Trenchless Pipeline Management

Aug 17, 2006

Urban lifelines are the assets of the society and trenchless techniques provide avenues for Management of such assets which otherwise are being left neglected and deteriorating rapidly. Urban pipelines, when conceived, were meant to provide passage to fluids like water, rain runoff, sewage, petroleum, or other energy products. Primary consideration of employing a pipeline for such transportation has been that such mode yields the most economic and viable as the fluid flowing through them is not exposed anywhere and therefore there would be very slim chances of it getting polluted or polluting the environment en route to the intended destination.

As long as the pipeline is above ground or exposed, the networks meet these aims as any leakage or damage can be rectified immediately upon detection. But in urban settings, the pipelines are seldom above ground and damage rectifications are comparatively difficult since the detections are normally very late and at times rectifications are impossible due to extensive damages. Trenchless Techniques offer solutions for such difficult situations through which such rectification processes can be executed successfully.
Flow generation

Initially let us talk about the actions within the fluid conduits. The conduit provides a continuous passage so that the intended fluid moves freely and reaches the destination. This in turn means that the fluid must have enough pressure so as to reach such locations. In pressure mains or distributaries such pressure is provided by pumping in contrast the gravity flow lines develop pressures by slopes alone. Whatever may be the type of pipeline, the pressure needed to assist fluid to flow should be sufficient so that the fluid is able to overcome the pipeline surface friction and the retardations due to elevation changes.
A pressure less than such pressure requirements will result into flow stagnation or sluggish flow. A higher pressure will lead to several anomalies ranging from wastage of energy to the internal damages to the pipelines to major pipeline bursts. Optimum pressure evaluations are normally done by using any of the several methods like Manning's, or Darcy-Weisbach's, or Hazen-William's where such methods provide the possible head losses on the basis of flows, pipe surface frictions, pipe length etc.
For example as per Manning's formula the value of head loss is directly proportional to the length of pipeline, and the square of the flow velocity. It is also inversely proportional to hydraulic mean depth of pipe. Now if we expand the last paragraph it means that if a pipeline is leaking, or siltation has taken place, or pipeline surfaces have corroded substantially, the flow velocity will fall leading ultimately to a increased head loss and a requirement of additional head to balance this loss.
Impact of hydraulic mean depth over the head loss grows as it goes up substantially with the pipe deformation (the first stage of pipe collapse). Hydraulic mean depth in circular pipes is defined as the ratio of the area of cross section and the perimeter of the area. With the increase of the perimeter mean depth will go down leading to increase of the head loss.
As both of these will occur with the passage of time and earlier there were almost no ways to rehabilitate pipelines from inside (especially of smaller diameter where man entry was not possible) the basic approach used to be to assume a higher values of the coefficients like Manning's 'n' or 'e' of Darcy-Weisbach's formula or a lower value of CH in Hazen-William's formula while evaluating the possible head loss in older pipes. With the present day energy and resources starved society one cannot afford such higher safety factors and therefore the need is to prevent deterioration rather than enhancing head pressure to cover such head losses. In such situations trenchless rehabilitation techniques naturally come handy as we shall be discussing later.
Pipeline Design

Designing a pipeline calls for evaluating the required optimum pipe size including plate thickness jointing materials and their strength including interference avoidance. Sizing operations are dependent upon evaluating the applied stresses and selecting a section strong enough to take such stress without failure. In conventionally laid pipelines the pipe sections are assumed to withstand the following forces/stresses:
  • Internal fluid pressure;
  • Fluid hammer pressure;
  • Flexural stresses;
  • Stresses due to external loadings;
  • Temperature stresses;
  • Longitudinal stresses due to direction changes;
  • Stresses due to Torsion loading.
Situations, however, change when a trenchless installation is being executed. In such projects the pipe sections are either pulled, as in HDD method or pipe bursting, or jacked, as in pipe jacking projects, or rammed as in pipe ramming. In each of these operations the erection and installation forces may be the highest forces which that section might have been subjected during its entire life span as the pipeline portion.
For example, while pulling a pipe string through a mixed soil strata by HDD method the frictional forces on the pipe surface have to be overcome by the pullback force of the rig. The situation however has several more variables like the viscosity of the drilling fluid which reduces these frictional forces.
In contrast, when we are jacking a pipe direction of such forces reverses. A pipe under HDD can split in rupture whereas a jacking pipe can be crushed due to the compressive forces applied from the jacks. Pipe ramming in contrast operates on the concept of hammering where the impacting tool applies forces in shape of successive blows with minor intervals. Here although the rigidity of pipe is important, a more important quality of ramming pipes has to be its elasticity as the pipe has to take back its shape during the intervals. If not the fatigue of the pipe will lead to a complete deformation and failure of pipe at times.
The obvious corollary is that any pipe being used as a trenchless pipe needs to be sized, designed, and prepared to withstand these stresses. Needless to mention pipes good for one type of application may be completely failure in another application and therefore a detailed design process is important.
Pipeline materials

As outlined in the previous section pipelines are to be selected, sized, designed, and fabricated as per the end requirements as well as the erection and installation conditions. Material selection therefore is a part of pipeline design and for Trenchless application it is one of the most important activities in designs as any failure of pipeline due to material failure leads to complete network failure. The common pipeline materials can be classified under the following groups and subsequent subgroups:
  • Multi component Materials
    • Composite Construction
      • Concrete
      • Polyester Resin Concrete
    • Polyester Resin Concrete
      • Reinforced Concrete
      • Prestressed
    • Strengthened
      • Steel fibre concrete
      • Fibre cement
      • Glass reinforced plastic
  • Non-metallic inorganic
    • Vitrified clay
    • Bast bassalt
  • Metallic
    • Steel
    • Ductile iron
    • Cast iron
  • Organic
    • Polyethylene, PE-X
    • Polypropylene
    • Poly vinyl chloride-U
Pipelines need to have the least roughness of the internal pipe walls, the pipe and their joints should be free from visible defects, material must be resistant to corrosion, abrasion, and jetting stresses in addition to meeting strength requirements as discussed in the previous sections.
Added to the basic requirements trenchless applications call for specific qualities like elasticity, rigidity, toughness, or tightness with respect to materials and special joints, load/thrust bearing capacity, and dimensional stability with respect to pipe installation requirements. A detailed design naturally is a major requirement for pipeline management.
Geotechnical Surprise Avoidance

The next unforeseen part is the geotechnical surprises. These surprises are dealt under geotechnology, which is a branch of civil engineering concerned with soil or rock as a subsoil and structural material and with the means for investigating its condition and structural utility for construction and functional structures.
Trenchless projects call for executions with the least or minimal excavations. Naturally at most locations drilling/pushing/jacking would be occurring below the ground surfaces without any visual information on the ground level. Any surprise occurring at the drilling level would lead to the project failure and to ward this off, one need to have the best possible information which is collected through geotechnology.
Under this field the engineer employing geoscientific investigation methods and principles evaluates the rock and soil condition which affect site selection, method selection, enabling structures, pipeline material and other related precautions etc. The limiting geotechnical conditions help deciding in a suitable technology selection. The results of these investigations should be able to determine the stability of the excavation face, ease of fragmentation and transportability of subsoil material, presence of foreign structures or subsoil water bodies in the pipeline path, resistance to the signal transmission (radio or other waves), and soil deformations apart from other possible results.
Pipeline development and management activities naturally have a share of geotechnical studies and interpretation. The aspect assumes significance in case of Trenchless applications as generally it is too late to change a method after the equipment has entered the ground and surprises is one thing that no trenchless technologist should like at any cost.
Trenchless renovation and renewal

Developing an asset is only one part of pipeline management; renovation and renewal are two major portions of pipeline management activities without which the job of a Manager is incomplete. These activities are undertaken to replace, rehabilitate, upgrade or renovate a pipeline to provide a new economic life to an old pipeline. Management of subsurface networks of smaller diameters requires application of trenchless techniques in a major way and therefore the knowledge of these techniques is an imperative tool for pipeline managers.
Pertinent issues to be considered are the behaviour of pipelines under real time static and dynamic loadings; under impact loading; under rehabilitation process loading or under renewal process loading.
The ultimate goals of engineering of rehabilitation or renewal of pipelines are process optimization and usage economization of scarce and expensive resources while realizing the best possible output under a given situation and end conditions. The impediments however are the low levels of sensitization of engineers about such techniques. Either trenchless techniques are not used or in some cases a good technique remains unexplored and a partially unsuitable working technique is used for such projects. Net result is either an unsatisfactory project or waste of resources. Both of which are completely undesirable.
A structured learning of these techniques therefore is quite important for the Pipeline managers so that they are able to apply this knowledge to their activities and execute an optimum project.
Trenchless Pipeline Manager

With the above background the Indian Society for Trenchless Technology (IndSTT) has entered into an understanding with Kielce University of Technology, Faculty of Civil & Environmental Engineering, Poland (KUT) for imparting technical training in trenchless sector leading to award of a diploma titled as Trenchless Pipeline Manager (TPM) being awarded jointly by KUT and IndSTT.
The Kielce University of Technology is a fully academic institution, which offers bachelor's, master's and doctoral programmes. Gaining the right to habilitation in two disciplines has contributed to the development of the university's academic staff, providing them with an opportunity to apply for scientific degrees and titles. Presently, the University employs 833 staff, including 403 academic teachers.
Located on a 22-hectare campus in the city centre, the university's facilities comprise four teaching halls, the country-unique Centre for Laser Technologies of Metals, a modern building of the Main Library, six student houses, a hotel and a large building housing a canteen and recreation rooms.
IndSTT is the apex organization to promote the application of Trenchless Technology in India and South Asian region. As the demand for trained manpower for Trenchless applications is on rise and the available training facilities in the region are unavailable, IndSTT has entered into this understanding with KUT for necessary capacity building. In this training, following topics are to be covered:
  • Microtunnelling and pipe jacking
  • Horizontal directional drilling (HDD)
  • Impact moling and ramming
  • Optimum choice of trenchless pipe laying methods
  • Pipes in trenchless pipe laying technologies (jacking pipes and pulling in pipes)
  • Designing of pipelines for trenchless pipe laying
  • Trenchless renovation and replacement of pipelines
  • CCTV inspection of pipelines
  • Inspections and renovation of sewer collectors of large diameter
  • Trenchless repair and sealing of pipelines
  • Trends in the range of trenchless technology application
  • Static strength calculations of the pipelines
  • Strategies of trenchless renewal of sewerage and water supply pipelines
  • Design of the construction of renovation coatings
  • Plastics in underground infrastructure
  • Laboratory testings of pipes
  • Trenchless methods of cable laying
  • Structural expertises of pipelines
  • Trenchless testings of pipelines
  • Pipes made of rigid and elastic structure
  • Criteria of optimum choice of material and structural solutions of pipelines
  • Chosen problems of geotechnical engineering
  • Utility tunnels
To undergo this training, the participant must be an engineer (i.e. having a bachelor's degree in Civil/Public Health or Environmental Engineering or Mechanical or Electrical or an equivalent qualification). He or she must be conversant with written and spoken English. Preference would be given to persons with Environmental Engineering background or hands-on Trenchless Project Experience.
Course duration is of 120 hours being a combination of classroom training and practical exercises delivered at Kielce, Poland and other locations there. The duration of training is 1 month during which the trainees will be based in Kielce, Poland at the Technical University and shall live in the shared hall of residences of the university.
The first batch of training is scheduled to be held during September, 2006 and the maximum strength possible is 35 trainees.
Conclusion

Today's a large portion of subsurface utility network development and management activities in India and other South Asian nations are devoid of trenchless applications. An optimization of processes and economization of scarce resources can be successfully achieved if trenchless techniques are also considered in the technique selection process.
Such activity, however, can be undertaken if the executing engineer or the decision maker is abreast of such techniques and their selection processes. Such knowledge can be acquired by detailed classroom training and related workshop exposure. Trenchless Pipeline Manager is one such training planned by IndSTT and KUT.
Trenchless Pipeline Manager Certificate course is structured to address the requirements of subsurface utility pipeline construction which include development and management of networks. The trained engineers are expected to be able to engineer, design, supervise the construction, manage and maintain the subsurface pipelines successfully. The course is being developed by KUT jointly with IndSTT and is expected to be a major tool for capacity building in the Trenchless Technology Sector of South Asian Construction Industry.

Contact

Niranjan Swarup [Executive Director of the Indian Society for Trenchless Technology (INDSTT)]

110 019 New Delhi, India

Phone:

+91 11 4161 7862

Fax:

+91 11 4161 7863

E-Mail:

indstt@indstt.org

Internet:

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