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Directional Drilling Machines |
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Trenchless Technology: As the global search for sustainable development and environment friendly technologies intensifies, Trenchless Technology has begun to gain more and more ground. International conferences and seminars are being held to make engineers aware of this smooth and clean technique. On the engineers agenda is 24th International no dig 2006 conference and exhibition to be held in Queensland, Australia in October-November, 2006. In India, Indian Society for Trenchless Technology with the slogan ‘No Dig India’ has come up. Not only this, a Post Graduate Diploma for Trenchless Pipe line Manager has been started. All these developments are strong indicators of Trenchless Technology becoming popular in the days to come.
As the name suggests, it is the technology that allows laying of pipes or cables along or under the roads without disturbing the road surface. The work continues below ground while the traffic runs as usual. Digging out trenches for laying pipe-lines or cables along or under the roads already open to traffic is a nuisance –making exercise but an unavoidable part of construction jobs. The traffic gets diverted leading to frequent jams and impatient blaring of horns. In most of the cases, the back-filling of soil after the laying of pipes or cables is not done in a proper manner. Resultant pits and bumps make the vehicles jump and leave the drivers cursing under their breath. Even the cool breeze gets laced with the dust left on the roads. In nut-shell, the journey doesn’t remain a pleasant one.
Directional Drilling Machines : Trenchless laying of pipes and cables has become possible due to the availability of Directional Drilling Machines. A DDM consists of a boring unit, an electronic tracking equipment and a drill component. The pull force, torque and pump pressure of the boring rig depend upon the soil strata through which the pipe or cable is to pass, the diameter of the pipe or cable and its depth below the ground. Unforeseen increases in pull load due to ground conditions are also taken into account. The electronic tracking equipment enhances the trencher’s ability by automatically adjusting track speed and force with respect to ground conditions. An electric stroke limiter increases control and doesn’t allow the engine to stall whenever tough conditions are encountered. The machine operates at low speed and high torque. This helps the cutting bit to penetrate even the toughest rocks. Numerous boom options are available with different types of cutters and drill-bits. Right choice can be made depending upon the job to be handled.
How a DDM works: Driven pneumatically or hydraulically, DDMs drive a soil-displacement-hammer through the soil and toe the pipe or cable along the underground bore thus created. The hammer has a moving chisel head that makes its way through the soil along the designed alignment. A small pit is required at the point of commencement of laying the pipe-line or cable. This is called launching pit. The Directional Drilling Machine begins its work from this pit. Similarly an exit pit is required at the point of termination of cable or pipe. The entry angle and exit angle of the pipe or cable are carefully decided keeping the stress parameters and bending radius in view.
Production & Availability of DDMs : Some International firms are producing machines of different sizes, equipped with a variety of hammers and bits. Choice of hammer is decided with respect to the type of job, quantum of work and the working conditions i.e. whether a fluid or drilling medium can be used or dry conditions are to be maintained. Sensing the great potential in Trenchless technology, Indian manufacturers are also taking up production of directional drilling machines. Vermeer manufacturing company, USA, manufacturing quality DDMs has set up its office in Ajmer, Rajasthan. This firm produces DDMs that operate in narrow areas where space is a constraint. One company in India has already set up a large unit in Rajasthan and is now producing such machines of different capacities.
Laying cables and pipes: Cables and pipes of polyethylene or steel of diameter varying from 75 mm to 2 metre can be laid below ground, rivers, canals, roads and buildings using DDMs. For laying PVC pipes, a soil displacement hammer is utilized. When a steel pipe is to be laid, a steel pipe ramming hammer is used. Underground drilling can be done even through a solid rock. Not only the laying of new pipes and cables but replacement of existing but damaged pipelines laid for supply of water or gas or to discharge sewage can also be done by this technology and that too without digging these pipes out. For this, heavy duty steel rods of 3 feet length are thrust into the old pipe until these create a full string of rods. A force is then applied to fracture old pipe into small pieces. The machine also toes along a new pipe which keeps on occupying the position of old pipe being broken. Thus the dismantling of old pipe and laying of new pipe is done as a single activity. This brings savings in time and money. The areas which can be immensely benefited by Directional Drilling Machines are:
1. Water supply and Sewerage line laying.
2. Gas pipeline laying.
3. Telecom cable laying.
4. Electricity cable laying.
Pre-Conditions for using DDMs:
1. Soil Investigation: It is important to carry out soil investigations of the area to be drilled before a job is taken in hand. The soil strata and individual physical properties of each stratum, the particle size distribution curve and the position of water table are important to be known. Cone penetrometer test to find out the detail of erratic soft clay deposits should also be done. In case of rivers, the scour level needs to be known. The entry and exit angles are to be decided after these studies are completed. In most cases, these angles are kept between 6 degree and 15 degree. The minimum bending radius, the drill-trace-axis, the distance between entry or exit point and the obstacle such as river to be crossed are also decided after these studies.
2. Raising Necessary permits: Where required, necessary permits may have to be obtained from the River authority, Buildings & Roads department, Pollution control department and individuals before a job is taken in hand. Some traffic diversions may sometimes be felt necessary. Cutting of some trees along the alignment may be required as their roots might be interfering with the boring plan. For this, forest department may come in to picture. A drawing of the work area showing location of drilling machine, method of anchoring it, setting of drill fluid preparation unit, storage of pipes or cables to be laid, office cabin, generator and entry pit needs to be prepared before starting a big job.
Project planning: Before the project is executed, meticulous planning should be made in all civil engineering projects. While using a Directional Drilling machine, Project Planning should include applying thought process on the following important steps:
1. Soil investigations and surveying.
2. Selecting and preparing rig site.
3. Method of anchoring the machine.
4. Mobilizing crew and equipment.
5. Fabrication of pulling head.
6. Drill fluid arrangements.
7. Drilling operation.
8. Cutting off pulling head.
9. Restoring ground to original finish.
Project execution : To run a machine, generally a crew of two to three persons is sufficient. One person acts as the boring operator, one as the track equipment operator and third, if required, helps these two in carrying out their activities. Drill fluid is an essential requirement of all drilling operations. Normally, it consists of a suspension of water and bentonite. It makes the job of hydraulic cutting with the jet easier and stabilizes the bore hole, avoiding its collapse. Bentonite is a sort of clay having high contents of silica and alumina. Addition of the drilling fluid is regulated carefully as over release of it may rather hamper the operation besides wastage of fluid. Noise is low when the machine is working and the vibrations are minimal. In case of working below a road, the overhead traffic doesn’t come to know that a pipe or cable laying operation is going on below the ground.
Indian scene : Many companies in India have procured Directional drilling machines and are handling jobs in India and abroad. Some examples of the jobs handled in India are crossing a 400 metre wide and 15 metre deep river in Thane near Mumbai, having hard rock strata at its base and laying three layer polyethylene coated pipes of 450mm diameter, 10 metre below the base of the river. Two more examples of such jobs completed in West Bengal are the laying of 457mm dia HDPE conduits imported from China below river Harohar and river Rupnarayan crossing more than 350 metre length in each case. In New Delhi, the cabling work is now done by MTNL using Trenchless Technology. As this technique has the advantages of non-disruption of traffic, working in restricted area and as it is clean and non-destructive, it is fast becoming popular in India.
Machinery Available:
1. Vermeer Corp USA Directional Drilling Machine D7 x 11A Navigator2. Vermeer Corp USA Directional Drilling Machine, D16 x 20A Navigator3. Terra Macs Ltd. Auckland New Zealand Horizontal Directional Drilling Machine TX 150 B4. Terra Macs Ltd. Auckland New Zealand Horizontal Directional Drilling Machine, Mighty Mac5. Ditch Witch USA Jet Trac Mach1 Horizontal Directional Drilling Machine6. ASTEC USA DD-8 Horizontal Directional Drilling Machine7. ASTEC USA DD-6 Horizontal Directional Drilling Machine8. ASTEC USA DD-3238 Horizontal Directional Drilling Machine9. ASTEC USA DD-1215 Horizontal Directional Drilling MachineNote : Vermeer has stepped in India and opened an unit in Ajmer, Rajasthan under the name, Bharat Underground & Environment Equipment Company.
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Tip of the Moment
Always construct a basement when the water table (underground water level) is at its lowest.
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