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.

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.

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.

Two-Dimensional Model for Wave-Induced Pore Pressure Accumulation in Marine Sediments

2013 ◽  
Author(s):  
Hongyi Zhao ◽  
Dong-Sheng Jeng ◽  
Huijie Zhang ◽  
Jisheng Zhang
Keyword(s):  
Pore Pressure ◽  
Marine Sediments ◽  
Wave Motion ◽  
Present Model ◽  
Two Dimensional ◽  
New Model ◽  
One Dimensional ◽  
Wave Cycle ◽  
Previous Solution ◽  
Wave Induced

In this paper, a two-dimensional (2D) porous model is established to investigate the predication of the wave-induced pore pressure accumulations in marine sediments. In the new model, the VARANS equation is used as the governing equation for the wave motion, while the Biot’s consolidation theory is used for porous seabed. The present model is verified with the previous experimental data [1] and provides a better prediction of pore pressure accumulation than the previous solution [2]. With the new model, a 2D liquefied zone is formed at the beginning of the process, and then gradually move down. After a certain wave cycle (for example, 30 wave cycles in the numerical example), the liquefaction zone will become one-dimensional (1D) and continuously move down and eventually approaches to a constant. Numerical results also conclude the maximum liquefaction depth increases as wave height increases and in shallow water.

scholarly journals Effects of the Soil Property Distribution Gradient on the Wave-Induced Response of a Non-Homogeneous Seabed

2019 ◽  
Vol 7 (8) ◽  
pp. 281 ◽  
Author(s):  
Titi Sui ◽  
Yu Jin ◽  
Zhaojun Wang ◽  
Chi Zhang ◽  
Jian Shi
Keyword(s):  
Numerical Model ◽  
Dynamic Response ◽  
Soil Properties ◽  
Pore Pressure ◽  
Soil Property ◽  
Induced Response ◽  
Property Distribution ◽  
Effective Stresses ◽  
Soil Distribution ◽  
Wave Induced

The seabed is usually non-homogeneous in the real marine environment, and its response to the dynamic wave loading is of great concern to coastal engineers. Previous studies on the simulation of a non-homogeneous seabed response have mostly adopted a vertically layered seabed, in which homogeneous soil properties are assumed in the governing equations for one specified layer. This neglects the distribution gradient terms of soil property, thus leading to an inaccurate evaluation of the dynamic response of a non-homogeneous seabed. In this study, a numerical model for a wave-induced 3D non-homogeneous seabed response is developed, and the effects of the soil property distribution gradient on the wave-induced response of a non-homogeneous seabed are numerically investigated. The numerical model is validated, and the results of the present simulation agree well with those of previous studies. The validated model is applied to simulate an ideal two-dimensional (2D) vertical non-homogeneous seabed. The model is further applied to model the practical wave-induced dynamic response of a three-dimensional (3D) non-homogeneous seabed around a mono-pile. The difference in pore pressure and soil effective stresses due to the soil distribution gradient is investigated. The effects of the soil distribution gradient on liquefaction are also examined. Results of this numerical study indicate that (1) pore pressure decreases while soil effective stresses increase (the maximum difference of the effective stresses can reach 68.9 % p 0 ) with a non-homogeneous seabed if the distribution gradient terms of soil properties are neglected; (2) the effect of the soil property distribution gradient terms on the pore pressure becomes more significant at the upper seabed, while this effect on the soil effective stresses is enhanced at the lower seabed; (3) the effect of the soil distribution gradient on the seabed response is greatly affected by the wave reflection and diffraction around the pile foundation; and (4) the soil distribution gradient terms can be neglected in the evaluation of seabed liquefaction depth in engineering practice.

scholarly journals 3-D Poro-Elastoplastic Model for Short-Crested Wave-Induced Pore Pressures in a Porous Seabed

2015 ◽  
Vol 9 (1) ◽  
pp. 408-416 ◽  
Author(s):  
Z. S. Wong ◽  
C. C. Liao ◽  
D. S. Jeng
Keyword(s):  
Pore Pressure ◽  
Present Model ◽  
Three Dimensional ◽  
Volumetric Strain ◽  
Soil Characteristics ◽  
Elastoplastic Model ◽  
Experiment Data ◽  
Pore Pressures ◽  
Wave Induced ◽  
Plastic Volumetric Strain

In this paper, a three-dimensional poro-elastoplastic model for the short-crested wave-induced pore pressures in a porous seabed is presented. Unlike the previous models, both elasticity and plasticity of seafloor are considered in the present model. This study considers the effects of wave and soil characteristics on the pore pressures and was validated with the previous wave experiment data. As the numerical analysis shows, higher value of plastic parameter leads to a faster residual pore pressure accumulation, which is closely related to the occurrence of seabed liquefaction. In particular, at the dissipation stage, residual pore pressure sharply decreases when enlarging plastic parameter , which dominates the velocity of accumulation of plastic volumetric strain.

Three-Dimensional Modeling of Wave-Induced Seabed Response Around a Semi-Buried Pipeline: A Small-Scale Case

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Jianfeng Zhu ◽  
Hongyi Zhao
Keyword(s):  
Numerical Model ◽  
Three Dimensional ◽  
The Body ◽  
Navier Stokes ◽  
Small Scale ◽  
Buried Pipeline ◽  
Consolidation Process ◽  
Soil Response ◽  
Wave Flume ◽  
Wave Induced

Abstract In this paper, a three-dimensional integrated numerical model for a small-scale case of wave-induced oscillatory soil response around a semi-buried pipeline (PORO-WSSI-PIPE 3D) is proposed. In this model, we combine the Reynolds-averaged Navier–Stokes (RANS) equations for the 3D wave motions and the Biot’s consolidation equations for a porous elastic seabed foundation through pressure continuity at common boundaries, with pipeline being an elastic and impermeable medium. The computational results are validated through comparison with previous analytical solutions and laboratory wave flume tests, obtaining good agreement. Following validation, the numerical model is applied to simulate wave-seabed-pipeline interaction with different obliquities between pipeline and incident wave, varying from 30 deg to 90 deg. Snapshots of wave-seabed-pipeline interaction, as well as dynamic pore pressure distributions at typical locations in the vicinity of a semi-buried pipeline, are obtained and analyzed. The three-dimensional consolidation process of seabed under gravitational forces including the body forces of a pipeline is also discussed.

scholarly journals Meshfree Model for Wave-Seabed Interactions Around Offshore Pipelines

2019 ◽  
Vol 7 (4) ◽  
pp. 87 ◽  
Author(s):  
Xiao Wang ◽  
Dong-Sheng Jeng ◽  
Chia-Cheng Tsai
Keyword(s):  
Present Model ◽  
Numerical Models ◽  
Degree Of Saturation ◽  
Navier Stokes ◽  
Submarine Pipeline ◽  
Offshore Pipelines ◽  
Soil Response ◽  
Offshore Pipeline ◽  
Proposed Model ◽  
Wave Induced

The evaluation of the wave-induced seabed instability around a submarine pipeline is particularly important for coastal engineers involved in the design of pipelines protection. Unlike previous studies, a meshfree model is developed to investigate the wave-induced soil response in the vicinity of a submarine pipeline. In the present model, Reynolds-Averaged Navier-Stokes (RANS) equations are employed to simulate the wave loading, while Biot’s consolidation equations are adopted to investigate the wave-induced soil response. Momentary liquefaction around an offshore pipeline in a trench is examined. Validation of the present seabed model was conducted by comparing with the analytical solution, experimental data, and numerical models available in the literature, which demonstrates the capacity of the present model. Based on the newly proposed model, a parametric study is carried out to investigate the influence of soil properties and wave characteristics for the soil response around the pipeline. The numerical results conclude that the liquefaction depth at the bottom of the pipeline increases with increasing water period (T) and wave height (H), but decreases as backfilled depth ( H b ), degree of saturation ( S r ) and soil permeability (K) increase.

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.

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