TRENCHLESS TECHNOLOGY

CONTENTS INTRODUCTION TRENCHLESS TECHNOLOGY METHODS PRE-REQUISITES TECHNIQUES OF TRENCIILESS

TECHNOLOGY IN INDIA NEED FOR TRENCILESS TECHNOLOGY CONCLUSION REFERENCES

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. 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.

TRENCHLESS TECHNOLOGY METHODS

Trenchless technology methods system have been categorized in to two groups:1) New installation 2) Rehabilitation and Renovation 

NEW INSTALLATION

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

1) Microtunelling 2) Horizontal directional drilling 

REHABILITATION AND RENOVATION

Methods including are:

1) Pipe bursting2) Pipe eating

PRE-REQUISITES

Surveys and site investigations are essential to the success and efficiency of trench less installations and repair techniques.(a) The survey results help to determine the most appropriate systems.(b) The investigations methods include geophysical surveys, boring and sampling, measurement of ground water table, test pits and trenches, penetration tests, examinations and investigations of existing structures.

TECHNIQUES OF TRENCHLESS TECHNOLOGY IN INDIA

DIRECTIONAL DRILLING RAMMING MOLING AUGER BORING

DIRECTIONAL DRILLING

Directional drilling involves steerable tunnelling systems for both small and diameter lines. The first stage consists of drilling a small diameter pilot hole along the desired centre line of a proposed line and 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

Advantages

The major advantage is the speed of installation combined with the minimum environmental and social impact.

Long and complicated crossings can be accomplished with a great degree of accuracy.

Another advantage is that sufficient depth can be accomplished to avoid other utilities.

Limitation of access and reception pits is another advantage.

Disadvantages

Special equipment and very high degree of operation skill is required.

As the cost of the equipment and the operation are high, bore length should be sufficient in order for it to be economical.

Mainly steel pipe is being installed by the method.

RAMMING

In this method, the pipe is rammed through the soil by using a device attached to the end of the pipe to drive the pipe through the soil. In this method, the tool does not create a borehole. It acts as a hammer to drive the pipe through the soil. When ramming pipe, the leading edge cuts a borehole, the spoil enters the pipe and is compacted as it is being forced to the rear of the pipe.

RAMMING DEVICE

Advantages

The pipe ramming is an effective method for installing medium size pipes.

The method is economic since the equipment cost is not very high and the operation is simple.

The pipe can be installed in one piece or segments. This can be used in almost all types of soils. The method does not require any thrust reaction

structure.

Disadvantages

The major disadvantage is that there is no control over the line and grade and in case of obstructions like boulders, the pipe may be deflected.

Then work should be stopped immediately. For small diameter pipelines, the method is

economical, but for large diameter pipes, the equipment cost is high.

MOLING

Moling is a method, which forms the borehole by compressing the earth that immediately surrounds the compacting device which is an underground piercing (mole) is propelled by a power source. The tool is streamlined into bullet or shape. The method is restricted to relatively small diameter lines in compressible soil conditions.

MOLING DEVICE

Advantages

It is a rapid, economic, and effective method of installing small diameter lines.

Any type of utility line can be installed using the method.

The stability of the soil around the borehole is increased due to compaction.

The investment in equipment is minimum.

Disadvantages

Compaction methods are limited in their length by reliability because basic systems are unintelligent, unguided tools that tend to bury themselves, surface in the middle road or damage existing utility lines.

AUGER BORING

The auger horizontal earth boring is a process of simultaneously jacking casing through the earth while removing the spoil inside the casing by means of a rotating flight auger. The auger is a flighted tube having dual functions, firstly it has couplings at each end that transmit torque to the cutting head from the power source located in the bore pit and secondly, it serves to transfer spoil back to the machine.

AUGER BORING DEVICE

Advantages

The major advantage is that the casing is installed at the same time as the borehole excavation takes place.

This method can be used in a wide variety of soil types.

Disadvantages

This method requires different sized cutting heads and auger sizes or each casing diameter, which increases the investment in equipment.

The investment in bore, pit construction, and the initial setup is also required.

In case of soils containing large boulders, this method cannot be used advantageously.

NEED FOR TRENCHLESS TECHNOLOGY

(1) The disadvantages and difficulties encountered in conventional trenching methods have resulted in thinking of the need for trenchless technology.(2) The advantages of the no-dig technology are also responsible for the need of this technology to be adopted in mainly urban areas

CONCLUSION

With all round developments in various fields like petrochemicals where conveyance of gas, crude and refined products over long distances is common, telecommunication and power, water supply and sewerage etc.

Also if costs benefit analysis of the two systems is conducted, considering both direct and indirect costs, it will help us make informed divisions on technology selection, under different circumstances.

REFERENCES

1) Jagadish Chandra, Trenchless Technology in India: Need of the New Millennium. Civil Engineering and Construction Review October 2000- page 482) Maninder Singh, Techniques of Trenchless Technology In Use In India. Civil Engineering and Construction Review October 200- page 433) Dr.Neeraja Lugani Sethi, Pre- Requisites for Trenchless Technology. Civil Engineering and Construction Review October 2000- page 21