects steering in both vertical and horizontal planes.? Monitoring of the alignment takes place using a transmitter in the head and a locating device at ground level.

 

 

Guided Drilling

 

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