Numerical investigation of the engineering protection methods aimed to reduce the power of the heaving soils acting on underground pipelines

UDK: 624.131 621.644
DOI: 10.24887/0028-2448-2019-1-88-93
Key words: frost heave, waterproof bed, stress-strain state of the pipeline
Authors: E.V. Markov (Tyumen Industrial University, RF, Tyumen), S.A. Pulnikov (Tyumen Industrial University, RF, Tyumen)

The operational reliability of pipeline systems in the conditions of Western Siberia is determined mainly by the ability of the pipeline structure to provide an operational position under the influence of destructive geological processes within the limits of acceptable values. Frost heaving of soils is most dangerous process for “warm” and “cold” pipelines, which is associated with huge forces and small absolute deformations because it don’t allow well-time diagnosis in high snow cover and absent of a planned-high-altitude position monitoring system. To date, design solutions for engineering protection of pipelines against frost heaving do not provide a standard level of reliability, which makes the problem of increasing the efficiency of engineering protection more important.

The authors divided the engineering protection methods into two groups: the first group reduces the heaving properties of the soil; the second group reduces forces from the side of heaving soil. The article shows the results of the numerical study of engineering protection methods of the second group. Analysis of the results showed an increased danger of local frost heaving with a length of no more than 21 m for main pipelines with a diameter of 530 to 1420 mm in comparison with longer ones. It proves the necessity of using the engineering protection on the all distance from the well with heaving soil to the well with non-heaving soil. Reducing the restrained capacity of adjacent non heaving soils reduces the stress-strain state in heaving areas. However it increases the risks of emerging and arch formation in engineering and geological conditions of Western Siberia and is not recommended for use. The use of soil bedding made of non-heaving materials under the bottom of pipe to reduce the forces and displacements from frost heaving can significantly reduce the stress-strain state of the pipeline. The numerical study of the bedding geometric parameters, carried out by the authors of the article, showed that the bedding made of materials more rigid than the soil of the ground should be deeper, and less rigid should be wider, due to the difference in protective properties.

References

1. Lazarev S.A., Pul'nikov S.A., Sysoev Yu.S., Diagnosing of extended spatially deformed sections of gas pipelines in the technical state and the integrity management system of Gazprom PJSC (In Russ.), Territoriya NEFTEGAZ, 2016, no. 4, pp. 106–115.

2. Lazarev S.A., Pul'nikov S.A., Sysoev Yu.S., Evaluation of the technical condition of the linear part of main gas pipelines in the zones of significant spatial deformation (In Russ.), Gazovaya promyshlennost', 2016, no. 9 (743), pp. 84–90.

3. Aleskerova Z.Sh., Pul'nikov S.A., Sysoev Yu.S., Estimation categories and criteria of main gas pipelines geotechnical condition under dynamicof adverse climatic processes (In Russ.), Izvestiya vuzov. Neft' i gaz, 2016, no. 6, pp. 30–35.

4. Gorkovenko A.I., Osnovy teorii rascheta prostranstvennogo polozheniya podzemnogo truboprovoda pod vliyaniem sezonnykh protsessov (Fundamentals of the theory of calculating the spatial position of an underground pipeline under the influence of seasonal processes): thesis of doctor of technical science, Tyumen', 2006.

5. Ivanov I.A., Ekspluatatsionnaya nadezhnost' magistral'nykh truboprovodov v rayonakh glubokogo sezonnogo promerzaniya puchinstykh gruntov (Operational reliability of main pipelines in the areas of deep seasonal freezing of heaving soils): thesis of doctor of technical science,Tyumen', 2002.

6. Mikhaylov P.Yu., Dinamika teplomassoobmennykh protsessov i teplosilovogo vzaimodeystviya promerzayushchikh gruntov s podzemnym truboprovodom (Dynamics of heat and mass transfer processes and thermal power interaction of freezing soils with an underground pipeline): thesis of candidate of physical and mathematical science, Tyumen', 2012.

7. Chikishev V.M., Issledovanie protsessa silovogo vzaimodeystviya lineynoy chasti truboprovodov s promerzayushchim gruntom (The study of the process of force interaction of the linear part of pipelines with freezing soil): thesis of candidate of technical science,Tyumen', 1999.

8. Aybinder A.V., Raschet magistral'nykh i promyslovykh truboprovodov na prochnost' i ustoychivost' (Calculation of strength and stability for main and field pipelines), Moscow: Nedra Publ., 1991, 287 p.

9. Kiselev M.M., Calculation of the normal forces of frost buckling foundations (In Russ.), Osnovaniya, fundamenty i mekhanika gruntov, 1961, no. 5, pp. 23–24.

10. Puskov V.I., Raschet normal'nykh sil moroznogo pucheniya gruntov na podoshve zhestkoy polosy s ogranichennoy podatlivost'yu (Calculation of the normal forces of frost heaving of soils on the sole of a rigid strip with limited compliance), Proceedings of NIIZhT, 1967, V. 13, pp. 141–150.

11. Shvets V.B., Elyuvial'nye grunty Urala kak osnovaniya fundamentov zdaniy i sooruzheniy (Eluvial soils of the Urals as the base of the foundations of buildings and structures): thesis of doctor of technical science, Moscow, 1967, 51 р.

12. Kuznetsov A.O., Practical computation method of slopes reinforced by horizontal bars of round cross-section (In Russ.), Izvestiya VNII gidrotekhniki im. B.E. Vedeneeva, 2017, V. 283, pp. 88–96.

The operational reliability of pipeline systems in the conditions of Western Siberia is determined mainly by the ability of the pipeline structure to provide an operational position under the influence of destructive geological processes within the limits of acceptable values. Frost heaving of soils is most dangerous process for “warm” and “cold” pipelines, which is associated with huge forces and small absolute deformations because it don’t allow well-time diagnosis in high snow cover and absent of a planned-high-altitude position monitoring system. To date, design solutions for engineering protection of pipelines against frost heaving do not provide a standard level of reliability, which makes the problem of increasing the efficiency of engineering protection more important.

The authors divided the engineering protection methods into two groups: the first group reduces the heaving properties of the soil; the second group reduces forces from the side of heaving soil. The article shows the results of the numerical study of engineering protection methods of the second group. Analysis of the results showed an increased danger of local frost heaving with a length of no more than 21 m for main pipelines with a diameter of 530 to 1420 mm in comparison with longer ones. It proves the necessity of using the engineering protection on the all distance from the well with heaving soil to the well with non-heaving soil. Reducing the restrained capacity of adjacent non heaving soils reduces the stress-strain state in heaving areas. However it increases the risks of emerging and arch formation in engineering and geological conditions of Western Siberia and is not recommended for use. The use of soil bedding made of non-heaving materials under the bottom of pipe to reduce the forces and displacements from frost heaving can significantly reduce the stress-strain state of the pipeline. The numerical study of the bedding geometric parameters, carried out by the authors of the article, showed that the bedding made of materials more rigid than the soil of the ground should be deeper, and less rigid should be wider, due to the difference in protective properties.

References

1. Lazarev S.A., Pul'nikov S.A., Sysoev Yu.S., Diagnosing of extended spatially deformed sections of gas pipelines in the technical state and the integrity management system of Gazprom PJSC (In Russ.), Territoriya NEFTEGAZ, 2016, no. 4, pp. 106–115.

2. Lazarev S.A., Pul'nikov S.A., Sysoev Yu.S., Evaluation of the technical condition of the linear part of main gas pipelines in the zones of significant spatial deformation (In Russ.), Gazovaya promyshlennost', 2016, no. 9 (743), pp. 84–90.

3. Aleskerova Z.Sh., Pul'nikov S.A., Sysoev Yu.S., Estimation categories and criteria of main gas pipelines geotechnical condition under dynamicof adverse climatic processes (In Russ.), Izvestiya vuzov. Neft' i gaz, 2016, no. 6, pp. 30–35.

4. Gorkovenko A.I., Osnovy teorii rascheta prostranstvennogo polozheniya podzemnogo truboprovoda pod vliyaniem sezonnykh protsessov (Fundamentals of the theory of calculating the spatial position of an underground pipeline under the influence of seasonal processes): thesis of doctor of technical science, Tyumen', 2006.

5. Ivanov I.A., Ekspluatatsionnaya nadezhnost' magistral'nykh truboprovodov v rayonakh glubokogo sezonnogo promerzaniya puchinstykh gruntov (Operational reliability of main pipelines in the areas of deep seasonal freezing of heaving soils): thesis of doctor of technical science,Tyumen', 2002.

6. Mikhaylov P.Yu., Dinamika teplomassoobmennykh protsessov i teplosilovogo vzaimodeystviya promerzayushchikh gruntov s podzemnym truboprovodom (Dynamics of heat and mass transfer processes and thermal power interaction of freezing soils with an underground pipeline): thesis of candidate of physical and mathematical science, Tyumen', 2012.

7. Chikishev V.M., Issledovanie protsessa silovogo vzaimodeystviya lineynoy chasti truboprovodov s promerzayushchim gruntom (The study of the process of force interaction of the linear part of pipelines with freezing soil): thesis of candidate of technical science,Tyumen', 1999.

8. Aybinder A.V., Raschet magistral'nykh i promyslovykh truboprovodov na prochnost' i ustoychivost' (Calculation of strength and stability for main and field pipelines), Moscow: Nedra Publ., 1991, 287 p.

9. Kiselev M.M., Calculation of the normal forces of frost buckling foundations (In Russ.), Osnovaniya, fundamenty i mekhanika gruntov, 1961, no. 5, pp. 23–24.

10. Puskov V.I., Raschet normal'nykh sil moroznogo pucheniya gruntov na podoshve zhestkoy polosy s ogranichennoy podatlivost'yu (Calculation of the normal forces of frost heaving of soils on the sole of a rigid strip with limited compliance), Proceedings of NIIZhT, 1967, V. 13, pp. 141–150.

11. Shvets V.B., Elyuvial'nye grunty Urala kak osnovaniya fundamentov zdaniy i sooruzheniy (Eluvial soils of the Urals as the base of the foundations of buildings and structures): thesis of doctor of technical science, Moscow, 1967, 51 р.

12. Kuznetsov A.O., Practical computation method of slopes reinforced by horizontal bars of round cross-section (In Russ.), Izvestiya VNII gidrotekhniki im. B.E. Vedeneeva, 2017, V. 283, pp. 88–96.


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