Research

12 pages, 9967 KiB

Open AccessArticle

Analyses of the Suction Anchor–Sandy Soil Interactions under Slidable Pulling Action Using DEM-FEM Coupling Method: The Interface Friction Effect

by Yu Peng, Bolong Liu, Gang Wang and Quan Wang

J. Mar. Sci. Eng. 2024, 12(4), 535; https://doi.org/10.3390/jmse12040535 - 24 Mar 2024

Viewed by 523

Abstract

The microscale mechanisms underlying the suction anchor–sandy soil interaction under slidable pulling actions of mooring lines remain poorly understood. This technical note addresses this knowledge gap by investigating the suction anchor–sandy soil interaction from micro to macro, with a particular emphasis on the [...] Read more.

The microscale mechanisms underlying the suction anchor–sandy soil interaction under slidable pulling actions of mooring lines remain poorly understood. This technical note addresses this knowledge gap by investigating the suction anchor–sandy soil interaction from micro to macro, with a particular emphasis on the effect of interface friction. The discrete element method (DEM) was utilized to simulate the sandy soil, while the finite element method (FEM) was employed to model the suction anchors. The peak pulling forces in numerical simulations were verified by centrifuge test results. The research findings highlight the significant influence of interface friction on the pulling force–displacement curves, as it affects the patterns of suction anchor–sandy soil interactions. Furthermore, clear relationships were established between the magnitude of interface friction, rotation angle, and pullout displacement of suction anchors. By examining the macro-to-micro behaviors of suction anchor–sandy soil interactions, this study concludes with a comprehensive understanding of failure patterns and their key characteristics under different interface friction conditions. The findings proved that the interface friction not only influences the anti-pullout capacity but also changes the failure patterns of suction anchor–soil interactions in marine engineering. Full article

(This article belongs to the Special Issue Advance in Marine Geotechnical Engineering)

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17 pages, 10007 KiB

Open AccessArticle

Analysis of Factors Affecting Vacuum Formation and Drainage in the Siphon-Vacuum Drainage Method for Marine Reclamation

by Junwei Shu, Jun Wang, Kexing Chen, Qingsong Shen and Hongyue Sun

J. Mar. Sci. Eng. 2024, 12(3), 430; https://doi.org/10.3390/jmse12030430 - 28 Feb 2024

Viewed by 617

Abstract

Traditional drainage methods for marine reclamation typically consume large amounts of energy and have a negative environmental impact. The siphon-vacuum drainage method (SVD) automatically forms a vacuum and drains using less energy. It has significant potential for research and application. In this study, [...] Read more.

Traditional drainage methods for marine reclamation typically consume large amounts of energy and have a negative environmental impact. The siphon-vacuum drainage method (SVD) automatically forms a vacuum and drains using less energy. It has significant potential for research and application. In this study, a theoretical model is used to calculate the vacuum formation process and drainage rate. Qualitative analysis and global sensitivity analysis were conducted to investigate the effect of various factors in the SVD on vacuum formation and drainage. The qualitative analysis suggests that modifying the length and diameter of the siphon pipe and the thickness of the sealing soil column to increase the siphon rate can improve the vacuum degree and drainage efficiency. Sobol global sensitivity analysis reveals that the sealing soil column thickness is the main factor affecting the vacuum, with a first-order sensitivity index accounting for up to 79.48%. The impact of cylinder diameter and the local resistance coefficient (0.43%) can be almost neglected. A fitting equation for estimating the maximum achievable vacuum is provided. Calculations show that the vacuum formed by the SVD can reach over 80 kPa. This work can help optimize SVD design and advance environmentally friendly marine reclamation projects. Full article

(This article belongs to the Special Issue Advance in Marine Geotechnical Engineering)

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15 pages, 4077 KiB

Open AccessArticle

Dynamic Interaction Factor of Pipe Group Piles Considering the Scattering Effect of Passive Piles

by Mingchen Zhong and Kun Meng

J. Mar. Sci. Eng. 2023, 11(9), 1698; https://doi.org/10.3390/jmse11091698 - 28 Aug 2023

Viewed by 838

Abstract

Based on the plane–strain assumption, a calculation model of pile–soil–pile vertical coupling vibration response considering the scattering effect of passive piles is established in this paper. Using this model, the vertical displacement expressions of pile core soil and pile surrounding soil, soil displacement [...] Read more.

Based on the plane–strain assumption, a calculation model of pile–soil–pile vertical coupling vibration response considering the scattering effect of passive piles is established in this paper. Using this model, the vertical displacement expressions of pile core soil and pile surrounding soil, soil displacement attenuation function, and longitudinal complex impedance are obtained. Then, based on the strict pile–soil coupling effect, the displacement of the active pile under vertical load and scattering effect, as well as the displacement of the passive pile under incident waves, are solved separately. A new type of dynamic interaction factor for pipe group piles is derived by introducing scattering effect factors. A numerical example shows that the degenerate solution in this paper is in good agreement with the existing solution, which verifies the rationality of the solution. Considering the scattering effect is helpful in improving the accuracy of vibration response analysis of pile groups. The variation in parameters such as slenderness ratio, pile spacing, and outer diameter has significant effects on the interaction factor, and compared with the solid pile, the influence of parameter change on the pipe pile is smaller. Full article

(This article belongs to the Special Issue Advance in Marine Geotechnical Engineering)

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18 pages, 4069 KiB

Open AccessArticle

Evaluation of Soil–Foundation–Structure Interaction for Large Diameter Monopile Foundation Focusing on Lateral Cyclic Loading

by Jae-Hyun Kim, Yeong-Hoon Jeong, Jeong-Gon Ha and Heon-Joon Park

J. Mar. Sci. Eng. 2023, 11(7), 1303; https://doi.org/10.3390/jmse11071303 - 27 Jun 2023

Cited by 2 | Viewed by 1289

Abstract

In this study, the monotonic and cyclic behavior of an offshore wind turbine with a monopile foundation installed in a sand layer were evaluated in the centrifuge. A simplified offshore wind turbine was modeled, and the lateral load was applied to the tower [...] Read more.

In this study, the monotonic and cyclic behavior of an offshore wind turbine with a monopile foundation installed in a sand layer were evaluated in the centrifuge. A simplified offshore wind turbine was modeled, and the lateral load was applied to the tower under displacement control. The monotonic loading test evaluated ultimate lateral load capacity and bending moment profiles under different loading levels. During cyclic loading, variations of moment-rotation responses, cyclic stiffness, and bending moments along the pile were observed. The initial rotational stiffness of the monopile decreased as the loading level increased. In the fatigue limit state (FLS) and service limit state (SLS) loading conditions, no noticeable variation in stiffness was observed with the number of cycles. However, in the ultimate limit state (ULS), the stiffness of the monopile increased during the first few cycles, followed by a decreasing rate of increase, and reached a certain value. The loading rate had a weakening effect on the monopile–soil interaction, which was supported by the bending moments induced in the monopile. Full article

(This article belongs to the Special Issue Advance in Marine Geotechnical Engineering)

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14 pages, 4241 KiB

Open AccessArticle

Numerical Investigations of Undrained Shear Strength of Sensitive Clay Using Miniature Vane Shear Tests

by Jiayi Shen, Xinyi Wang, Qian Chen, Zhaoyi Ye, Qiaoling Gao and Jiawang Chen

J. Mar. Sci. Eng. 2023, 11(5), 1094; https://doi.org/10.3390/jmse11051094 - 22 May 2023

Viewed by 1915

Abstract

The laboratory miniature vane shear test (MVST) has been widely used to measure the undrained shear strength of marine sediments in offshore engineering. However, the transfer of the soil sample in tube samplers from the seabed to the laboratory releases the in situ [...] Read more.

The laboratory miniature vane shear test (MVST) has been widely used to measure the undrained shear strength of marine sediments in offshore engineering. However, the transfer of the soil sample in tube samplers from the seabed to the laboratory releases the in situ confining stress acting on the soil and will decrease the soil strength. In this research, in order to investigate the effects of confining stress on the undrained shear strength of marine sediments, the Coupled Eulerian-Lagrangian (CEL) approach in ABAQUS is used to model the three-dimensional standard and miniature vane shear tests to estimate the undrained shear strength of sensitive clay with different sensitivities under various stress conditions. Based on the numerical simulation results, a linear strength model that not only considers confining stress effects but also can eliminate the size effects caused by vane blades of MVST is proposed. The proposed model can be used to estimate the undrained shear strength of the sensitive clay under shallow seabed surfaces. Full article

(This article belongs to the Special Issue Advance in Marine Geotechnical Engineering)

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16 pages, 11761 KiB

Open AccessArticle

Influence of Beach Erosion during Wave Action in Designed Artificial Sandy Beach Using XBeach Model: Profiles and Shoreline

by Yingtao Zhou, Xi Feng, Maoyuan Liu and Weiqun Wang

J. Mar. Sci. Eng. 2023, 11(5), 984; https://doi.org/10.3390/jmse11050984 - 06 May 2023

Cited by 1 | Viewed by 1596

Abstract

Beach width is an important factor for tourists’ comfort, and the backshore is a swash zone where sediment moves quickly. Artificial sandy beaches focus on beach width stability and evolution. This paper is based on an artificial beach project in Haikou Bay, where, [...] Read more.

Beach width is an important factor for tourists’ comfort, and the backshore is a swash zone where sediment moves quickly. Artificial sandy beaches focus on beach width stability and evolution. This paper is based on an artificial beach project in Haikou Bay, where, in view of the existing conditions, a new type of beach profile that can protect beach berm and width without being eroded by large wave action. Numerical simulation based on XBeach model were conducted to predict the morphodynamical responses of the beach, including a diagnosis of the erosion spots under storm and normal wave events, respectively. Sediment fluxes along and across the shoreline under varied scenarios, dependent on profile width and backshore slope, were discussed. It was found that normal waves with lower heights and longer periods can induce stronger erosion than storm waves due to the landform of the inner-bay in Haikou Bay. Engineering and biological methods to reduce beach erosion during wave action were discussed. Biological methods such as green-plants-root-system can retain berm surface sediment without allowing it to be transported offshore by wave action. The design concept of this artificial beach project may inspire more beach design and protection projects in coastal zones. Full article

(This article belongs to the Special Issue Advance in Marine Geotechnical Engineering)

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15 pages, 4650 KiB

Open AccessEditor’s ChoiceArticle

Intelligent Model for Dynamic Shear Modulus and Damping Ratio of Undisturbed Marine Clay Based on Back-Propagation Neural Network

by Qi Wu, Zifan Wang, You Qin and Wenbao Yang

J. Mar. Sci. Eng. 2023, 11(2), 249; https://doi.org/10.3390/jmse11020249 - 19 Jan 2023

Cited by 14 | Viewed by 1631

Abstract

In this study, a series of resonant-column experiments were conducted on marine clays from Bohai Bay and Hangzhou Bay, China. The characteristics of the dynamic shear modulus (G) and damping ratio (D) of these marine clays were examined. It [...] Read more.

In this study, a series of resonant-column experiments were conducted on marine clays from Bohai Bay and Hangzhou Bay, China. The characteristics of the dynamic shear modulus (G) and damping ratio (D) of these marine clays were examined. It was found that G and D not only vary with shear strain (γ), but they also have a strong connection with soil depth (H) (reflected by the mean effective confining pressure (σ_m) in the laboratory test conditions). With increasing H (σ_m) and fixed γ, the value of G gradually increases; conversely, the value of D gradually decreases, and this is accompanied by the weakening of the decay or growth rate. An intelligent model based on a back-propagation neural network (BPNN) was developed for the calculation of these parameters. Compared with existing function models, the proposed intelligent model avoids the forward propagation of data errors and the need for human intervention regarding the fitting parameters. The model can accurately predict the G and D characteristics of marine clays at different H (σ_m) and the corresponding γ. The prediction accuracy is universal and does not strictly depend on the number of neurons in the hidden layer of the neural network. Full article

(This article belongs to the Special Issue Advance in Marine Geotechnical Engineering)

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17 pages, 6741 KiB

Open AccessArticle

Experimental Study of the Dynamic Shear Modulus of Saturated Coral Sand under Complex Consolidation Conditions

by Weijia Ma, You Qin, Fei Gao and Qi Wu

J. Mar. Sci. Eng. 2023, 11(1), 214; https://doi.org/10.3390/jmse11010214 - 13 Jan 2023

Cited by 3 | Viewed by 1600

Abstract

The shear modulus is an essential parameter that reflects the mechanical properties of the soil. However, little is known about the shear modulus of coral sand, especially under complex consolidation conditions. In this paper, we present the results of a multi-stage strain-controlled undrained [...] Read more.

The shear modulus is an essential parameter that reflects the mechanical properties of the soil. However, little is known about the shear modulus of coral sand, especially under complex consolidation conditions. In this paper, we present the results of a multi-stage strain-controlled undrained cyclic shear test on saturated coral sand. The influences of several consolidation state parameters: effective mean principal stress (

p_{0}^{'}

), consolidation ratio (k_c), consolidation direction angle (α₀), and coefficient of intermediate principal stress (b) on the maximum shear modulus (G₀), the reference shear strain (γ_r) and the reduction of shear modulus (G) have been investigated. For a specified shear strain level, G will increase with increasing

p_{0}^{'}

and k_c, but decrease with increasing α₀ and b. However, the difference between G for various α₀ and b can be reduced by the increase of shear strain amplitude (γ_a). G₀ shows an increasing trend with the increase of

p_{0}^{'}

and k_c; on the contrary, with the increase of α₀ and b, G₀ shows a decreasing trend. To quantify the effect of consolidation state parameters on G₀, a new index (μ_G0) with four parameters (λ₁, λ₂, λ₃, λ₄) which is related to

p_{0}^{'}

, k_c, α₀, b is proposed to modify the prediction model of G₀ in literature. Similarly, the values of γ_r under different consolidation conditions are also evaluated comprehensively by the four parameters, and the related index (μ_γr) is used to predict γ_r for various consolidation state parameters. A new finding is that there is an identical relationship between normalized shear modulus G/G₀ and normalized shear strain γ_a/γ_r for various consolidation state parameters and the Davidenkov model can describe the G/G₀–γ_a/γ_r curves. By using the prediction model proposed in this paper, an excellent prediction of G can be obtained and the deviation between measured and predicted G is all within ±10%. Full article

(This article belongs to the Special Issue Advance in Marine Geotechnical Engineering)

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