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توسعه چارچوبی برای بررسی اثر پدیده فرونشست بر روی خطوط لوله و سطح بندی میزان آسیب، مطالعه موردی: دشت های غرب استان تهران
ستاری، نگین Sattari, Negin
Development of a Framework to Investigate the Effect of Subsidence Phenomenon on Pipelines and Classify the Extent of Damage, Case Study: Western Plains of Tehran Province
Sattari, Negin | 2025
38
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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 58679 (09)
- University: Sharif University of Technology
- Department: Civil Engineering
- Advisor(s): Raie, Mohammad
- Abstract:
- Land subsidence is the downward movement of the ground surface, which occurs mainly due to groundwater withdrawal and causes damage to infrastructure, including pipelines. In this study, the behavior of buried pipelines under the effect of land subsidence was investigated. First, using subsidence zoning maps, the areas under subsidence were identified and the amount of subsidence was determined. Then, using the finite element software OpenSees, the interaction between the pipeline and the soil was modeled using a spring, the amount of subsidence was applied to it, the values of the Von Mises stresses created in each element were calculated, and the stress leveling was performed. The results show that in elements where the difference in subsidence between the two ends of the element is greater, larger Von Mises stresses occur. Subsequently, a parametric study was conducted in 40 cases to investigate the effect of various factors on the Von Mises stresses caused by subsidence of the steel pipeline. These include pipeline diameter-to-thickness ratios of 22.7, 32, 42.7, 51, and 56, pipeline internal pressures of 30 and 60 bar, temperature changes over the pipeline installation time of 15 and -15°C, dense sandy soil with an internal friction angle of 40°, and soft clay with a cohesion of 20 kPa. The results of this study show that in the case of soft clay, internal pressure of 30 bar, and temperature difference of -15°C, with an increase in pipeline diameter-to-thickness ratio from 22.7 to 56, the ratio of Von Mises stresses to pipeline failure stress due to subsidence increased by 27%. Also, in the case of soft clay, the ratio of the pipeline diameter to thickness is 56 and the temperature difference is -15℃, with the increase of the internal pressure of the pipeline from 30 bar to 60 bar, the ratio of the Von Mises stresses to the pipeline failure stress due to subsidence increases by 32%. In addition, in the case of soft clay, the internal pressure is 30 bar and the ratio of the pipeline diameter to thickness is 56, with the decrease of the temperature during operation compared to the installation time of the pipeline by 15℃, the ratio of the Von Mises stresses to the pipeline failure stress due to subsidence increases by 20% compared to the increase of the temperature by 15℃. Also, in the case of the pipeline diameter to thickness ratio is 56, the temperature difference is -15℃ and the internal pressure is 30 bar, with the change of the soil type from soft clay to dense sand, the ratio of the Von Mises stresses to the pipeline failure stress due to subsidence increases by 1.25%. The results of this research can be used to modify existing pipelines or design future pipelines under the effect of subsidence
- Keywords:
- Land Subsidence ; Subsidence Phenomenon ; Buried Pipline ; Finite Element Method ; Parametric Study ; Pipelines ; Subsidence Zoning Map ; Subsidence Damage Leveling
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