Experiments on the Sinking of Marine Pipelines on Clayey Soils

Edgar Mendoza,André Ramos,Miguel Losada,Cristina Afonso,Rodolfo Silva,María G Neves

doi:10.3390/w14050704

Abstract

An experimental study was carried out to investigate seabed-pipeline interactions with regard to soil liquefaction. For a soil with a high proportion (30 to 60%) of fine sediment, four groups of tests were configured to reproduce soil liquefaction around pipelines for different initial pipe depths, pipe densities and wave conditions (wave height and period). The study focused on verifying the theoretically computed areas of soil failure by analyzing the sinking depths of the pipelines. The main findings are that a pipe with a submerged specific weight of less than half that of the soil will move up to the mudline; that the loss of soil loading capacity is more frequently evidenced in a fluid-like behavior of the soil than by an abrupt breaking of the soil matrix; and that the pipes which are totally buried will sink more than half-buried pipes. Moreover, wave action and the specific weight of the pipes seem to play more important roles in the expected behavior of the wave–soil–pipe interaction than the initial water content of the mud.

Highlights

Pipelines are used to transport hydrocarbon products or to transport and dispose of waste waters via a marine outfall
The behavior of submarine pipelines buried in loose granular soils [1], or set on muddy soils is of great interest [2], especially the potential for pipeline floatation [3]
It can be seen that pore-water pressure exceeding the nor abrupt pressure decrease, which means that the soil matrix was not destroyed

Summary

Introduction

Pipelines are used to transport hydrocarbon products or to transport and dispose of waste waters via a marine outfall. Research and development are of great importance in the former because the oil industry is still one of the main drivers of the global economy, and in the latter because the coastal population around the world continues to grow. The good operational working of a marine outfall is extremely important for the environment, the welfare of the nearby population and the local economy. The behavior of submarine pipelines buried in loose granular soils [1] (e.g., silt, fine sand and, in some cases, gravel), or set on muddy soils is of great interest [2], especially the potential for pipeline floatation [3]. Failure of submarine pipelines has been linked to the wave-induced instability of marine deposits, which can lead to liquefaction [2,5,6]

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Conclusion