Emergency hazard in main pipelines keeps growing with every year, especially in those that have been operated as long as over 15-20 years. What is the cause of imminent threats?

1. Regulatory documents for surveying and designing of main pipelines and capital structures for maintenance of the latter strongly advise to locate these projects on barren land (gullies, ravines, swamped areas etc.). There has been an erroneous opinion about “preservation” of fertile land.
2. Regulatory documents did not take a full account of regional geodynamic processes of the massifs on which structures have been built and are operated.
3. Such concepts as “geodynamic”, “microgeodynamic” zones (“zones of risk”) GDZ, activity of tectonic faults were known to a narrow circle of experts only.

UkrNTEC’s experience of many years in studying the causes of stability loss of industrial and civil structures, dikes (dams) of water reservoirs and slurry ponds, natural slopes of ravine and gully systems, opencast (mine) flanks has however showed that geodynamic processes in massifs are the major cause of stability loss.

In operation of main pipelines there are often observed unconventional types of corrosion. The mechanism of special types of corrosion is not yet clear.

Experts in electrolytic protection of underground structures indicate that mechanical stresses have a specific impact on the above corrosion, without revealing their nature:

• “Specific types of corrosion that result in drastic and often unpredictable changes in operating properties of structures are the most dangerous ones, their consequences can not be prevented by employing standard systems of electrolytic protection. These mainly include galvanic corrosion, corrosion and mechanical failure (corrosion cracking, corrosion “fatigue”, hydrogen embrittlement, corrosion and erosion failure” [E.Y. Liublinsky, 1987].
• “Mechanical stresses caused by operating conditions of underground structures can result in enhanced corrosion due to formation of corrosion elements on surface sections of structures, subjected to various mechanical stresses” [A.M. Zinevych et al., 1975].

“The sections under a great mechanical stress act then as anodes and get corroded more intensively. Periodic changes in mechanical stresses can change the conditions of the contact “structure-soil” and result in cracking of pipe walls” [A.M. Zinevich et al., 1975].

Our experience in assessing the impact of geodynamic processes of the geological environment on stability of overland structures as well as main oil and ammonia pipelines of Ukraine with the help of geological and geophysical methods has yielded the following concept, revealing major causes of specific types of corrosion of main pipelines:

1. Main pipelines cross blocks of rock massifs all the way along, which contact with each other through geodynamic zones (GDZ, micro GDZ, zones of risk) with a width ranging from tens to hundreds of meters as well as tectonic faults with different geodynamic activity.
2. In case of regular activation of tectonic faults, ground surface blocks shift by 5-10 mm (Fig. 1). Motions of rock and the evolving gases CH₄, Rn, H, Hq, CO₂ and others lead not only to a corrosion and mechanical failure of protective coatings but also to crack propagation in the pipe material.

Analogous processes run in GDZ and GDZ intersection points with lower intensity.

3. Industrial and civil structures for maintenance of main pipelines, that have been built on GDZ, GDZ intersection points and tectonic faults with no special foundations, tend to lose stability with time and collapse.
4. The soil on ravine and gully slopes is predisposed to slipping towards talwegs due to natural causes (Fig. 2).

Flooding of the slope soil activates slip processes and enhance the probability of soil slip.

Corrosion and mechanical failure of pipeline protective coatings and crack propagation in pipes make slope sections of pipeline routes particularly hazardous areas in terms of occurrence and development of technogenic and ecological emergencies.

5. Workings (opencasts, quarries, mines), located near main pipelines, adversely affect the latter – rock motion and other factors activate a corrosion and mechanical failure of pipelines.

Laying-up of mines dramatically enhances the probability of emergencies in main pipelines, located above workings, due to the buoyancy force action.

6. Flooding of main pipeline maintenance sites takes place along GDZ and tectonic faults. But the operation site location has been as a rule selected disregarding geodynamic parameters of massifs.
7. Latent long-distance migration of petroleum and its products at the level of underground water of the first water-bearing horizon usually proceeds along GDZ and tectonic faults.

1. Probability of “sudden” natural and technogenic emergencies in existing main pipelines on the territory of Ukraine keeps growing with every year as a result of disregarded geodynamic processes of massifs.
2. To prevent “sudden” natural and technogenic emergencies, it is essential to have information on evident manifestations of geodynamic processes along the whole main pipeline route.
3. A map of engineering and geodynamic zoning (a reconnaissance map) would provide the primary information on the massif geodynamic state along the whole route. Said map is drawn on the basis of a geological and geomorphologic analysis of the route topographic base, aerospace survey interpretation, analysis of geological fund materials as well as results of determination of operating properties of main pipeline protective coatings by the electrolytic protection control services.
4. In the second stage the hazardous and particularly hazardous sections identified in the first stage are explored with the help of field geophysical methods and detailed maps are drawn.
5. Environmentally successful operation of main pipelines would be ensured by combined efforts of surveyors, designers, pipeline operating staff and scientists – geologists and geophysicists.
6. Results of such exploration shall become the basis for introduction of appropriate alterations and amendments into regulatory documents.