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

Document Type : Research Article

Authors

1 Civil engineering faculty, Department of engineering, Ferdowsi University of Mashhad, Iran

2 Department of Civil Engineering, Ferdowsi university of Mashhad, Iran

3 Civil Engineering Department, Engineering Faculty, ferodwsi University of Mashhad,Mashhad, Iran

Abstract

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.

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Amirkabir Journal of Civil Engineering

Articles in Press, Accepted Manuscript
Available Online from 04 July 2024

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