Wave pressures and uplift forces on and scour around submarine pipeline in clayey soil
TL;DR: In this article, the authors investigated wave-induced pressures and uplift forces on a submarine pipeline (exposed, half buried and fully buried) in clayey soil of different consistency index both in regular and random waves.
About: This article is published in Ocean Engineering.The article was published on 2003-02-01. It has received 25 citations till now. The article focuses on the topics: Submarine pipeline & Pore water pressure.
Citations
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TL;DR: The morphology of resultant scour signatures are controlled by the orientation of the wreck structure in relation to the prevailing hydrodynamic regime, the morphology and size of the ship and individual site components, the hydrodynamical regime (currents, waves or combined waves and currents), bathymetry and the geology of the site (seafloor and sub-surface conditions) as mentioned in this paper.
76 citations
TL;DR: A review of the existing research on the interaction between a pipeline and an erodible bed exposed to waves and/or currents is presented in this paper, where the basic mechanism that leads to scour in two-dimensional and three-dimensional (3D) cases is first described, as deduced from small-scale laboratory experiments.
Abstract: A review of the existing research on the interaction between a pipeline and an erodible bed exposed to waves and/or currents is presented. The review covers three topics: scour, liquefaction, and lateral stability of pipelines. The basic mechanism that leads to scour in two-dimensional (2D) and three-dimensional (3D) cases is first described, as deduced from small-scale laboratory experiments. The onset of scour from piping and the developing tunnel erosion are among the processes described. The lateral expansion of the scour hole along the pipe is described, also based primarily on small-scale laboratory experiments. The state of the art of the mathematical/numerical modeling of the scour processes is presented. The associated self-burial of the pipe is described and compared to field observations. In addition to scour, liquefaction may also constitute a risk for pipeline stability. The cause of liquefaction and the resulting consequence for pipeline stability in a natural environment are discuss...
72 citations
TL;DR: In this article, an experimental investigation of seabed evolution behavior around a submarine pipeline and the hydrodynamic forces on the pipeline under regular waves was presented. And the influence of bedform evolution on wave forces was found to vary significantly in different regimes.
28 citations
TL;DR: In this paper, acoustic, seismic, grab sampling and video ground-truthing methods were used for benthic habitat discrimination in the Pisces Reef system, and it was demonstrated that scouring may influence community composition through disturbance mechanisms.
Abstract: The Irish Sea, like many marine areas, is threatened by anthropogenic activities. In particular the Pisces Reef system, a series of smothered rocky reefs are subject to fishing pressures as a result of their position within a Nephrops norvegicus fishery. In an area of sediment deposition and retention the reefs modify the environment by increasing the energy of near-bottom currents which results in localised scouring. This is the first study to attempt to characterise and investigate the ecological functioning of the Pisces Reef system. A multidisciplinary approach was essential for accurate investigation of the area. To facilitate more effective management of the benthic habitats of the Reef system, this study integrates acoustic, seismic, grab sampling and video ground-truthing methods for benthic habitat discrimination. Orientation of the scour hollows also suggest that seabed features could be used to infer dominant flow regimes such as the Irish Sea Gyre. The data revealed significant geology–benthos relationships. A unique biotope was described for the reef habitat and it was demonstrated that scouring may influence community composition through disturbance mechanisms. This study provides preliminary information required for management of a unique habitat within a uniform region.
24 citations
TL;DR: In this article, the authors study the scouring process of a submarine pipeline placed on a weakly cohesive seabed and find that the scour depth depends directly on the hydrodynamic forces acting on the cylinder and the clay content of the soil.
16 citations
References
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TL;DR: In this paper, an analytical model is developed for estimating the pore pressure in the soil and the resulting pressure force on buried pipelines, assuming that the seabed is rigid, homogeneous, and porous with isotropic permeability.
Abstract: Ocean waves induce dynamic pressure responses in permeable seabeds which result in dynamic loads on buried pipelines. An analytical model is developed for estimating the pore pressure in the soil and the resulting pressure force on buried pipelines. It is assumed that the seabed is rigid, homogeneous, and porous with isotropic permeability, that the pore water is incompressible, that fluid flow in the soil is modeled by Darcy's Law, and that the seabed is infinitely deep. A solution is developed for a circular, rigid pipeline using conformal mapping techniques. The solution is compared with the results of both small and large‐scale tests; reasonable agreement is obtained for the small‐scale tests. Wave‐induced seepage forces are evaluated by integrating the pressure distribution over the pipe surface. The magnitude of the force remains constant but the direction rotates around the cylinder once with the passage of each wave. This force may be of sufficient magnitude to be an important consideration in the...
64 citations
TL;DR: In this article, the pore-water pressure field at a pipeline buried in a permeable seabed has been determined from potential theory and the pressure at the pipe integrated to give a net seepage force, of constant magnitude, rotates as the waves pass, thereby tending to force the pipe against the surrounding soil in a cyclic manner.
Abstract: The wave-induced seepage force on buried pipelines has been evaluated theoretically. The seepage force is shown to be large enough to warrant inclusion in future engineering design calculations for pipeline stablity. The pore-water pressure field at a pipeline buried in a permeable seabed has been determined from potential theory and the pressure at the pipe integrated to give a net seepage force. This force, of constant magnitude, rotates as the waves pass, thereby tending to force the pipe against the surrounding soil in a cyclic manner. As each wave trough passes over the pipeline the seepage force acts vertically upwards and when combined with the total bouyant force it increases the likelihood of pipeline flotation.
60 citations
TL;DR: In this paper, the wave-induced cyclic pore-pressure response of a seabed in the vicinity of a submarine pipeline was investigated. And the question of perturbation effects affecting the wave induced pore pressure field by the presence of a stiff and impermeable body of the submarine pipeline is analyzed thoroughly.
41 citations
TL;DR: In this paper, the hydrodynamical force of an undisturbed seabed to water waves is calculated using complex function theory and the technique of conformal mapping, and a good agreement is obtained with existing solutions.
32 citations
TL;DR: In this paper, the authors used boundary integral equation method (BIEM) to estimate the wave-induced pressure on a pipeline in a two-dimensional domain, assuming that the soil structure and fluid are incompressible.
Abstract: Wave‐induced pressures are an important design consideration for oil and natural gas pipelines buried in the marine environment. Realistic problems are three‐dimensional in nature and involve waves approaching the buried pipeline at oblique angles and special pipeline geometries. For fluid flow in a sandy soil where liquefaction does not occur and fluid acceleration terms are negligible, Darcy's law can be used. Assuming that the soil structure and fluid are incompressible, results will show the wave‐induced pressure in the domain being governed by the Laplace equation with associated boundary conditions on the domain boundaries. The pressure distribution on the pipeline is obtained using the boundary integral equation method (BIEM). The BIEM is economical because the computations are performed only on the two‐dimensional surface boundaries of the solution domain rather than throughout the entire three‐dimensional domain. The first problem analyzed is the two‐dimensional case where the pipeline is paralle...
31 citations