Strength provision of the underground section of the oil pipeline in the karst zone when installing various types of compensators

UDK: 622.692.4
DOI: 10.24887/0028-2448-2018-3-82-84
Key words: stress, strain, strength, pipeline, project position
Authors: R.N. Bakhtisin (Ufa State Petroleum Technological University, RF, Ufa), R.M. Zaripov (Ufa State Petroleum Technological University, RF, Ufa), G.E. Korobkov (Ufa State Petroleum Technological University, RF, Ufa), R.B. Masalimov (Ufa State Petroleum Technological University, RF, Ufa)

This article is devoted to the study of the stress-strain state and the strength provision of the underground section of the oil pipeline in the karst zone with a design position violation when installing pipe compensators at the ends of the analyzed section and in its underground parts, specially designed to remove longitudinal compressive forces in the pipe wall. In the article the pipe is modeled by a rod system consisting of curved and straight tubular section rods. Stress-strain state calculations of the selected pipeline section in the karst zone were carried out for the following cases: 1) when its ends were jammed with soil; 2) when outlet compensators are installed on the ground surface in the place of the pipeline outlet; 3) when in the underground part of the pipeline compensator-supports (U-shaped) are installed, made up of standard bends with a radius of curvature of 35 meters and straight pipes; 4) in the place where the pipeline exits to the surface of the earth with its underground part compensator are installed. The results of the calculation are presented in the form of diagrams of the main characteristics of the stress-strain state of oil pipeline and in the form of tables where extreme values of these characteristics are given. Calculation revealed that the installation of compensator-supports leads to a decrease not only stress fr om the longitudinal force of the compression pipe in the underground part, wh ere the ground is weakened by the development of karst, but the extreme values of the bending stress and the maximum (fiber) total longitudinal stress. By calculation, the effective work of the oil pipeline with expansion joints in the underground part, compared to those considered in this article other designs in the pipeline. It was found out that in the presence of compensator-supports in its underground part the installation of compensators at the ends of the analyzed site proved to be not only ineffective, but even dangerous.

References

1. Aynbinder A.B., Kamershteyn A.G., Raschet magistral'nykh truboprovodov na prochnost' i ustoychivost' (Calculation of trunk pipelines for strength and stability), Moscow: Nedra Publ., 1982, 340 p.

2. SP 36.13330.2012. Trunk pipeline. Revised edition of SNiP 2.05.06-85*.

3. Shammazov A.M., Zaripov R.M., Chichelov V.A., Korobkov G.E., Raschet i obespechenie prochnosti truboprovodov v slozhnykh inzhenerno-geologicheskikh usloviyakh. Chislennoe modelirovanie napryazhenno-deformirovannogo sostoyaniya i ustoychivosti truboprovodov (Calculation and maintenance of strength of pipelines in complicated geotechnical conditions. Numerical modeling of stress-strain state and stability of pipelines), Part 1, Moscow: Inter Publ., 2005, 706 p.

4. Shammazov A.M., Zaripov R.M., Chichelov V.A., Korobkov G.E., Raschet i obespechenie prochnosti truboprovodov v slozhnykh inzhenerno-geologicheskikh usloviyakh. Chislennoe modelirovanie napryazhenno-deformirovannogo sostoyaniya i ustoychivosti truboprovodov (Calculation and maintenance of strength of pipelines in complicated geotechnical conditions. Numerical modeling of stress-strain state and stability of pipelines), Part 2, Moscow: Inter Publ., 2006, 564 p.

5. Korobkov G.E., Zaripov R.M., Shammazov I.A., Chislennoe modelirovanie napryazhenno-deformirovannogo sostoyaniya i ustoychivosti truboprovodov i rezervuarov v oslozhnennykh usloviyakh ekspluatatsii (Numerical modeling of stress-strain state and stability of pipelines and reservoirs in complicated operating conditions), St. Petersburg, Nedra Publ., 2009, 409 p.

This article is devoted to the study of the stress-strain state and the strength provision of the underground section of the oil pipeline in the karst zone with a design position violation when installing pipe compensators at the ends of the analyzed section and in its underground parts, specially designed to remove longitudinal compressive forces in the pipe wall. In the article the pipe is modeled by a rod system consisting of curved and straight tubular section rods. Stress-strain state calculations of the selected pipeline section in the karst zone were carried out for the following cases: 1) when its ends were jammed with soil; 2) when outlet compensators are installed on the ground surface in the place of the pipeline outlet; 3) when in the underground part of the pipeline compensator-supports (U-shaped) are installed, made up of standard bends with a radius of curvature of 35 meters and straight pipes; 4) in the place where the pipeline exits to the surface of the earth with its underground part compensator are installed. The results of the calculation are presented in the form of diagrams of the main characteristics of the stress-strain state of oil pipeline and in the form of tables where extreme values of these characteristics are given. Calculation revealed that the installation of compensator-supports leads to a decrease not only stress fr om the longitudinal force of the compression pipe in the underground part, wh ere the ground is weakened by the development of karst, but the extreme values of the bending stress and the maximum (fiber) total longitudinal stress. By calculation, the effective work of the oil pipeline with expansion joints in the underground part, compared to those considered in this article other designs in the pipeline. It was found out that in the presence of compensator-supports in its underground part the installation of compensators at the ends of the analyzed site proved to be not only ineffective, but even dangerous.

References

1. Aynbinder A.B., Kamershteyn A.G., Raschet magistral'nykh truboprovodov na prochnost' i ustoychivost' (Calculation of trunk pipelines for strength and stability), Moscow: Nedra Publ., 1982, 340 p.

2. SP 36.13330.2012. Trunk pipeline. Revised edition of SNiP 2.05.06-85*.

3. Shammazov A.M., Zaripov R.M., Chichelov V.A., Korobkov G.E., Raschet i obespechenie prochnosti truboprovodov v slozhnykh inzhenerno-geologicheskikh usloviyakh. Chislennoe modelirovanie napryazhenno-deformirovannogo sostoyaniya i ustoychivosti truboprovodov (Calculation and maintenance of strength of pipelines in complicated geotechnical conditions. Numerical modeling of stress-strain state and stability of pipelines), Part 1, Moscow: Inter Publ., 2005, 706 p.

4. Shammazov A.M., Zaripov R.M., Chichelov V.A., Korobkov G.E., Raschet i obespechenie prochnosti truboprovodov v slozhnykh inzhenerno-geologicheskikh usloviyakh. Chislennoe modelirovanie napryazhenno-deformirovannogo sostoyaniya i ustoychivosti truboprovodov (Calculation and maintenance of strength of pipelines in complicated geotechnical conditions. Numerical modeling of stress-strain state and stability of pipelines), Part 2, Moscow: Inter Publ., 2006, 564 p.

5. Korobkov G.E., Zaripov R.M., Shammazov I.A., Chislennoe modelirovanie napryazhenno-deformirovannogo sostoyaniya i ustoychivosti truboprovodov i rezervuarov v oslozhnennykh usloviyakh ekspluatatsii (Numerical modeling of stress-strain state and stability of pipelines and reservoirs in complicated operating conditions), St. Petersburg, Nedra Publ., 2009, 409 p.


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