Numerical study for wave-induced pore pressure accumulations around buried pipeline: Effects of back-fill trench layer

2014 ◽  
pp. 1113-1118 ◽  
Author(s):  
H Zhao ◽  
D Jeng
Keyword(s):  
Pore Pressure ◽  
Numerical Study ◽  
Buried Pipeline ◽  
Wave Induced

scholarly journals Two-Dimensional Numerical Study of Seabed Response around a Buried Pipeline under Wave and Current Loading

2019 ◽  
Vol 7 (3) ◽  
pp. 66 ◽  
Author(s):  
Cynthia Foo ◽  
Chencong Liao ◽  
Jinjian Chen
Keyword(s):  
Numerical Model ◽  
Pore Pressure ◽  
Numerical Study ◽  
Current Model ◽  
Navier Stokes ◽  
Buried Pipeline ◽  
Soil Permeability ◽  
Biot’S Equation ◽  
Current Loading ◽  
Wave Induced

The evaluation of the wave-induced seabed response around a buried pipeline has been widely studied. However, the analysis of seabed response around marine structures under the wave and current loadings are still limited. In this paper, an integrated numerical model is proposed to examine the wave and current-induced pore pressure generation, for instance, oscillatory and residual pore pressure, around a buried pipeline. The present wave–current model is based on the Reynolds-Averaged Navier–Stokes (RANS) equation with k - ε turbulence while Biot’s equation is adopted to govern the seabed model. Based on this numerical model, it is found that wave characteristics (i.e., wave period), current velocity and seabed characteristics such as soil permeability, relative density, and shear modulus have a significant effect on the generation of pore pressure around the buried pipeline.

scholarly journals Experimental Study on the Distribution of Wave-Induced Excess Pore Pressure in a Sandy Seabed around a Mat Foundation

2019 ◽  
Vol 7 (9) ◽  
pp. 304
Author(s):  
Yuan ◽  
Liao ◽  
Zhou
Keyword(s):  
Pore Pressure ◽  
Numerical Study ◽  
Experimental Results ◽  
Excess Pore Pressure ◽  
Offshore Platforms ◽  
Pressure Area ◽  
Mat Foundation ◽  
Mat Foundations ◽  
Wave Induced ◽  
Excess Pore

Mat foundations are widely used in jack-up offshore platforms to support and transfer loads. Regarding mat foundations working on the seabed, the excess wave-induced pore pressure is critical to seabed stability, which may finally cause structural failure. Therefore, it is important to investigate the distribution of the excess pore pressure in the seabed around the mat foundation. In this study, experiments were performed to study the excess pore pressure distribution around a mat foundation in scale considering the true load state by recording wave profiles and pore pressures inside a sandy seabed. To guarantee the reliability of experiments, a numerical study was conducted and compared with the experimental results. Experimental results indicate that with the existence of the mat foundation, the excess pore pressure is higher at the region, the range of which is the width of the model mat (Wm) before the structure. The maximum pore pressure appears at 0.55 Wm in front of the center of the mat foundation. In addition, the current significantly increases the range of high pore pressure area and the amplitude of the excess pore pressure. As the mat orientation changes, the position of the maximum pore pressure changes from the front to the edge of the mat.

Numerical Modelling of Wave-Induced Pore Pressure Around a Buried Pipeline: WSPI-3D Model

2010 ◽  
Author(s):  
Behnam Shabani ◽  
Dong-Sheng Jeng ◽  
Jianhong Ye ◽  
Yakun Guo
Keyword(s):  
Pore Pressure ◽  
3D Model ◽  
Present Model ◽  
Three Dimensional ◽  
Comsol Multiphysics ◽  
Fe Model ◽  
Soil Consolidation ◽  
Buried Pipeline ◽  
Wave Induced ◽  
Soil Responses

In this paper, a three-dimensional numerical model is developed to analyze the ocean wave-induced seabed response. The pipeline is assumed to be rigid and anchored within a trench. Quasi-static soil consolidation equations are solved with the aid of the proposed Finite Element (FE) model within COMSOL Multiphysics. The influence of wave obliquity on seabed responses, the pore pressure and soil stresses, are studied. A comprehensive tests of FE meshes is performed to determine appropriate meshes for numerical calculations. The present model is verified with the previous analytical solutions without a pipeline and two-dimensional experimental data with a pipeline. Numerical results suggest that the effect of wave obliquity on soil responses can be explained through the following two mechanisms: (i) geometry-based three-dimensional influences, and (ii) the formation of inversion nodes. However, the influences of wave obliquity on the wave-induced pore pressure are insignificant.

Two-Dimensional Model for Pore Pressure Accumulations in the Vicinity of a Buried Pipeline

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
H.-Y. Zhao ◽  
D.-S. Jeng ◽  
Z. Guo ◽  
J.-S. Zhang
Keyword(s):  
Numerical Model ◽  
Relative Density ◽  
Pore Pressure ◽  
Present Model ◽  
Buried Pipeline ◽  
Offshore Pipeline ◽  
Backfill Materials ◽  
Consolidation Coefficient ◽  
Definition Of ◽  
Wave Induced

In this paper, we presented an integrated numerical model for the wave-induced residual liquefaction around a buried offshore pipeline. In the present model, unlike previous investigations, two new features were added in the present model: (i) new definition of the source term for the residual pore pressure generations was proposed and extended from 1D to 2D; (ii) preconsolidation due to self-weight of the pipeline was considered. The present model was validated by comparing with the previous experimental data for the cases without a pipeline and with a buried pipeline. Based on the numerical model, first, we examined the effects of seabed, wave and pipeline characteristics on the pore pressure accumulations and residual liquefaction. The numerical results indicated a pipe with a deeper buried depth within the seabed with larger consolidation coefficient and relative density can reduce the risk of liquefaction around a pipeline. Second, we investigated the effects of a trench layer on the wave-induced seabed response. It is found that the geometry of the trench layer (thickness and width), as well as the backfill materials (permeability K and relative density Dr) have significant effect on the development of liquefaction zone around the buried pipeline. Furthermore, under certain conditions, partially backfill the trench layer up to one pipeline diameter is sufficient to protect the pipelines from the wave-induced liquefaction.

scholarly journals Poro-Elastoplastic Modelling of Uplift Resistance of Shallowly-Buried Pipelines

2017 ◽  
Author(s):  
Wen-gang Qi ◽  
Yu-min Shi ◽  
Fu-ping Gao
Keyword(s):  
Pore Pressure ◽  
Compressive Force ◽  
Friction Angle ◽  
Soil Resistance ◽  
Buried Pipeline ◽  
Axial Compressive Force ◽  
Uplift Force ◽  
Upheaval Buckling ◽  
Heating And Cooling ◽  
Wave Induced

During operational cycles of heating and cooling of submarine pipelines, variations of temperature and internal pressure may induce excessive axial compressive force along the pipeline and lead to global buckling of the pipeline. Reliable design against upheaval buckling of a buried pipeline requires the uplift response to be reasonably predicted. Under wave loading, the effective stress of soil could be reduced significantly in the seabed under wave troughs. To investigate the effects of wave-induced pore-pressure on the soil resistance to an uplifted buried pipeline, a poro-elastoplastic model is proposed, which is capable of simulating the wave-induced pore-pressure response in a porous seabed and the development of plastic zones while uplifting a shallowly-buried pipeline. The uplift force on the buried pipeline under wave troughs can be generated by the pore-pressure nonuniformly distributed along the pipe periphery. Numerical results show that the value of uplift force generally increases linearly with the wave-induced mudline pressure under troughs. Parametric study indicates that the peak soil resistance (under wave troughs) decreases with increasing wave height and wave period, respectively. The ratio of peak soil resistance under wave action to that without waves is mainly dependent on the normalized wave-induced mudline pressure, but influenced slightly by the internal friction angle of soil.

scholarly journals Wave-induced residual pore pressure around a buried pipeline

2021 ◽  
Vol 261 ◽  
pp. 02056
Author(s):  
Zhou-Quan Liao ◽  
Xiao-Li Liu
Keyword(s):  
Pore Pressure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Wave Loading ◽  
Buried Pipeline ◽  
Marine Structures ◽  
Factors Affecting ◽  
Pressure Development ◽  
Semi Empirical ◽  
Wave Induced

Seabed instability caused by cyclic wave loading is one of the main factors affecting the foundation instability of marine structures, and it is a key problem that needs to be paid attention in the design of marine structures. Based on Biot’s consolidation theory and a semi-empirical formula for calculating residual pore water pressure, the wave-induced residual seabed response around a buried pipeline was investigated by numerical simulation. The correctness of the numerical results is verified by comparing with experimental results. Effect of the self-weight of the buried pipeline on residual pore pressure development and the characteristics of residual pore pressure near the pipeline are discussed.

Cnoidal Wave-Induced Residual Liquefaction in Loosely Deposited Seabed under Coastal Shallow Water

2021 ◽  
Vol 11 (24) ◽  
pp. 11631
Author(s):  
Xiuwei Chai ◽  
Jingyuan Liu ◽  
Yu Zhou
Keyword(s):  
Shallow Water ◽  
Pore Pressure ◽  
Water Environment ◽  
Lateral Spreading ◽  
Stokes Wave ◽  
Cnoidal Wave ◽  
Liquefaction Resistance ◽  
Liquefaction Process ◽  
Wave Induced ◽  
Seabed Soil

This study is aimed at numerically investigating the cnoidal wave-induced dynamics characteristics and the liquefaction process in a loosely deposited seabed floor in a shallow water environment. To achieve this goal, the integrated model FSSI-CAS 2D is taken as the computational platform, and the advanced soil model Pastor–Zienkiewicz Mark III is utilized to describe the complicated mechanical behavior of loose seabed soil. The computational results show that a significant lateral spreading and vertical subsidence could be observed in the loosely deposited seabed floor due to the gradual loss of soil skeleton stiffness caused by the accumulation of pore pressure. The accumulation of pore pressure in the loose seabed is not infinite but limited by the liquefaction resistance line. The seabed soil at some locations could be reached to the full liquefaction state, becoming a type of heavy fluid with great viscosity. Residual liquefaction is a progressive process that is initiated at the upper part of the seabed floor and then enlarges downward. For waves with great height in shallow water, the depth of the liquefaction zone will be greatly overestimated if the Stokes wave theory is used. This study can enhance the understanding of the characteristics of the liquefaction process in a loosely deposited seabed under coastal shallow water and provide a reference for engineering activities.

An experimental and numerical study of the resonant flow between a hull and a wall

2021 ◽  
Vol 930 ◽  
Author(s):  
I.A. Milne ◽  
O. Kimmoun ◽  
J.M.R. Graham ◽  
B. Molin
Keyword(s):  
Vortex Shedding ◽  
Particle Image ◽  
Numerical Study ◽  
Numerical Models ◽  
Vertical Wall ◽  
Liquefied Natural Gas ◽  
Narrow Gap ◽  
Image Velocimetry ◽  
High Degree ◽  
Wave Induced

The wave-induced resonant flow in a narrow gap between a stationary hull and a vertical wall is studied experimentally and numerically. Vortex shedding from the sharp bilge edge of the hull gives rise to a quadratically damped free surface response in the gap, where the damping coefficient is approximately independent of wave steepness and frequency. Particle image velocimetry and direct numerical simulations were used to characterise the shedding dynamics and explore the influence of discretisation in the measurements and computations. Secondary separation was identified as a particular feature which occurred at the hull bilge in these gap flows. This can result in the generation of a system with multiple vortical regions and asymmetries between the inflow and outflow. The shedding dynamics was found to exhibit a high degree of invariance to the amplitude in the gap and the spanwise position of the barge. The new measurements and the evaluation of numerical models of varying fidelity can assist in informing offshore operations such as the side by side offloading from floating liquefied natural gas facilities.

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