Structural Behavior of Pipelines Buried in Expansive Soils under Rainfall Infiltration (Part I: Transverse Behavior)

Mohammed Bouatia,Zohra Derriche,Rafik Demagh

doi:10.28991/cej-2020-03091585

Abstract

Landslides, fault movements as well as shrink/swell soil displacements can exert important additional loadings on soil buried structures such as pipelines. These loadings may damage the buried structures whenever they reach the strength limits of the structure material. This paper presents a two-dimensional plane-strain finite element analysis of an 800 mm diameter water supply pipeline buried within the expansive clay of the Ain-Tine area (Mila, Algeria), considering the unsaturated behavior of the soil under a rainfall infiltration of 4 mm/day intensity and which lasts for different time durations (8, 15 and 30 days). The simulations were carried out using the commercial software module SIGMA/W and considering different initial soil suction conditions P1, P2, P3 and P4. The soil surface heave and the radial induced forces on the pipeline ring (i.e., Axial , Shear forces and bending moments ) results indicated that following the changes of suction the rainfall infiltration can cause considerable additional loads on the buried pipeline. Moreover, these loads are proportionally related to the initial soil suction conditions as well as to the rainfall infiltration time duration. The study highlighted that the unsaturated behavior of expansive soils because of their volume instability are very sensitive to climatic conditions and can exert adverse effects on pipelines buried within such soils. As a result, consistent pipeline design should seriously consider the study of the effect of the climatic conditions on the overall stability of the pipeline structure.

Highlights

Buried pipelines are important lifeline infrastructures used by many countries and companies to transport fluids to remediate the strong hydraulic and energy resources inequalities over the world
The numerical analyses were conducted to simulate the effect of the volume changes that occur in the expansive soil subjected to a saturation process acting as an external hydraulic loading on the buried pipeline
For the four initial suction profile conditions P1, P2, P3 and P4, the suction variations were evaluated as transient seepage analysis under 4 mm/day rainfall infiltration using SIGMA/W software where the hydraulic response is governed by the soil water characteristic curve SWCC and the permeability function K

Summary

Introduction

Buried pipelines are important lifeline infrastructures used by many countries and companies to transport fluids (i.e., water or gas) to remediate the strong hydraulic and energy resources inequalities over the world. Landslides, fault movements as well as shrink/swell soil displacements can exert important additional loadings on structures especially for pipelines buried within expansive soils. These loadings may damage these structures or disturb their normal operations whenever their magnitudes reach the strength limits of the structure material. Professional and academic forensic surveys have revealed that the unsaturated behavior of expansive soils is the main cause of the reported damages that occurred on many types of structures such as lightweight structures and buildings [1, 2], water transport canals used in agriculture activities [3]. Severe damages were reported on buried pipelines [4, 5] in many parts of the world such as arid and semi-arid regions, as a result of deformations induced by volume changes that characterize expansive soils [6, 7]

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Results

Conclusion