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Coastal Geohazard and Offshore Geotechnics
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Coastal Geohazard and Offshore Geotechnics

A special issue of Journal of Marine Science and Engineering (ISSN 2077-1312).

Deadline for manuscript submissions: closed (1 April 2019) | Viewed by 69070

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Dong-Sheng Jeng

E-Mail Website
Guest Editor
School of Engineering and Built Environment, Griffith University, Gold Coast Campus, Southport, QLD 4222, Australia
Interests: offshore geotechnics; ocean engineering; coastal groundwater hydraulics; offshore wind energy
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Jisheng Zhang

E-Mail Website
Guest Editor
College of Harbor, Coastal and Offshore Engineering, Hohai University, Nanjing 210098, China
Interests: offshore geotechnics; coastal engineering; tidal stream energy
Assoc. Prof. Dr. V.S. Ozgur Kirca

E-Mail Website
Guest Editor
BM SUMER Consultancy & Research, and also, Istanbul Technical University, Department of Civil Engineering, 34467 Maslak, Istanbul, Turkey
Interests: offshore geotechnics; coastal engineering; seabed–structure interaction; marine renewable energy

Special Issue Information

Dear Colleagues,

With the rapid development in the exploration of marine resources, coastal geohazard and offshore geotechnics have attracted a great deal of attention from coastal geotechnical engineers and has achieved significant progress in recent years. The purpose of this Special Issue is to present recent advances in the field of coastal geohazard and offshore geotechnics. Authors are encouraged to submit theoretical, numerical, experimental, and applied articles addressing this theme. Topics include, but are not limited to, the following research topics:

  • fluid–soil–structure interactions around marine infrastructure;
  • seismic-induced seabed liquefaction;
  • scour around marine structures;
  • effects of tsunamis on seabed soil;
  • marine geology;
  • soil characteristics and constitutive model for marine sediments;
  • Sediment re-suspension and transport in coastal estuarine
  • centrifugal modelling for geohazard and offshore geotechnics;
  • geohazard prediction and protection;
  • challenges and novel methods in offshore foundation design.;
  • submarine landslide;
  • impact of climate change on geohazard.

Prof. Dr. Dong-Sheng Jeng
Prof. Dr. Jisheng Zhang
Assoc. Prof. Dr. V.S. Ozgur Kirca
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Journal of Marine Science and Engineering is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • seabed instability
  • fluid-soil-structure interactions
  • coastal dynamics
  • coastal disaster
  • soil constitutive model
  • liquefaction
  • scour
  • submarine landslide
  • marine geology

Published Papers (19 papers)

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Editorial

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5 pages, 155 KiB  
Editorial
Coastal Geohazard and Offshore Geotechnics
by Dong-Sheng Jeng, Jisheng Zhang and Özgür Kirca
J. Mar. Sci. Eng. 2020, 8(12), 1011; https://doi.org/10.3390/jmse8121011 - 10 Dec 2020
Cited by 1 | Viewed by 1884
Abstract
With the rapid development in the exploration of marine resources, coastal geohazard and offshore geotechnics have attracted a great deal of attention from coastal geotechnical engineers and has achieved significant progress in recent years [...] Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)

Research

Jump to: Editorial

16 pages, 4870 KiB  
Article
Seismic Dynamics of Pipeline Buried in Dense Seabed Foundation
by Yan Zhang, Jianhong Ye, Kunpeng He and Songgui Chen
J. Mar. Sci. Eng. 2019, 7(6), 190; https://doi.org/10.3390/jmse7060190 - 20 Jun 2019
Cited by 7 | Viewed by 4040
Abstract
Submarine pipeline is a type of important infrastructure in petroleum industry used for transporting crude oil or natural gas. However, submarine pipelines constructed in high seismic intensity zones are vulnerable of attacks from seismic waves. It is important and meaningful in engineering design [...] Read more.
Submarine pipeline is a type of important infrastructure in petroleum industry used for transporting crude oil or natural gas. However, submarine pipelines constructed in high seismic intensity zones are vulnerable of attacks from seismic waves. It is important and meaningful in engineering design to comprehensively understand the seismic wave-induced dynamics characteristics of submarine pipelines. In this study, taking the coupled numerical model FSSI-CAS 2D as the tool, the seismic dynamics of a submarine steel pipeline buried in dense soil is investigated. Computational results indicate that submarine pipeline buried in dense seabed soil strongly responds to seismic wave. The peak acceleration could be double of that of input seismic wave. There is no residual pore pressure in the dense seabed. Significant resonance of the pipeline is observed in horizontal direction. Comparative study shows that the lateral boundary condition which can avoid wave reflection on it, such as laminar boundary and absorbing boundary should be used for seabed foundation domain in computation. Finally, it is proven that the coupled numerical model FSSI-CAS 2D is applicable to evaluate the seismic dynamics of submarine pipeline. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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23 pages, 4431 KiB  
Article
Scour Effects on the Lateral Behavior of a Large-Diameter Monopile in Soft Clay: Role of Stress History
by Ben He, Yongqing Lai, Lizhong Wang, Yi Hong and Ronghua Zhu
J. Mar. Sci. Eng. 2019, 7(6), 170; https://doi.org/10.3390/jmse7060170 - 01 Jun 2019
Cited by 31 | Viewed by 4907
Abstract
Scouring of soil around large-diameter monopile will alter the stress history, and therefore the stiffness and strength of the soil at shallow depth, with important consequence to the lateral behavior of piles. The existing study is mainly focused on small-diameter piles under scouring, [...] Read more.
Scouring of soil around large-diameter monopile will alter the stress history, and therefore the stiffness and strength of the soil at shallow depth, with important consequence to the lateral behavior of piles. The existing study is mainly focused on small-diameter piles under scouring, where the soil around a pile is analyzed with two simplified approaches: (I) simply removing the scour layers without changing the strength and stiffness of the remaining soils, or (II) solely considering the effects of stress history on the soil strength. This study aims to investigate and quantify the scour effect on the lateral behavior of monopile, based on an advanced hypoplastic model considering the influence of stress history on both soil stiffness and strength. It is revealed that ignorance about the stress history effect (due to scouring) underestimates the extent of the soil failure wedge around the monopile, while overestimates soil stiffness and strength. As a result, a large-diameter pile (diameter D = 5 m) in soft clay subjected to a souring depth of 0.5 D has experienced reductions in ultimate soil resistance and initial stiffness of the p-y curves by 40% and 26%, and thus an increase of pile head deflection by 49%. Due to the inadequacy to consider the stress history effects revealed above, the existing approach (I) has led to non-conservative estimation, while the approach (II) has resulted in an over-conservative prediction. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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20 pages, 4744 KiB  
Article
An Approach to Assess the Stability of Unsaturated Multilayered Coastal-Embankment Slope during Rainfall Infiltration
by Jian-feng Zhu, Chang-fu Chen and Hong-yi Zhao
J. Mar. Sci. Eng. 2019, 7(6), 165; https://doi.org/10.3390/jmse7060165 - 29 May 2019
Cited by 6 | Viewed by 3383
Abstract
This study aims to develop a simple but effective approach to investigate the stability of an unsaturated and multilayered coastal-embankment slope during the rainfall, in which a Random Search Algorithm (RSA) based on the random sampling idea of the Monte Carlo method was [...] Read more.
This study aims to develop a simple but effective approach to investigate the stability of an unsaturated and multilayered coastal-embankment slope during the rainfall, in which a Random Search Algorithm (RSA) based on the random sampling idea of the Monte Carlo method was employed to obtain the most dangerous circular sliding surface, whereas the safety factor of the unsaturated slope was calculated by the modified Morgenstern–Price method. Firstly, two typical distributions of matric suction were illustrated and the associated methods for determining the strength parameters of unsaturated soil were developed. Based on this, the Morgenstern–Price method was further modified to calculate the safety factor, and RSA was adopted to locate the most dangerous sliding surface of the unsaturated multilayered coastal-embankment slope. Finally, the slope breaking process under rainfall infiltration was simulated through continuously searching the critical slip surfaces under different groundwater levels by RSA. The results indicated that the stability of the unsaturated embankment slope was gradually deteriorated with the increase of rainfall infiltration. It was also found that both of the distributions of the matrix suction (ua-uw) and the suction angle (φb) had significant effects on the safety factor of the embankment slope. Basically, linear distribution of (ua-uw) along the depth and linear relationship between φb and (ua-uw) should be adopted in assessing the stability of the unsaturated multilayered coastal-embankment slope. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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10 pages, 2654 KiB  
Article
Giant Submarine Landslide in the South China Sea: Evidence, Causes, and Implications
by Chaoqi Zhu, Sheng Cheng, Qingping Li, Hongxian Shan, Jing’an Lu, Zhicong Shen, Xiaolei Liu and Yonggang Jia
J. Mar. Sci. Eng. 2019, 7(5), 152; https://doi.org/10.3390/jmse7050152 - 17 May 2019
Cited by 29 | Viewed by 7082
Abstract
Submarine landslides can be tremendous in scale. They are one of the most important processes for global sediment fluxes and tsunami generation. However, studies of prodigious submarine landslides remain insufficient. In this review paper, we compile, summarize, and reanalyze the results of previous [...] Read more.
Submarine landslides can be tremendous in scale. They are one of the most important processes for global sediment fluxes and tsunami generation. However, studies of prodigious submarine landslides remain insufficient. In this review paper, we compile, summarize, and reanalyze the results of previous studies. Based on this reanalysis, we discover the giant Baiyun–Liwan submarine slide in the Pearl River Mouth Basin, South China Sea. We describe three concurrent pieces of evidence from ~23 Ma to 24 Ma, the Oligocene–Miocene boundary, for this landslide: the shoreward shift of the shelf break in the Baiyun Sag, the slump deposition to the southeast, and the abrupt decrease in the accumulation rate on the lower continental slope. This landslide extends for over 250 km, and the total affected area of the slide is up to ~35,000–40,000 km2. The scale of the landslide is similar to that of the Storegga slide, which has long been considered to be the largest landslide on earth. We suggest that strike–slip movement along the Red River Fault and ridge jump of the South China Sea caused the coeval Baiyun–Liwan submarine slide. The identification of the giant landslide will promote the understanding of not only its associated geohazards but also the steep rise of the Himalayan orogeny and marine engineering. More attention needs to be paid to areas with repeated submarine landslides and offshore installations. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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11 pages, 5607 KiB  
Article
Field Test on Buoyancy Variation of a Subsea Bottom-Supported Foundation Model
by Tianyi Fang, Guojun Liu, Guanlin Ye, Shang Pan, Haibin Shi and Lulu Zhang
J. Mar. Sci. Eng. 2019, 7(5), 143; https://doi.org/10.3390/jmse7050143 - 13 May 2019
Cited by 6 | Viewed by 2811
Abstract
The bottom-supported foundation is the most important component of offshore platforms, as it provides the major support to the upper structure. The buoyancy of the bottom-supported foundation is a critical issue in platform design because it counteracts parts of the vertical loads. In [...] Read more.
The bottom-supported foundation is the most important component of offshore platforms, as it provides the major support to the upper structure. The buoyancy of the bottom-supported foundation is a critical issue in platform design because it counteracts parts of the vertical loads. In this paper, a model box was designed and installed with earth pressure transducers and pore pressure transducers to simulate the sitting process of the bottom-supported foundation. The buoyancy acting on the model box was calculated on the basis of two different methods, i.e., the water pressure difference between top and bottom surface and the effective stress at the bottom of the model. Field tests with different sitting times were carried out on the saturated soft clay seabed. Numerical coupled analysis was performed to verify the dissipation of the excess pore pressure at the bottom of the model. The results showed that the buoyancy of the model could reach twice the calculated value of Archimedes’ law in the initial stage, however, it eventually stabilized near the theoretical value as the excess pore pressure dissipated. There was a slight fluctuation in buoyancy due to the phase lag of the pore pressure response caused by the low permeability of the seabed. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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17 pages, 3907 KiB  
Article
Dynamic Impedances of Offshore Rock-Socketed Monopiles
by Rui He, Ji Ji, Jisheng Zhang, Wei Peng, Zufeng Sun and Zhen Guo
J. Mar. Sci. Eng. 2019, 7(5), 134; https://doi.org/10.3390/jmse7050134 - 09 May 2019
Cited by 18 | Viewed by 3420
Abstract
With the development of offshore wind energy in China, more and more offshore wind turbines are being constructed in rock-based sea areas. However, the large diameter and thin-walled steel rock-socketed monopiles are very scarce at present, and both the construction and design are [...] Read more.
With the development of offshore wind energy in China, more and more offshore wind turbines are being constructed in rock-based sea areas. However, the large diameter and thin-walled steel rock-socketed monopiles are very scarce at present, and both the construction and design are very difficult. For the design, the dynamic safety during the whole lifetime of the wind turbine is difficult to guarantee. Dynamic safety of a turbine is mostly controlled by the dynamic impedances of the rock-socketed monopile, which are still not well understood. How to choose the appropriate impedances of the socketed monopiles so that the wind turbines will neither resonant nor be too conservative is the main problem. Based on a numerical model in this study, the accurate impedances are obtained for different frequencies of excitation, different soil and rock parameters, and different rock-socketed lengths. The dynamic stiffness of monopile increases, while the radiative damping decreases as rock-socketed depth increases. When the weathering degree of rock increases, the dynamic stiffness of the monopile decreases, while the radiative damping increases. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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19 pages, 5553 KiB  
Article
Dynamic Response of Offshore Open-Ended Pile under Lateral Cyclic Loadings
by Junwei Liu, Zhen Guo, Na Zhu, Hui Zhao, Ankit Garg, Longfei Xu, Tao Liu and Changchun Fu
J. Mar. Sci. Eng. 2019, 7(5), 128; https://doi.org/10.3390/jmse7050128 - 03 May 2019
Cited by 12 | Viewed by 3203
Abstract
Foundations for offshore wind turbines (OWTs) are mainly open-ended piles that are subjected to cyclic loadings caused by winds, waves and currents. This study aims to investigate the dynamic responses of open-ended pipe pile under lateral cyclic loadings, as well as the characteristics [...] Read more.
Foundations for offshore wind turbines (OWTs) are mainly open-ended piles that are subjected to cyclic loadings caused by winds, waves and currents. This study aims to investigate the dynamic responses of open-ended pipe pile under lateral cyclic loadings, as well as the characteristics of the soil plug and surrounding soil. Both large-scale indoor model test and discrete element simulation were adopted in this study. The test results show that the resistance of each part of the pipe pile increases linearly with depth during the process of pile driving. The pile side resistance degradation effect was also observed along with the friction fatigue. The soil plug formation rate decreases gradually with an increase in the pile depth. The influence range in the surrounding soil is about 5~6 times of the pile diameter. The cumulative displacement of the pile head increases with the number of cycles. Lateral tangential stiffness and lateral ultimate bearing capacity decreases with an increase in number of cycles. The severe disturbance range of soil around the pile is 2~3 times of the pile diameter. The center of rotation of the pile body is about 0.8 times of the pile body depth. The side frictional resistance and lateral pressure of the pile body is found to fluctuate along the pile body. Additionally, the lateral pressure and side friction resistance decreases gradually with decreasing tendency of the former more than the latter. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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29 pages, 3335 KiB  
Article
Effects of Principal Stress Rotation on the Fluid-Induced Soil Response in a Porous Seabed
by Zhengxu Li, Dong-Sheng Jeng, Jian-Feng Zhu and Hongyi Zhao
J. Mar. Sci. Eng. 2019, 7(5), 123; https://doi.org/10.3390/jmse7050123 - 28 Apr 2019
Cited by 4 | Viewed by 2810
Abstract
Principal stress rotation (PSR) is an important feature for describing the stress status of marine sediments subject to cyclic loading. In this study, a one-way coupled numerical model that combines the fluid model (for wave–current interactions) and the soil model (including the effect [...] Read more.
Principal stress rotation (PSR) is an important feature for describing the stress status of marine sediments subject to cyclic loading. In this study, a one-way coupled numerical model that combines the fluid model (for wave–current interactions) and the soil model (including the effect of PSR) was established. Then, the proposed model was incorporated into the finite element analysis procedure DIANA-SWANDYNE II with PSR effects incorporated and further validated by the experimental data available in the literature. Finally, the impact of PSR on the pore-water pressures and the resultant seabed liquefaction were investigated using the numerical model, and it was found that PSR had a significant influence on the seabed response to combined wave and current loading. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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24 pages, 4951 KiB  
Article
Bridge Scour Identification and Field Application Based on Ambient Vibration Measurements of Superstructures
by Wen Xiong, C.S. Cai, Bo Kong, Xuefeng Zhang and Pingbo Tang
J. Mar. Sci. Eng. 2019, 7(5), 121; https://doi.org/10.3390/jmse7050121 - 26 Apr 2019
Cited by 29 | Viewed by 4221
Abstract
A scour identification method was developed based on the ambient vibration measurements of superstructures. The Hangzhou Bay Bridge, a cable-stayed bridge with high scour potential, was selected to illustrate the application of this method. Firstly, two ambient vibration measurements were conducted in 2013 [...] Read more.
A scour identification method was developed based on the ambient vibration measurements of superstructures. The Hangzhou Bay Bridge, a cable-stayed bridge with high scour potential, was selected to illustrate the application of this method. Firstly, two ambient vibration measurements were conducted in 2013 and 2016 by installing the acceleration sensors on the girders and pylon. By modal analysis, the natural frequencies of the superstructures were calculated with respect to different mode shapes. Then, by tracing the change of dynamic features between two measurements in 2013 and 2016, the discrepancies of the support boundary conditions, i.e., at the foundation of the Hangzhou Bay Bridge, were detected, which, in turn, qualitatively identified the existence of bridge foundation scour. Secondly, an FE model of the bridge considering soil-pile interaction was established to further quantify the scour depth in two steps. (1) The stiffness of the soil springs representing the support boundary of the bridge was initially identified by the model updating method. In this step, the principle for a successful identification is to make the simulation results best fit the measured natural frequencies of those modes insensitive to the scour. (2) Then, using the updated FE model, the scour depth was identified by updating the depth of supporting soils. In this step, the principle of model updating is to make the simulation results best fit the measured natural frequency changes of those modes sensitive to the scour. Finally, a comparison to the underwater terrain map of the Hangzhou Bay Bridge was carried out to verify the accuracy of the predicted scour depth. Based on the study in this paper, it shows that the proposed method for identifying bridge scour based on the ambient vibration measurements of superstructures is effective and convenient. It is feasible to quickly assess scour conditions for a large number of bridges without underwater devices and operations. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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17 pages, 6647 KiB  
Article
Stability Analysis of Near-Wellbore Reservoirs Considering the Damage of Hydrate-Bearing Sediments
by Xiaoling Zhang, Fei Xia, Chengshun Xu and Yan Han
J. Mar. Sci. Eng. 2019, 7(4), 102; https://doi.org/10.3390/jmse7040102 - 13 Apr 2019
Cited by 13 | Viewed by 2945
Abstract
The stability of hydrate-bearing near-wellbore reservoirs is one of the key issues in gas hydrate exploitation. In most previous investigations, the damage evolution process of the sediment structure and its effect on near-wellbore reservoir stability have been neglected. Therefore, the damage variable is [...] Read more.
The stability of hydrate-bearing near-wellbore reservoirs is one of the key issues in gas hydrate exploitation. In most previous investigations, the damage evolution process of the sediment structure and its effect on near-wellbore reservoir stability have been neglected. Therefore, the damage variable is introduced into a multi-field coupled model based on continuous damage theory and multi-field coupling theory. A thermo-hydro-mechanical-chemical (THMC) multi-field coupling mathematical model considering damage of hydrate-bearing sediments is established. The effects of damage of hydrate-bearing sediments on the thermal field, seepage field, and mechanical field are considered. Finally, the distributions of hydrate saturation, pore pressure, damage variable, and effective stress of a near-wellbore reservoir in gas hydrate exploitation by depressurization are calculated, and the stability of a hydrate-bearing near-wellbore reservoir is analyzed using the model. Through calculation and analysis, it is found that structural damage of hydrate-bearing sediments has an adverse effect on the stability of hydrate-bearing near-wellbore reservoirs. The closer to the wellbore, the worse the reservoir stability, and the near-wellbore reservoir stability is the worst in the direction of minimum horizontal ground stress. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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18 pages, 1805 KiB  
Article
Meshfree Model for Wave-Seabed Interactions Around Offshore Pipelines
by Xiao Xiao Wang, Dong-Sheng Jeng and Chia-Cheng Tsai
J. Mar. Sci. Eng. 2019, 7(4), 87; https://doi.org/10.3390/jmse7040087 - 28 Mar 2019
Cited by 18 | Viewed by 2856
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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15 pages, 2773 KiB  
Article
Two-Dimensional Numerical Study of Seabed Response around a Buried Pipeline under Wave and Current Loading
by Cynthia Su Xin Foo, Chencong Liao and Jinjian Chen
J. Mar. Sci. Eng. 2019, 7(3), 66; https://doi.org/10.3390/jmse7030066 - 13 Mar 2019
Cited by 10 | Viewed by 3645
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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20 pages, 3073 KiB  
Article
Experimental Study and Estimation of Groundwater Fluctuation and Ground Settlement due to Dewatering in a Coastal Shallow Confined Aquifer
by Jiong Li, Ming-Guang Li, Lu-Lu Zhang, Hui Chen, Xiao-He Xia and Jin-Jian Chen
J. Mar. Sci. Eng. 2019, 7(3), 58; https://doi.org/10.3390/jmse7030058 - 01 Mar 2019
Cited by 7 | Viewed by 3152
Abstract
The coastal micro-confined aquifer (MCA) in Shanghai is characterized by shallow burial depth, high artesian head, and discontinuous distribution. It has a significant influence on underground space development, especially where the MCA is directly connected with deep confined aquifers. In this paper, a [...] Read more.
The coastal micro-confined aquifer (MCA) in Shanghai is characterized by shallow burial depth, high artesian head, and discontinuous distribution. It has a significant influence on underground space development, especially where the MCA is directly connected with deep confined aquifers. In this paper, a series of pumping well tests were conducted in the MCA located in such area to investigate the dewatering-induced groundwater fluctuations and stratum deformation. In addition, a numerical method is proposed for the estimation of hydraulic parameter, and an empirical prediction method is developed for dewatering-induced ground settlement. Test results show that groundwater drawdowns and soil settlement can be observed not only in MCA but also in the aquifers underneath it. This indicates that there is a close hydraulic connection among each aquifer. Moreover, the distributions and development of soil settlement at various depths are parallel to those of groundwater drawdowns in most areas of the test site except the vicinity of pumping wells, where collapse-induced subsidence due to high-speed flow may occur. Furthermore, the largest deformation usually occurs at the top of the pumping aquifer instead of the ground surface, because the top layer is expanded due to the stress arch formed in it. Finally, the proposed methods are validated to be feasible according to the pumping well test results and can be employed to investigate the responses of groundwater fluctuations and stratum deformations due to dewatering in MCA. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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18 pages, 6596 KiB  
Article
2D Numerical Study of the Stability of Trench under Wave Action in the Immersing Process of Tunnel Element
by Wei-Yun Chen, Cheng-Lin Liu, Lun-Liang Duan, Hao-Miao Qiu and Zhi-Hua Wang
J. Mar. Sci. Eng. 2019, 7(3), 57; https://doi.org/10.3390/jmse7030057 - 27 Feb 2019
Cited by 6 | Viewed by 2770
Abstract
The evaluation of the trench stability under the action of ocean waves is an important issue in the construction of an immersed tunnel. In this study, a two-dimensional coupling model of a wave-seabed-immersed tunnel is proposed for the dynamic responses of a trench [...] Read more.
The evaluation of the trench stability under the action of ocean waves is an important issue in the construction of an immersed tunnel. In this study, a two-dimensional coupling model of a wave-seabed-immersed tunnel is proposed for the dynamic responses of a trench under wave action in the immersing process of tunnel elements. The porous seabed is characterized by Biot consolidation equations. The k − ε model and RANS equation are adopted to achieve the flow field simulation, and the level set method (LSM) is used to capture the free surface between the water and air. The proposed numerical model is verified using the experimental data and analytical results. Then, the transient liquefaction and shear failure in the vicinity of the trench are discussed at two different conditions, namely, after the foundation groove is excavated and after the tunnel element is placed. The pore pressure amplitude on the weather side slope is demonstrated to be significantly smaller than that on the lee side slope. Also, the distribution of the surrounding flow field and pressure field change dramatically after the tunnel element is settled, leading to the significant changes of seabed stability. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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19 pages, 8051 KiB  
Article
Numerical Simulations of Wave-Induced Soil Erosion in Silty Sand Seabeds
by Zhen Guo, Wenjie Zhou, Congbo Zhu, Feng Yuan and Shengjie Rui
J. Mar. Sci. Eng. 2019, 7(2), 52; https://doi.org/10.3390/jmse7020052 - 20 Feb 2019
Cited by 9 | Viewed by 3316
Abstract
Silty sand is a kind of typical marine sediment that is widely distributed in the offshore areas of East China. It has been found that under continuous actions of wave pressure, a mass of fine particles will gradually rise up to the surface [...] Read more.
Silty sand is a kind of typical marine sediment that is widely distributed in the offshore areas of East China. It has been found that under continuous actions of wave pressure, a mass of fine particles will gradually rise up to the surface of silty sand seabeds, i.e., the phenomenon called wave-induced soil erosion. This is thought to be due to the seepage flow caused by the pore-pressure accumulation within the seabed. In this paper, a kind of three-phase soil model (soil skeleton, pore fluid, and fluidized soil particles) is established to simulate the process of wave-induced soil erosion. In the simulations, the analytical solution for wave-induced pore-pressure accumulation was used, and Darcy flow law, mass conservation, and generation equations were coupled. Then, the time characteristics of wave-induced soil erosion in the seabed were studied, especially for the effects of wave height, wave period, and critical concentration of fluidized particles. It can be concluded that the most significant soil erosion under wave actions appears at the shallow seabed. With the increases of wave height and critical concentration of fluidized particles, the soil erosion rate and erosion degree increase obviously, and there exists a particular wave period that will lead to the most severe and the fastest rate of soil erosion in the seabed. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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18 pages, 3884 KiB  
Article
New Equations to Evaluate Lateral Displacement Caused by Liquefaction Using the Response Surface Method
by Nima Pirhadi, Xiaowei Tang and Qing Yang
J. Mar. Sci. Eng. 2019, 7(2), 35; https://doi.org/10.3390/jmse7020035 - 04 Feb 2019
Cited by 6 | Viewed by 3111
Abstract
Few empirical and semi-empirical approaches have considered the influence of the geology, tectonic source, causative fault type, and frequency content of earthquake motion on lateral displacement caused by liquefaction (DH). This paper aims to address this gap in the literature [...] Read more.
Few empirical and semi-empirical approaches have considered the influence of the geology, tectonic source, causative fault type, and frequency content of earthquake motion on lateral displacement caused by liquefaction (DH). This paper aims to address this gap in the literature by adding an earthquake parameter of the standardized cumulative absolute velocity (CAV5) to the original dataset for analyzing. Furthermore, the complex influence of fine content in the liquefiable layer (F15) is analyzed by deriving two different equations: the first one is for the whole range of parameters, and the second one is for a limited range of F15 values under 28% in order to the F15’s critical value presented in literature. The new response surface method (RSM) approach is applied on the basis of the artificial neural network (ANN) model to develop two new equations. Moreover, to illustrate the capability and efficiency of the developed models, the results of the RSM models are examined by comparing them with an additional three available models using data from the Chi-Chi earthquake sites that were not used for developing the models in this study. In conclusion, the RSM provides a capable tool to evaluate the liquefaction phenomenon, and the results fully justify the complex effect of different values of F15. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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14 pages, 3844 KiB  
Article
Numerical Simulation of a Sandy Seabed Response to Water Surface Waves Propagating on Current
by Dagui Tong, Chencong Liao, Jinjian Chen and Qi Zhang
J. Mar. Sci. Eng. 2018, 6(3), 88; https://doi.org/10.3390/jmse6030088 - 20 Jul 2018
Cited by 7 | Viewed by 3636
Abstract
An integrated numerical model is developed to study wave and current-induced seabed response and liquefaction in a flat seabed. The velocity-inlet wave-generating method is adopted in the present study and the finite difference method is employed to solve the Reynolds-averaged Navier-Stokes equations with [...] Read more.
An integrated numerical model is developed to study wave and current-induced seabed response and liquefaction in a flat seabed. The velocity-inlet wave-generating method is adopted in the present study and the finite difference method is employed to solve the Reynolds-averaged Navier-Stokes equations with k-ε turbulence closure. The model validation demonstrates the capacity of the present model. The parametrical study reveals that the increase of current velocity tends to elongate the wave trough and alleviate the corresponding suction force on the seabed, leading to a decrease in liquefaction depth, while the width of the liquefaction area is enlarged simultaneously. This goes against previous studies, which ignored fluid viscosity, turbulence and bed friction. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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16 pages, 7409 KiB  
Article
Wave (Current)-Induced Pore Pressure in Offshore Deposits: A Coupled Finite Element Model
by Chencong Liao, Dongsheng Jeng, Zaibin Lin, Yakun Guo and Qi Zhang
J. Mar. Sci. Eng. 2018, 6(3), 83; https://doi.org/10.3390/jmse6030083 - 06 Jul 2018
Cited by 7 | Viewed by 3747
Abstract
The interaction between wave and offshore deposits is of great importance for the foundation design of marine installations. However, most previous investigations have been limited to connecting separated wave and seabed sub-models with an individual interface program that transfers loads from the wave [...] Read more.
The interaction between wave and offshore deposits is of great importance for the foundation design of marine installations. However, most previous investigations have been limited to connecting separated wave and seabed sub-models with an individual interface program that transfers loads from the wave model to the seabed model. This research presents a two-dimensional coupled approach to study both wave and seabed processes simultaneously in the same FEM (finite element method) program (COMSOL Multiphysics). In the present model, the progressive wave is generated using a momentum source maker combined with a steady current, while the seabed response is applied with the poro-elastoplastic theory. The information between the flow domain and soil deposits is strongly shared, leading to a comprehensive investigation of wave-seabed interaction. Several cases have been simulated to test the wave generation capability and to validate the soil model. The numerical results present fairly good predictions of wave generation and pore pressure within the seabed, indicating that the present coupled model is a sufficient numerical tool for estimation of wave-induced pore pressure. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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