بررسی عددی رفتار خاک متورم‌شونده‌ و تاثیر آن بر نیروهای داخلی غلاف چاه‌های گاز بر پایه‌ی مکانیک خاک غیراشباع، مطالعه موردی: خانگیران سرخس

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه مهندسی عمران، دانشکده مهندسی، دانشگاه فردوسی مشهد، مشهد، ایران

چکیده

اکثر طرح‌ها و پروژه‌های عمرانی بر روی خاک‌هایی بنا می‌شود که بالاتر از سطح آب زیرزمینی است و این امر موجب می‌شود که، خاک در فاز غیراشباع قرار گرفته و در آن مکش بافتی ایجاد شود. افزایش و یا کاهش درجه اشباع خاک، بر روی خواص مکانیکی و هیدرولیکی آن تاثیر بسیار زیادی می‌گذارد. خاک‌های متورم‌ شونده خاک‌هایی هستند که با جذب رطوبت و کاهش مکش بافتی، افزایش حجم از خود نشان می‌دهند. بنابراین، این موضوع خسارت‌های جبران ناپذیری را در صنعت ساخت و ساز، راهسازی و صنایعی از قبیل نفت و گاز به وجود میآورد. در این تحقیق خاک متورم‌شونده‌ی اطراف یکی از چاه‌های گاز خانگیران سرخس مورد بحث و تحلیل عددی قرار گرفته است. نتایج مدل‌سازی عددی نشان داد در نقطه‌ی بحرانی لوله‌ی فولادی بدنه‌ی چاه، نیروی کششی ناشی از تورم خاک به اطراف آن ‌ وارد می‌شود که ضخامت طراحی و مجاز لوله‌ی چاه برای تحمل این نیرو با استفاده از دو روش ضرایب بار، مقاومت و مقاومت مجاز به دست می‌آید. نتایج نشان داد ضخامت‌های به دست‌ آمده اعداد کوچکی هستند، در نتیجه خطری جدی ناشی از تورم خاک و ایجاد نیروی کششی بر بدنه-ی چاه مطرح نیست و اگر فولاد بدنه‌ی چاه در طول زمان دچار خوردگی‌های بسیار گسترده نشود، در اثر کشش ناشی از تورم خاک گسیخته نخواهد شد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Numerical investigation of swelling soil behavior and its effect on gas well casing internal forces based on unsaturated soil mechanics, case study: Khangiran, Sarakhs

نویسندگان [English]

  • Mehrab Balighi
  • Mohammad Saleh Baradaran
  • Ali Akhtarpour
Civil engineering faculty, Department of engineering, Ferdowsi University of Mashhad, Iran
چکیده [English]

The majority of building and infrastructure projects are typically situated on soils that have a greater elevation than the underlying water table. As a consequence, these soils exist in an unsaturated state, resulting in the development of matric suction inside them. The manipulation of soil saturation levels significantly influences its mechanical and hydraulic characteristics. Swelling soils refer to a type of soil that undergoes volumetric expansion as a result of moisture absorption and a subsequent decrease in matric suction. Hence, this matter gives rise to irreversible harm in the realm of infrastructure, transportation networks, and facilities such as oil and gas. This study focuses on the numerical analysis and discussion of the swelling soil surrounding a gas well located within the Khangiran gas refinery. The findings from the numerical simulation demonstrated that, at the critical juncture of the steel pipe within the well structure, the tensile force induced by soil expansion infiltrates the surrounding area. To withstand this force, the design and permissible thickness of the well pipe can be evaluated using two approaches: load coefficients-resistance and allowable resistance. The action is permissible. The findings indicate that the thicknesses obtained are relatively small, thereby suggesting that there is no significant risk associated with soil swelling and the resultant tensile force exerted on the well casing. However, it is important to note that the durability of the well body's steel material over time is crucial in preventing breakage due to soil swelling-induced tension.

کلیدواژه‌ها [English]

  • swelling soil
  • unsaturated soil mechanics
  • numerical modeling
  • Khangiran Sarakhs gas zone
  • gas well
  1. Chapman, Tim, Hilary Skinner, D. G. Toll, Kelvin Higgins, Mike Brown, and John Burland, eds. ICE Manual of Geotechnical Engineering Volume 2: Geotechnical design, construction and verification. Vol. 2. Emerald Group Publishing, 2023.
  2. Baradaran, Mohammad Saleh, Ramin Qazanfari, and Sajed Baradaran. “Study of soil reinforcement in the east of Mashhad using glass granule.” Materials Research Express 10, no. 5 (2023): 055202.
  3. Baradaran, Sajed, and Mahmoud Ameri. “Investigation of rutting failure in asphalt mixtures and its improvement strategies.” Road 31, no. 114 (2023): 53-70.
  4. Cui, Y. J., Ferrari, A., Gallipoli, D., Jommi, C., Laloui, L., Pirone, M., ... & Wheeler, S. Unsaturated soil mechanics. International Society of Soil Mechanics and Geotechnical Engineering, 2004.
  5. Huang, Runqiu, and W. U. Lizhou. “Stability analysis of unsaturated expansive soil slope.” Earth Science Frontiers 14, no. 6 (2007): 129-133.
  6. Avsar, Elif, Resat Ulusay, and Harun Sonmez. “Assessments of swelling anisotropy of Ankara clay.” Engineering Geology 105, no. 1-2 (2009): 24-31.
  7. Langroudi, Arya Assadi, and S. Shahaboddin Yasrobi. “A micro-mechanical approach to swelling behavior of unsaturated expansive clays under controlled drainage conditions.” Applied Clay Science 45, no. 1-2 (2009): 8-19.
  8. Liang, C. H. E. N., Zong-Ze Yin, and Pei Zhang. “Relationship of resistivity with water content and fissures of unsaturated expansive soils.” Journal of China University of Mining and Technology 17, no. 4 (2007): 537-540.
  9. Al-Yaqoub, Thamer H., Jafarali Parol, and Dobroslav Znidarcic. “Experimental investigation of volume change behavior of swelling soil.” Applied Clay Science 137 (2017): 22-29.
  10. Feng, Jun, and Guangze Zhang. “Study on soil water and suction stress characteristics for unsaturated no. 1 (1973): 97-104.
  11. United States. Bureau of Yards, and Docks. Building Maintenance: Structures. US Government Printing Office, 1963. McKeen, R. Gordon. Design of airport pavements for expansive soils. No. DOT/FAA/RD-81/25 Final Rpt. NTIS, 1981.
  12. Seed, H. Bolton, Richard J. Woodward Jr, and Raymond Lundgren. “Prediction of swelling potential for compacted clays.” Journal of the soil mechanics and foundations division 88, no. 3 (1962): 53-87.
  13. Aubertin, Michel, Jean-Francois Ricard, and Robert P. Chapuis. “Apredictivemodelforthewaterretentioncurve: application to tailings from hard-rock mines.” Canadian Geotechnical Journal 35, no. 1 (1998): 55-69.
  14. Van Genuchten, M. Th. “A closed‐form equation for predicting the hydraulic conductivity of unsaturated soils.” Soil science society of America journal 44, no. 5 (1980): 892-898.
  15. Chen, Yanyan, Yuanming Lai, Hongwei Li, and Wansheng Pei. “Finite element analysis of heat and mass transfer in unsaturated freezing soils: Formulation and verification.” Computers and Geotechnics 149 (2022): 104848.
  16. Karbalaee, AliReza, ZahraHedjazizadeh, andSeyedAbolfazl Masoodian. “Spatiotemporal variations of albedo using MODIS and PCA analysis in Iran.” Theoretical and Applied Climatology 145, no. 1 (2021): 245-260.
  17. Cheuk, C. Y., W. A. Take, M. D. Bolton, and J. R. M. S. Oliveira. “Soil restraint on buckling oil and gas pipelines buried in lumpy clay fill.” Engineering structures 29, no. 6 (2007): 973-982.
  18. Scanlon, Bridget R., Jean Phillippe Nicot, and Joel W. Massmann. “Soil gas movement in unsaturated systems.” Soil physics companion 389 (2002): 297-341.
  19. Nie, Zhen, Shuzhe Shi, Bohong Wu, and Xueqin Huang. “Axial Force Calculation Model for Completion String with Multiple Point Resistances in Horizontal Well.” Processes 11, no. 9 (2023): 2621.
  20. Fyrileiv, Olav, and Leif Collberg. “Influence of pressure in pipeline design: effective axial force.” In International Conference on Offshore Mechanics and Arctic Engineering, vol. 41979, pp. 629-636. 2005.