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Artículos de revistas sobre el tema "Seabed Instability"

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Autor: Grafiati
Publicado: 4 de junio de 2021
Última modificación: 20 de febrero de 2023

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1

Duran, Gerardo, Juan Manuel Mayoral, Edgar Mendoza y Rodolfo Silva. "SEABED INSTABILITY AROUND CAISSON BREAKWATERS". Coastal Engineering Proceedings 1, n.º 33 (11 de octubre de 2012): 13. http://dx.doi.org/10.9753/icce.v33.posters.13.

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A sensibility numerical study, considering the soil conditions found at Frontera Port in Tabasco, Mexico was conducted to identify the variables that govern the response of a seabed-foundation-structure system subject to wave loading. Among all the possible causes of instability, this study deals only with those associated with liquefaction failure of silty-sands due to cyclic shear stresses generated by regular waves. This research was prompted by the accidents that have occurred near Frontera Port, the most serious of which took place in October 2007 when the Usumacinta oil platform settled, causing 21 fatalities. Previous analysis of this accident (Leis, et al, 2007) suggested that the platform did not present any structural failure and that the accident was a result of an unexpected behavior of the seabed; probably liquefaction. In order to offer results regarding coastal protection activities in the study area, the analysis presented here was developed simulating a vertical breakwater similar to that constructed in 2001 at Barcelona instead of the oil platform. Puzrin, et al, 2009 report that in November 2001 four caissons of this breakwater failed due to seabed liquefaction. The adaptation of the design of the vertical breakwater to the study area conditions was estimated by means of the Goda, 1985 formula.
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2

Liu, Hong Jun, Hu Wang, Min Sheng Zhang y Xiu Hai Wang. "Experimental Study on Mechanism of Wave-Induced Silty Seabed Fluidization". Applied Mechanics and Materials 90-93 (septiembre de 2011): 2790–97. http://dx.doi.org/10.4028/www.scientific.net/amm.90-93.2790.

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Abstract. In this study, process of wave-induced silty seabed response was explored in a rectangle flume. Based on the experimental phenomena, the variations of pore water pressure and theory analysis, discussions were made on the mechanism of wave-induced silty seabed instability. Results indicated that seabed under wave nodes would experience fluidization and oscillation under wave actions, obvious pore pressure accumulation was observed at the same time. The mode of wave-induced silty seabed instability was fluidization. The mechanism of wave-induced silty seabed fluidization was a combination of excess pore water pressure and shear failure, the chief factor of fluidization could be ascribed to wave-induced cycling shear stress. The steady state strength was somewhat an expression of the level of wave-induced decrease of soil strenth that could finally reach, therefore, it could be used for the estimation of wave-induced fluidization of silty seabed.
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3

Jeng, Dong-Sheng y Liang Cheng. "Wave-induced seabed instability around a buried pipeline in a poro-elastic seabed". Ocean Engineering 27, n.º 2 (febrero de 2000): 127–46. http://dx.doi.org/10.1016/s0029-8018(98)00046-8.

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4

Chari, T. R., C. R. Dawe y S. A. Barbour. "Model Studies of Wave-Seabed Interactions". Journal of Offshore Mechanics and Arctic Engineering 109, n.º 1 (1 de febrero de 1987): 67–74. http://dx.doi.org/10.1115/1.3256992.

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Several factors such as the wave characteristics, the seabed type, the sediment size, and the porosity characteristics influence the transient porewater pressure response below the mudline due to wave-seabed interaction. Experiments were conducted in a soil-wave tank in which the pressure variation profile inside a porous bed of sand was measured for different wave types. The measured pressures were correlated with simple theories based on wave energy dissipation in permeable seabed. Tests were conducted in which the combination of wave and soil conditions caused soil liquefaction and instability. These results were extrapolated to predict the potential conditions that may cause seabed instability in the Hibernia area of the Newfoundland Grand Banks. The experimental assembly, the results and correlations, and the limitations are discussed in this paper.
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5

Mizutani, Norimi y Ayman M. Mostafa. "Nonlinear Wave-Induced Seabed Instability Around Coastal Structures". Coastal Engineering Journal 40, n.º 2 (junio de 1998): 131–60. http://dx.doi.org/10.1142/s0578563498000091.

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6

Hambly, Edmund C. "Punch‐Through Instability of Jack‐Up on Seabed". Journal of Geotechnical Engineering 111, n.º 4 (abril de 1985): 545–50. http://dx.doi.org/10.1061/(asce)0733-9410(1985)111:4(545).

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7

Zhang, Yongli, Yi Zhao y Zhenxia Yuan. "Effect of Seabed Instability on Pile Soil Pressure". Journal of Physics: Conference Series 1624 (octubre de 2020): 042071. http://dx.doi.org/10.1088/1742-6596/1624/4/042071.

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8

Mostafa, Yasser E. y M. Hesham El Naggar. "Effect of seabed instability on fixed offshore platforms". Soil Dynamics and Earthquake Engineering 26, n.º 12 (diciembre de 2006): 1127–42. http://dx.doi.org/10.1016/j.soildyn.2005.12.010.

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9

Rahman, M. S. "Wave‐induced instability of seabed: Mechanism and conditions". Marine Geotechnology 10, n.º 3-4 (julio de 1991): 277–99. http://dx.doi.org/10.1080/10641199109379896.

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10

HIROBE, Eiichi, Hajime ISHIDA y Chikayoshi YATOMI. "The instability region in anisotropic seabed to water waves". PROCEEDINGS OF HYDRAULIC ENGINEERING 41 (1997): 675–80. http://dx.doi.org/10.2208/prohe.41.675.

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11

Jeng, D. S. "Wave-induced seabed instability in front of a breakwater". Ocean Engineering 24, n.º 10 (noviembre de 1997): 887–917. http://dx.doi.org/10.1016/s0029-8018(96)00046-7.

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12

Wang, J. G., M. R. Karim y P. Z. Lin. "Analysis of seabed instability using element free Galerkin method". Ocean Engineering 34, n.º 2 (febrero de 2007): 247–60. http://dx.doi.org/10.1016/j.oceaneng.2006.01.004.

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13

Gao, Fu-Ping, Xi-Ting Han, Jing Cao, Yong Sha y Jin-Sheng Cui. "Submarine pipeline lateral instability on a sloping sandy seabed". Ocean Engineering 50 (agosto de 2012): 44–52. http://dx.doi.org/10.1016/j.oceaneng.2012.05.012.

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14

Zhai, Hualing, Dong-Sheng Jeng y Zhen Guo. "The Role of 2D Seepage on Sediment Incipient Motion around a Pipeline". Journal of Marine Science and Engineering 9, n.º 6 (27 de mayo de 2021): 580. http://dx.doi.org/10.3390/jmse9060580.

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Pipelines have been used as one of the main transportation methods for the offshore industry, with increasing activities in marine resources recently. Prediction of seabed instability is one of key factors that must be taken into consideration for an offshore pipeline project. As the first step of the scour process, sediment incipient motion has been intensively studied in the past. Most previous investigations didn’t consider the wave-induced seepage in the elevation of sediment motion. In this paper, two-dimensional seepage was considered to modify the conventional Shields number and its associated impact on sediment incipient motion around the trenched pipeline was investigated. Both flat and sloping seabeds are considered. The numerical results indicated that a peak or valley of the modified Shields number was formed below the pipeline and horizontal seepage flow tremendously impact the sediment motion in the vicinity of the pipeline. Parametric analysis concludes: the influence of the seepage around the pipeline becomes more significant in a large wave, shallow water in a seabed with large shear modulus and permeability, and larger pipeline diameter and smaller flow gap ratio. This will make soil particles be more easily dragged away from the seabed.
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15

Liao, Zhou-Quan y Xiao-Li Liu. "Wave-induced residual pore pressure around a buried pipeline". E3S Web of Conferences 261 (2021): 02056. http://dx.doi.org/10.1051/e3sconf/202126102056.

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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.
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16

Gao, Fu-Ping, Ning Wang, Jinhui Li y Xi-Ting Han. "Pipe–soil interaction model for current-induced pipeline instability on a sloping sandy seabed". Canadian Geotechnical Journal 53, n.º 11 (noviembre de 2016): 1822–30. http://dx.doi.org/10.1139/cgj-2016-0071.

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As offshore exploitation moves to deeper waters, ocean currents become the prevailing hydrodynamic loads on pipelines, and at the same time a sloping seabed is always encountered. The prediction of lateral soil resistance is vital in evaluating pipeline on-bottom stability. Unlike previous pipe–soil interaction models used mainly for horizontal seabed conditions, a pipe–soil interaction model for current-induced downslope and upslope instabilities is proposed by using the limit equilibrium approach. The Coulomb’s theory of passive earth pressure for the sloping seabed is incorporated in the derivation. The model verification with existing full-scale tests shows good agreement between the experimental results and predicted ones. Parametric study indicates that the effect of slope angle on pipeline lateral soil resistance is significant in the examined range of slope angle from –15° to 15°. The critical pipeline embedment and corresponding passive pressure decrease approximately linearly with increasing slope angle.
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17

Zen, Kouki, D. S. Jeng, J. R. C. Hsu y Takumi Ohyama. "Wave-Induced Seabed Instability: Difference Between Liquefaction and Shear Failure". Soils and Foundations 38, n.º 2 (junio de 1998): 37–47. http://dx.doi.org/10.3208/sandf.38.2_37.

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18

Nadim, Farrokh, Tore J. Kvalstad y Tom Guttormsen. "Quantification of risks associated with seabed instability at Ormen Lange". Marine and Petroleum Geology 22, n.º 1-2 (enero de 2005): 311–18. http://dx.doi.org/10.1016/j.marpetgeo.2004.10.022.

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19

Liu, Tao, Yueyue Lu, Lei Zhou, Xiuqing Yang y Lei Guo. "Experiment and Analysis of Submarine Landslide Model Caused by Elevated Pore Pressure". Journal of Marine Science and Engineering 7, n.º 5 (15 de mayo de 2019): 146. http://dx.doi.org/10.3390/jmse7050146.

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Hydrate decomposition is an important potential cause of marine geological disasters. It is of great significance to understand the dynamic relationship between hydrate reservoir system and the overlying seabed damage caused by its decomposition. The purpose of this study is to understand the instability and destruction mechanisms of a hydrated seabed using physical simulations and to discuss the effects of different geological conditions on seabed stability. By applying pressurized gas to the low permeability silt layer, the excess pore pressure caused by the decomposition of hydrate is simulated and the physical appearance process of the overlying seabed damage is monitored. According to the test results, two conclusions were drawn in this study: (1) Under the action of excess pore pressure caused by hydrate decomposition, typical phenomena of overlying seabed damage include pockmark deformation and shear–slip failure. In shallower or steeper strata, shear-slip failure occurs in the slope. The existence of initial crack in the stratum is the main trigger cause. In thicker formations or gentler slopes, the surface of the seabed has a collapse deformation feature. The occurrence of cracks in the deep soil layer is the main failure mechanism. (2) It was determined that the thickness and slope of the seabed, among other factors, affect the type and extent of seabed damage.
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20

MEI, CHIANG C. y MATTHEW J. HANCOCK. "Weakly nonlinear surface waves over a random seabed". Journal of Fluid Mechanics 475 (25 de enero de 2003): 247–68. http://dx.doi.org/10.1017/s002211200200280x.

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We study the effects of multiple scattering of slowly modulated water waves by a weakly random bathymetry. The combined effects of weak nonlinearity, dispersion and random irregularities are treated together to yield a nonlinear Schrödinger equation with a complex damping term. Implications for localization and side-band instability are discussed. Transmission and nonlinear evolution of a wave packet past a finite strip of disorder is examined.
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21

Han, Shuang, Dong-Sheng Jeng y Chia-Cheng Tsai. "Response of a Porous Seabed around an Immersed Tunnel under Wave Loading: Meshfree Model". Journal of Marine Science and Engineering 7, n.º 10 (17 de octubre de 2019): 369. http://dx.doi.org/10.3390/jmse7100369.

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Seabed instability surrounding an immersed tunnel is a vital engineering issue regarding the design and maintenance for submarine tunnel projects. In this study, a numerical model based on the local radial basis function collocation method (LRBFCM) is developed to evaluate the seabed behaviour in a marine environment, in which the seabed is treated as the porous medium and governed by Biot’s “ u − p ” approximation. As for the flow field above the seabed, the VARANS equations are used to simulate the fluid motion and properties. The present model is validated with analytical solutions and experimental data which show a good capacity of the integrated model. Both wave and current loading are considered in this study. Parametric studies are carried out to investigate the effects of wave characteristics and soil properties. Based on the numerical results, the maximum liquefaction depth around the immersed tunnel could be deeper under the wave loading with long wave period (T) and large wave height (H). Moreover, a seabed with lower permeability ( K s ) and degree of saturation ( S r ) is more likely to be liquefied.
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22

Chillarige, A. V., N. R. Morgenstern, P. K. Robertson y H. A. Christian. "Seabed instability due to flow liquefaction in the Fraser River delta". Canadian Geotechnical Journal 34, n.º 4 (1 de agosto de 1997): 520–33. http://dx.doi.org/10.1139/t97-019.

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23

Ulker, M. B. C., M. S. Rahman y M. N. Guddati. "Wave-induced dynamic response and instability of seabed around caisson breakwater". Ocean Engineering 37, n.º 17-18 (diciembre de 2010): 1522–45. http://dx.doi.org/10.1016/j.oceaneng.2010.09.004.

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24

Ulker, M. B. C., M. S. Rahman y M. N. Guddati. "Breaking wave-induced response and instability of seabed around caisson breakwater". International Journal for Numerical and Analytical Methods in Geomechanics 36, n.º 3 (18 de agosto de 2011): 362–90. http://dx.doi.org/10.1002/nag.1073.

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25

Wang, Ning, Wengang Qi y Fuping Gao. "Predicting the Instability Trajectory of an Obliquely Loaded Pipeline on a Clayey Seabed". Journal of Marine Science and Engineering 10, n.º 2 (21 de febrero de 2022): 299. http://dx.doi.org/10.3390/jmse10020299.

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Predicting the instability trajectory of an obliquely loaded pipeline on the seabed is vital for the global buckling assessment. To numerically investigate the obliquely loaded pipe–soil interactions, a plane strain elastoplastic finite element model incorporating the adaptive meshing technique and the contact-pair algorithm is employed and verified with the existing experimental data and the analytical predictions. The evolution of slip mechanisms within the underlying soil is simulated, indicating the instability direction of the pipe, and the corresponding ultimate soil resistance is closely correlated. It is also indicated that the ultimate load angle is in the positive correlation with the movement angle, the dimensionless embedment of the pipe and the roughness coefficient of the pipe–soil interface. On the basis of numerous simulations, a force-resultant plasticity model including the bearing capacity envelope and the flow rule is proposed for predicting the behavior of a partially embedded pipeline on the clayey seabed. Finally, an explicit expression with respect to the critical submerged weight of the pipe is derived for distinguishing the lateral instability of a pipe between the ‘light’ and the ‘heavy’ mode.
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26

Liang, Bingchen, Hongli Ge, Libang Zhang y Yong Liu. "Wave resonant scattering mechanism of sinusoidal seabed elucidated by Mathieu Instability theorem". Ocean Engineering 218 (diciembre de 2020): 108238. http://dx.doi.org/10.1016/j.oceaneng.2020.108238.

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27

Rafiei, Amin, M. S. Rahman y M. A. Gabr. "Coupled analysis for response and instability of sloping seabed under wave action". Applied Ocean Research 88 (julio de 2019): 99–110. http://dx.doi.org/10.1016/j.apor.2019.04.017.

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28

Newson, D. W. "Hydrographic Contributions to Safety at Sea 1975–85". Journal of Navigation 39, n.º 1 (enero de 1986): 17–23. http://dx.doi.org/10.1017/s0373463300014193.

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1. ENVIRONMENTAL FACTORS. Since 1975 the inadequacy of knowledge of the depth and shape of the seabed on the continental shelves has become increasingly apparent, as navigational safety has been pushed to further limits in response to economic factors. Less than half of the British continental shelf, defined approximately by the 200 m depth contour, has been surveyed by echo-sounder and only a small proportion to full modern standards. There are inevitably many natural hazards still to be discovered. Inadequate knowledge can have particularly serious effects in heavily trafficked shallow areas, where patches of the seabed may show instability in the form of mobile sandwaves. Seabed wrecks and obstructions, some of them wartime relics, are another problem; thanks to the use of modern sidescan sonar, in 10 years the number of wrecks in the UK area databank has risen from 14000 to 22000.
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29

Zhang, X. H., X. B. Lu, Y. H. Shi, Z. Xia y W. T. Liu. "Centrifuge experimental study on instability of seabed stratum caused by gas hydrate dissociation". Ocean Engineering 105 (septiembre de 2015): 1–9. http://dx.doi.org/10.1016/j.oceaneng.2015.06.006.

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30

Liang, Zuodong y Dong-Sheng Jeng. "A Three-Dimensional Model for the Seabed Response Induced by Waves in Conjunction with Currents in the Vicinity of an Offshore Pipeline Using OpenFOAM". International Journal of Ocean and Coastal Engineering 01, n.º 03 (septiembre de 2018): 1850004. http://dx.doi.org/10.1142/s2529807018500045.

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To better understand the physical processes involved in the wave–seabed–pipeline interactions (WSPI), a three-dimensional numerical model for the wave-induced soil response around an offshore pipeline is proposed in this paper. Seabed instability around an offshore pipeline is one of the key factors that need to be considered by coastal engineers in the design of offshore infrastructures. Most previous investigations into the problem of WSPI have only considered wave conditions and have not included currents, despite the co-existence of waves and currents in natural ocean environments. Unlike previous studies, currents are included in the present study for the numerical modeling of WSPI, using an integrated FVM model, in which the volume-averaged Reynolds-averaged Navier–Stokes (VARANS) equation is used to solve the mean fluid field, while Biot’s consolidation equation is used to describe the solid–pore fluid interaction in the porous medium. Numerical examples demonstrate a significant influence of ocean current direction and angle on the wave-induced pore pressures and the resultant seabed liquefaction around the pipeline, which cannot be observed in two-dimensional (2D) numerical simulation.
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31

Jeng, Dong S. "Wave-induced sea floor dynamics". Applied Mechanics Reviews 56, n.º 4 (1 de julio de 2003): 407–29. http://dx.doi.org/10.1115/1.1577359.

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This article reviews recent developments in the interaction between water waves, seabed, and coastal structures. The scope of the review covers theoretical approaches and physical modeling for the wave-induced soil response, wave damping, and sea floor instability around coastal structures. Important advances in this field of study are summarized and scope for future studies is suggested. There are 208 references cited in this review article.
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32

Wang, Zhu y Liu. "Wave-Induced Seafloor Instability in the Yellow River Delta: Flume Experiments". Journal of Marine Science and Engineering 7, n.º 10 (6 de octubre de 2019): 356. http://dx.doi.org/10.3390/jmse7100356.

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Geological disasters of seabed instability are widely distributed in the Yellow River Delta, posing a serious threat to the safety of offshore oil platforms and submarine pipelines. Waves act as one of the main factors causing the frequent occurrence of instabilities in the region. In order to explore the soil failure mode and the law for pore pressure response of the subaqueous Yellow River Delta under wave actions, in-lab flume tank experiments were conducted in this paper. In the experiments, wave loads were applied with a duration of 1 hour each day for 7 consecutive days; pore water pressure data of the soil under wave action were acquired, and penetration strength data of the sediments were determined after wave action. The results showed that the fine-grained seabed presented an arc-shaped oscillation failure form under wave action. In addition, the sliding surface firstly became deeper and then shallower with the wave action. Interestingly, the distribution of pores substantially coincided with that of sliding surfaces. For the first time, gas holes were identified along with their positioning and angle with respect to the sediments. The presence of gas may serve as a primer for submarine slope failures. The wave process can lead to an increase in the excess pore pressure, while the anti-liquefaction capacity of the sediments was improved, causing a decrease in the excess pore pressure resulting from the next wave process. Without new depositional sediments, the existing surface sediments can form high-strength formation under wave actions. The test results may provide a reference for numerical simulations and engineering practice.
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33

Wang, Xiao, Dong-Sheng Jeng y Chia-Cheng Tsai. "Meshfree Model for Wave-Seabed Interactions Around Offshore Pipelines". Journal of Marine Science and Engineering 7, n.º 4 (28 de marzo de 2019): 87. http://dx.doi.org/10.3390/jmse7040087.

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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.
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34

Yu, Xiaochen, Jingsheng Zhai, Bo Zou, Qi Shao y Guangchao Hou. "A Novel Acoustic Sediment Classification Method Based on the K-Mdoids Algorithm Using Multibeam Echosounder Backscatter Intensity". Journal of Marine Science and Engineering 9, n.º 5 (9 de mayo de 2021): 508. http://dx.doi.org/10.3390/jmse9050508.

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The modern discrimination of sediment is based on acoustic intensity (backscatter) information from high-resolution multibeam echo-sounder systems (MBES). The backscattering intensity, varying with the angle of incidence, reveals the characteristics of seabed sediment. In this study, we propose a novel unsupervised acoustic sediment classification method based on the K-medoids algorithm using multibeam backscattering intensity data. In this method, we use the Lurton parameters model, which is the relationship between the backscattering intensity and incidence, to obtain the backscattering angle corresponding curve, and we use the genetic algorithm to fit the curve by the least-squares method. After extracting the four relevant parameters of the model when the ideal fitting effect was achieved, we input the characteristic parameters obtained from the fitting to the K-medoids clustering model. To validate the proposed classification method, we compare it with the self-organizing map (SOM) neural network classification method under the same parameter settings. The results of the experiment show that when the seabed sediment category is less than or equal to 3, the results of the K-medoids algorithm and the SOM neural network are approximately identical. As the sediment category increases, the SOM neural network shows instability, and it is impossible to see the clear boundaries of the seabed sediment, while the K-medoids category is 5 and the seabed sediment classification is correct. After comparing with field in situ seabed sediment sampling along the MBES survey line, the sediment classification method based on K-medoids is consistent with the distribution of the field sediment sampling. The classification accuracies for bedrock, sandy clay, and silty sand are all above 90%; those for gravel and clay are nearly 80%, and the overall accuracy reaches 89.7%.
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35

Shi, Yumin, Fuping Gao, Ning Wang y Zhenyu Yin. "Coupled Flow-Seepage-Elastoplastic Modeling for Competition Mechanism between Lateral Instability and Tunnel Erosion of a Submarine Pipeline". Journal of Marine Science and Engineering 9, n.º 8 (18 de agosto de 2021): 889. http://dx.doi.org/10.3390/jmse9080889.

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The instability of a partially embedded pipeline under ocean currents involves complex fluid–pipe–soil interactions, which may induce two typical instability modes; i.e., the lateral instability of the pipe and the tunnel erosion of the underlying soil. In previous studies, such two instability modes were widely investigated, but separately. To reveal the competition mechanism between the lateral instability and the tunnel erosion, a coupled flow-seepage-elastoplastic modeling approach was proposed that could realize the synchronous simulation of the pipe hydrodynamics, the seepage flow, and elastoplastic behavior of the seabed soil beneath the pipe. The coupling algorithm was provided for flow-seepage-elastoplastic simulations. The proposed model was verified through experimental and numerical results. Based on the instability criteria for the lateral instability and tunnel erosion, the two instability modes and their corresponding critical flow velocities could be determined. The instability envelope for the flow–pipe–soil interaction was established eventually, and could be described by three parameters; i.e., the critical flow velocity (Ucr), the embedment-to-diameter ratio (e/D), and the non-dimensional submerged weight of the pipe (G). There existed a transition line on the envelope when switching from one instability mode to the other. If the flow velocity of ocean currents gets beyond the instability envelope, either tunnel erosion or lateral instability could be triggered. With increasing e/D or concurrently decreasing G, the lateral instability was more prone to being triggered than the tunnel erosion. The present analyses may provide a physical insight into the dual-mode competition mechanism for the current-induced instability of submarine pipelines.
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36

Day, Kevin, Julie Gale y John Smallwood. "Deepwater Exmouth Plateau, North Carnarvon Basin: preliminary investigations into ridge and furrow features". APPEA Journal 50, n.º 2 (2010): 731. http://dx.doi.org/10.1071/aj09095.

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Numerous fields of long, shallow subsurface linear ridge and furrow features were mapped during the interpretation of a 3D seismic dataset covering Hess Exploration Australia Pty Ltd’s WA–390–P deepwater Exmouth Plateau permit. These kilometre scale features are often slope parallel and have separations of between 100 to 400 metres between ridge crests. Heights range from the limit of seismic resolution up to approximately nine metres. Similar linear shallow subsurface features have been interpreted in the North Falkland Basin in Desire Petroleum’s Tranches C and D permits. Initial investigations suggest that these features appear similar to the Holocene and older mega furrows/palaeo-mega furrows identified along the lower slope/rise in the Gulf of Mexico, most notably along the base of the Sigsbee Escarpment, and along other continental slope/rise settings. Evidence of seabed and shallow sub-seabed sediment instability in the form of slumps and slides together with the effects of shallow sediment deformation and dewatering are also visible across the WA-390-P area. Ridge and furrow features from the deepwater Exmouth Plateau area are described in detail alongside examples from the North Falkland Basin. It is suggested that interaction between gravity driven downslope processes, sediment dewatering and alongslope sedimentary processes could be a possible mechanism of formation for these features. Horizontal and vertical delineation of these features can contribute towards regional understanding of subsurface sediment instability.
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37

Nielsen, Tove y Antoon Kuijpers. "Geohazard studies offshore the Faroe Islands: slope instability, bottom currents and sub-seabed sediment mobilisation". Geological Survey of Denmark and Greenland (GEUS) Bulletin 4 (20 de julio de 2004): 57–60. http://dx.doi.org/10.34194/geusb.v4.4785.

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Prior to the 1990s only few geological investigations of the seabed and the shallow geology around the Faroe Islands had been undertaken (Waagstein & Rasmussen 1975; Nielsen et al. 1981). However, in the 1990s marine geological and in particular seismic investigations were markedly intensified. Since 1993 several studies on the structure of the Faroe Islands margin and seafloor processes have been funded by the European Union, namely the ENAM (European North Atlantic Margin) project I and II (1993–1999) and the STRATAGEM (Stratigraphy of the Glaciated European Margin) project (2000–2003), and these have provided significant new information on the mechanisms shaping the Faroe Islands margin (e.g. Boldreel et al. 1998; Kuijpers et al. 1998a; Nielsen & van Weering 1998; van Weering et al. 1998). Due to the expertise and regional geological knowledge obtained during these projects the Geological Survey of Denmark and Greenland (GEUS) became involved in socalled ‘geohazard’ seabed studies of the Faroe–Shetland Channel in 1997. These investigations were financed by the petroleum industry that had begun to show significant interest in exploration of the Faroe–Shetland Channel area. The studies focused on possible natural risks that would affect submarine structures, such as slope instability and strong bottom currents, and included both shallow seismic data acquisition and sediment core analyses. Most of the work at sea was undertaken with the Russian research vessel Prof. Logachev, and carried out within the framework of the international, UNESCO-supported ‘Training-Through-Research’ (TTR) programme co-ordinated by Moscow State University, Russia. Since 1997, more than three million DKK have been granted for various projects and this work has been documented in 14 classified reports. This paper presents some of the main results from these ‘geohazard’ studies, in particular with respect to the sediment instability affecting the western flank of the Faroe–Shetland Channel, the occurrence of very strong bottom currents in the channel, and the newly discovered mud diapirs at the northern entrance of the channel (Fig. 1).
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38

IMASE, Tatsuya, Kenichi MAEDA, Michio MIYAKE, Kazuhiro TSURUGASAKI, Yutaka SAWADA y Hiroko SUMIDA. "Instability of caisson-type breakwater due to seepage of tsunami into rubble mound and seabed". Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 67, n.º 2 (2011): I_551—I_555. http://dx.doi.org/10.2208/kaigan.67.i_551.

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39

Jeng, D. S. "Mechanism of the wave-induced seabed instability in the vicinity of a breakwater: a review". Ocean Engineering 28, n.º 5 (mayo de 2001): 537–70. http://dx.doi.org/10.1016/s0029-8018(00)00013-5.

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40

Yang, Q. S., H. B. Poorooshasb y S. C. H. Cheung. "Travelling wave-induced liquefaction of sand deposits". Canadian Journal of Civil Engineering 21, n.º 2 (1 de abril de 1994): 186–94. http://dx.doi.org/10.1139/l94-022.

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The sea-floor deposit is assumed to be a saturated porous medium modelled by a two-phase system for which the coupled governing equations are derived from the theory of mixture. A constitutive model based on the generalized plasticity-bounding surface formulation is proposed to describe the soil behavior. An artificial boundary is suggested to deal with the unbounded domain problem. The coupled governing equations and the material model have been implemented into a nonlinear finite element program to analyze the travelling wave-induced liquefaction of seabed deposits. The results of two case studies are presented. The first case examines the response of sand deposit to the wave train at a site of underwater pipelines for nuclear power plants in Lake Ontario where the deposit was found to vary from loose to medium dense. The second case investigates the sea-floor behavior under a storm wave at the Ekofisk oil tank site in the North Sea where the deposit was reported to be dense. The results agree with the field observations. Key words: seabed instability, liquefaction, finite element, plasticity, sand, cyclic loading, travelling wave, unbounded domain.
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41

Geng, Minghui, Haibin Song, Yongxian Guan, Jiang Xin Chen y Yang Bai. "Characteristics and generation mechanism of gullies and mega-pockmarks in the Zhongjiannan Basin, western South China Sea". Interpretation 5, n.º 3 (31 de agosto de 2017): SM49—SM59. http://dx.doi.org/10.1190/int-2016-0216.1.

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The paleoceanography and deep-water circulation process of the South China Sea (SCS) is still poorly understood. We have evaluated multibeam bathymetry and multichannel seismic reflection data acquired by Guangzhou Marine Geological Survey in recent years, and we investigate the characteristics, distribution, and generation mechanism of submarine seabed gullies and mega-pockmarks in the northern Zhongjiannan Basin of the SCS. Our data reveal that there are northwest–southeast-trending gullies and randomly or linearly arraying mega-pockmarks in the northern depression of the Zhongjiannan Basin. Gullies are 1 km or more in width and tens of kilometers in length. The long-axis diameter for the largest mega-pockmarks can reach up to 4293 m. The mega-pockmarks found in the west block of the northern depression are the manifestation of focused fluid flow migrating along shallow inclined faults induced by slumps that reached the seabed. Gullies are trending southeast and perpendicular to the contours of the continental slope, suggesting that gravity flows have played an important role in the evolution of gullies. Our data demonstrate that the gullies have a close relationship with mega-pockmarks, and that they were formed through the interaction of intense focused fluid flow and gravity flows. The pockmarks formed first, subsequently growing in size and number under the effect of subsurface fluid flows. The southeastward moving gravity flow caused discrete pockmarks to coalesce and form immature gullies. After being fully converged, gullies finally become smooth-bottomed and matured. Because gullies and mega-pockmarks are the manifestation of the geologic process of fluid escape at the seabed, they should be taken into account when assessing the potential for gas hydrates and seafloor instability.
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42

Ferrando, Ilaria, Pierluigi Brandolini, Bianca Federici, Antonio Lucarelli, Domenico Sguerso, Danilo Morelli y Nicola Corradi. "Coastal Modification in Relation to Sea Storm Effects: Application of 3D Remote Sensing Survey in Sanremo Marina (Liguria, NW Italy)". Water 13, n.º 8 (9 de abril de 2021): 1040. http://dx.doi.org/10.3390/w13081040.

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Integrated remote sensing techniques, such as photogrammetry from unmanned aerial vehicles (UAV), mobile laser scanners (MLS) and multibeam echosounders (MBES), are particularly effective in detecting and measuring coastal and seabed features and their modifications over time (4D analysis) induced by sea storms. In fact, these techniques allow the production of very high-resolution 3D models, with a continuum between above and below sea level. The present research is focused on the area of Portosole Marina (Sanremo, Western Liguria), affected by a severe sea storm in October 2018 and the following restoration. Two integrated 3D surveys were performed in February 2019 and in November 2019, obtaining accurate and reliable high-definition digital surface models (DSMs) in both emerged and submerged areas. The comparison between the two surveys highlighted volumetric changes in the seabed induced by the sea storm and the effects of a temporary worksite on the emerged and submerged breakwater. In particular, a total deficit of sediments of about 5000 m3 caused an average lowering of about 4 cm over the entire area, concurring with the breakwater instability. This study aims to contribute to the understanding of coastal system resilience within ongoing global climate changes, that is, increasing the intensity of extreme events in the Mediterranean area.
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43

Wiguna, Taufan, Omar Moefti, Rahadian Rahadian y Muhamad Irfan. "SINGLE CHANNEL SEISMIC APPLICATION FOR GAS CHARGED SEDIMENT RECONNAISSANCE IN GEOHAZARD STUDY OF PORT CONSTRUCTION AT WETLAND AREA". Jurnal Neutrino 9, n.º 1 (31 de octubre de 2016): 20. http://dx.doi.org/10.18860/neu.v9i1.3666.

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<p class="abstrak">Gas charged sediment as a one of parameter for geohazard study in infrastructure especially in swamp area. Instability of sediment layer for exampel subsidence and landslide result in geohazard potention that caused by gas charged sediment. Seismic single channel can be used to identufy gas charged sediment location. Seabed morphology is collected from bathymetry and tidal survey. From seismic profile interpretation shows gas charged sediment indication in Line A and Line B. That indication emerged by presence of acoustic turbid zone and acoustic blanking. Line A and Line B location will be spotlight in next geotechnic port construction study.</p><p> </p>
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44

Wang, Hu y Hong-jun Liu. "Evaluation of storm wave-induced silty seabed instability and geo-hazards: A case study in the Yellow River delta". Applied Ocean Research 58 (junio de 2016): 135–45. http://dx.doi.org/10.1016/j.apor.2016.03.013.

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45

Chen, Hao, Yakun Guo, Shiqi Yu, Jisheng Zhang y Sheng Liu. "Experimental Study of the Effect of Backfill Conditions on Soil Responses around a Pipeline under Wave–Current Load". Journal of Marine Science and Engineering 10, n.º 10 (27 de septiembre de 2022): 1384. http://dx.doi.org/10.3390/jmse10101384.

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Waves and currents coexist widely in the ocean, and the interaction of waves and currents plays an important role in the instability of submarine pipelines. So far, most studies have concentrated on discussing the dynamic reaction within the seabed around a pipeline under pure wave action, monotypic sediment, and an exposed or fully buried condition. In this study, the effect of current characteristics (e.g., current velocity and propagation direction) and backfilling conditions (e.g., backfill depth and sand property) on the dynamic response around the submarine pipeline is investigated by conducting laboratory experiments. Pipeline was buried in the excavated trench using three types of sand with the median size of 0.150 mm, 0.300 mm and 0.045 mm, respectively. Five relative backfilled depths, with the ratios of backfill depth over the pipeline diameter being 0, 1/2, 1, 3/2 and 2, were tested. The excess pore pressure was measured simultaneously by using the pore pressure sensors installed around the pipeline surface and beneath the pipeline. Results show that both the pore pressure amplitude and its descent rate gradually decrease with an increasing backfill depth, which decreases the soil liquefaction potential. Under the co-current actions, the decrease rate of the pore pressure along the vertical direction increases with an increasing current velocity. However, the increased current velocity leads to a decrease of the attenuation rate under the counter-current actions compared with the pure wave actions, and the counter-current effect on the pore pressure within the seabed is greater than the co-current. The results indicate that the dynamic response around the pipeline in coarse sand is close to that without the backfill scenario, even if the backfill depth reaches up to two times that of the pipeline diameter. It is found that the larger the median particle size of backfill sand, the smaller the impact on pore pressure within the seabed beneath the pipeline.
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46

Song, Laifu, Hao Ying, Wei Wang, Ning Fan y Xueming Du. "Reliability Modelling of Pipeline Failure under the Impact of Submarine Slides-Copula Method". Mathematics 10, n.º 9 (20 de abril de 2022): 1382. http://dx.doi.org/10.3390/math10091382.

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The instability of seabed slope sediments is the main factor influencing the safety of marine resource development. Therefore, to ensure the safe operation of submarine pipelines under complex and uncertain seabed rock and soil conditions, a reliability model was developed to elucidate the trend of impact-related pipeline damage due to submarine slides. Then, a risk assessment of the damage process of submarine slides impacting pipelines was conducted, which is of great significance for the in-depth safety assessment of pipelines impacted by submarine slides. Based on the copula function, a joint probability distribution model considering the correlation among risk variables was established for rational correlation characterization. A probability analysis method of impact-related pipeline damage attributed to submarine slides based on the copula function was proposed. The Monte Carlo simulation (MCS) method was employed to simulate the random uncertainty in limited observation values and accurately determine the reliability of safe pipeline operation under the action of submarine slides. The conclusions were as follows: (1) Based on the copula function, a joint probability distribution model of risk variables with any marginal distribution function and related structure could be developed. (2) The copula function could reasonably characterize relevant nonnormal distribution characteristics of risk variables and could simulate samples conforming to the distribution pattern of the risk variables. (3) The failure probability calculated with the traditional independent normal distribution model was very low, which could result in a notable overestimation of the reliability of submarine pipelines.
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47

Ingram, W. B. y R. N. Dutt. "Discussion of “ Punch‐Through Instability of Jack‐Up on Seabed ” by Edmund C. Hambly (April, 1985, Vol. 111, No. 4)". Journal of Geotechnical Engineering 113, n.º 4 (abril de 1987): 402–3. http://dx.doi.org/10.1061/(asce)0733-9410(1987)113:4(402).

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48

Hambly, Edmund C. "Closure to “ Punch‐Through Instability of Jack‐Up on Seabed ” by Edmund C. Hambly (April, 1985, Vol. 111, No. 4)". Journal of Geotechnical Engineering 113, n.º 4 (abril de 1987): 403–6. http://dx.doi.org/10.1061/(asce)0733-9410(1987)113:4(403).

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49

Gopinathan, D., M. Venugopal, D. Roy, K. Rajendran, S. Guillas y F. Dias. "Uncertainties in the 2004 Sumatra–Andaman source through nonlinear stochastic inversion of tsunami waves". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, n.º 2205 (septiembre de 2017): 20170353. http://dx.doi.org/10.1098/rspa.2017.0353.

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Numerical inversions for earthquake source parameters from tsunami wave data usually incorporate subjective elements to stabilize the search. In addition, noisy and possibly insufficient data result in instability and non-uniqueness in most deterministic inversions, which are barely acknowledged. Here, we employ the satellite altimetry data for the 2004 Sumatra–Andaman tsunami event to invert the source parameters. We also include kinematic parameters that improve the description of tsunami generation and propagation, especially near the source. Using a finite fault model that represents the extent of rupture and the geometry of the trench, we perform a new type of nonlinear joint inversion of the slips, rupture velocities and rise times with minimal a priori constraints. Despite persistently good waveform fits, large uncertainties in the joint parameter distribution constitute a remarkable feature of the inversion. These uncertainties suggest that objective inversion strategies should incorporate more sophisticated physical models of seabed deformation in order to significantly improve the performance of early warning systems.
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50

del Valle, R. A., E. Yermolin, J. Chiarandini, A. Sanchez Granel y J. C. Lusky. "Methane at the NW of Weddell Sea, Antarctica". Journal of Geological Research 2017 (13 de febrero de 2017): 1–8. http://dx.doi.org/10.1155/2017/5952916.

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The presence of gaseous hydrocarbons (from methane to n-pentane) in the seabed sediments and the bubbling of methane may suggest the presence of gas accumulations in the substrate of the NW Weddell Sea, Antarctica. The release of methane from the frozen ocean substrate adjacent to Seymour Island would be linked to climate instability during Late Cenozoic, when vast areas of the Antarctic continental shelf were flooded during the marine transgression that occurred c. 18,000 years ago, after the Last Glacial Maximum (LGM). As the ice melted, the sea again occupied the regions which it had abandoned. As the transgression was relatively rapid, the sub-air relief was not destroyed but was submerged and the ground had frozen (permafrost) along with it. Thus, the heat flow from the sea to the marine substrate, now flooded, would have destabilized frozen gas accumulations, which were originally formed into terrestrial permafrost during the LGM, similarly to what would have happened in the Arctic.
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