TRENCHLESS TECHNOLOGY (No-Dig Technique)

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TABLE OF CONTENTS• Introduction• Open Trench Method• Advantages of No-Dig Technology• Trenchless vs Open cut Method• Methods of Trenchless Technology• Pipe Bursting• Micro-Tunneling• Horizontal Directional Drilling• Trenchless Technology in INDIA• Conclusion

INTRODUCTION

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 is basically making a tunnel below the surface and installing service lines like water or gas pipes, electric or telecommunication cables etc. without any disruption to the public. It can reduce environmental damage, social costs and produce an alternative method to open trench method of installation, renewal and repair .

Trenchless technology is a type of subsurface construction work that requires few trenches or no continuous trenches.

Open Trench Method

 A trench is excavated running parallel to the old water main and the new pipe is laid in this trench. The technique is suitable for all pipe materials, however, disruption to road users is greatest and costs of reinstallment can be high.

In the picture, an open trench water mains renewal is in progress in a residential area . The trench has been excavated and the new pipe is in the process of being installed.

Vs

TRENCHLESS OPEN-CUT

DIFFICULTIES IN OPEN TRENCH METHOD

As the open trench is going to create obstruction on roads i.e. busy areas, diversions have to be provided before start of any digging work.

As the obstruction is created, the traffic has to be rerouted causing traffic jams.

Original users of the road have to undergo hardships in the form of additional travel as well as time.

Another difficulty, which is encountered very often is the damage caused to other service lines or cables present underground, providing temporary supports to these lines during the construction is cumbersome and costly affair.

While cutting open trenches, trees, shrubs, gardens etc. may have to be destroyed damaging the environment.

If any rehabilitation or renovation is required, the trenches once cut and refilled should again be cut through out and refilled causing difficulties to the public i.e cutting and refilling is required at frequent times.

Trenches left open overnight should be fenced and barricaded. Hand of mechanical signs should be used where necessary.

ADVANTAGES OF NO-DIG TECHNOLOGY•It reduces damages of valuable surface.•It reduces the danger of improperly compacted excavations.•It saves resources.•It is accident free.•It avoids traffic jam.•It saves underground space (pipe busting).•It reduces the impact on the environment.•It is possible to lay service lines across railway track, narrow lanes etc. When open trenching is impossible.•Presence of a canal, pond, river etc. across the root poses no problems to the trench less technology systems.•Without disturbing the traffic and life on the surface, the lines can be laid below ground in a much shorter time by using this technology.•For replacement, repair and rehabilitation of old water and sewer lines in cities, it is very helpful to use trench less technology without disturbing the normal life on the surface.

Trenchless v/s Open-CutOpen Cut Construction Trenchless Construction

Overcut for Trenchless Installations

Import Material for Open Cut Construction

Undisturbed Native MaterialRoadway Reconstruction

ADVANTAGES & DISADVANTAGES Disruption: Traffic delays are reduced or eliminated, as is heavy truck traffic

associated with culvert excavation deep below the roadway.

Speed of installation: Construction often takes less time, regardless of the road fill depth.

Less engineering: Less surveying, fewer design calculations, and fewer drawings and specifications may be required.

Safety: Many safety concerns associated with steep-excavation slopes, work inside trench boxes, and worker exposure to traffic may be eliminated or reduced.

Environmental effects: Less soil is disturbed so impacts on adjacent organisms and water bodies can be reduced significantly.

TRENCHLESS TECHNOLOGY METHODS

1. Rehabilitation & Renovation 1.1) Pipe bursting 1.2) Pipe eating 1.3) Retaining the existing pipes 1.4) Localized repair

2. New installation 2.1) Micro-tunneling 2.2) Horizontal directional drilling 2.3) Short drive system 2.4) Guided drilling

Pipe Bursting In this method an existing pipeline can be replaced with a pipeline of the

same or larger dimension without opening up the ground.

It is especially useful in areas where the load on the system is more than the existing pipe can handle and replacement is required.

The method uses a mole as a bursting head that is drawn through the existing pipe crushing it as it moves forward and replacing it with a new PE (polyethylene) pipe.

The main advantage of this system is that a small power source can be used to drive the mole with minimum time.

Upsizing from 100mm diameter to 225mm diameter is now well established, and pipes of up to 600mm diameter have been replaced.

Pipe bursting is of 2 types : Pneumatic Pipe Bursting Static/Hydraulic Pipe Bursting

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

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.

The only excavating required from the service is for drive and reception 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.

Water may be used to convert the soil into slurry at the cutting face. The slurry is then pumped to the surface where the solids are separated before disposal.

Micro tunneling is used extensively for sewerage work where surface disruption has to be minimized. It provides the necessary degree of accuracy in gravity lines.

Considerable advances have been made in recent years. Machines are now available to drive 100m or more in soft ground for sizes of 100mm diameter pipes from drive shafts with a high degree of accuracy.

Horizontal Directional Drilling

It involves steer able tunneling systems for both small and large diameter lines. It is two stage process.

First stage consists of drilling a small diameter pilot hole along the desired centerline of a proposed line.

In the second stage the pilot hole is enlarged to the desired diameter to accommodate the utility line and to pull the utility line through the enlarged hole.

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

Pilot hole is 3 inches in diameter and is drilled with an inclined carriage, typically between 5 to 30 degrees which pushes the drill rod into the ground.

Entry of the pilot drill pipe or string is often 12 degrees , pilot hole continues at a 12 degree angle until it passes to level out horizontally under the obstacle. Once the hole has passed obstacle it rises the far side with an 8 degrees.

Bentonite drilling mud is pumped down the centre of the drill rods. The drill head consists of either a jetting head or a drill bit.

Open cut•In a 1000’ long project, 12” pipe replacement• Export /import of soil = over 500 truck trips

Trenchless (Pipe Bursting)•In a 1000’ long project• Pits every 300 feet (25’x10’x10’)• Co-located at manholes• Export/import of soil = ~75 truck trips

LESS SOCIAL IMPACT

And Smaller Carbon Footprint

TRENCHLESS TECHNOLOGY: IN INDIA•Brihan Mumbai municipal corporation has used micro tunneling for the construction of 3m diameter tunnel.

•MTNL has installed large telephone cables of approximately 185 km length in Delhi & Kolkata by this method.

•Pipe line laying below river bed is impossible by open trench method, pipe line laying below Hoogly river by this technique is sufficient to say its importance.

•In Kolkata 700m length and 0.762 diameter iron pipe was repaired which started leakage.

•Laying of 18’ dia. Pipe of HBJ (Hazira-Bijaipur-Jagdishpur) across Yamuna river is accomplished by this technique.

•1719m gas pipeline was laid 35m below Godavari river in 1994.

•24’ diameter and 350 long pipes were successfully installed by Indian oil corporation for Panipat refinery.

Conclusion • By adopting this technology we can successfully

implement pipes under the surface without making any disruptions to the environment and public.This enables us to retain our available resources, thereby, keeping the earth unexcavated.

REFERENCES• “Trenchless Technology” by Mr. S.R NABEEL.• “Micro-tunneling Technology” by Mr. Shyamal Sarkar.• “Trenchless Repairing” by Woo Seok Chin, Jae Wook

Kwon, & Dai Gil Lee.• “Trenchless Technology Solutions” by Mr. Robert

Zlokovitz.• “Trenchless technology for rehabilitation of sewers” by

Alfred Angerlehner & Christian Dobretsberger.• “Summary of Trenchless Technology” by Rob Piehl.