The Hai Phong-Ha Long coastal area,with its World Natural Heritage site of Ha Long Bay-Cat Ba islands,has been under intense pressure from rapid development to meet the socio-economic goals set by Hai Phong City and Q...The Hai Phong-Ha Long coastal area,with its World Natural Heritage site of Ha Long Bay-Cat Ba islands,has been under intense pressure from rapid development to meet the socio-economic goals set by Hai Phong City and Quang Ninh Province.As such,urgent land needs for infrastructure construction of economic sectors and urbanization have led to intensive coastal reclamation and seafill leveling,and their environmental consequences.The objective of this study is to assess the adverse environmental effects of coastal reclamation in the Hai Phong—Ha Long area,focusing on ecosystems,environmental quality,and seabed morphology at a regional scale.To achieve this objective,the study employed the regular techniques of environmental assessment methods,such as checklists,matrices,network diagrams,and overlay maps,to appraise these environmental consequences.The results show three main impacted natural components,including coastal ecosystems,environmental qualities,and morphological seabeds,besides coastline changes and socio-economic issues.The most impacted component was coastal ecosystems,followed by the coastal environmental qualities of seawater and sediments,and then the morphological seabed.Based on the study results,it is recommended that during the development of an integrated coastal management plan for the coastal area of Hai Phong–Ha Long,environmental issues of coastal reclamation and seafill leveling must be given much attention.展开更多
Benthic habitat mapping is an emerging discipline in the international marine field in recent years,providing an effective tool for marine spatial planning,marine ecological management,and decision-making applications...Benthic habitat mapping is an emerging discipline in the international marine field in recent years,providing an effective tool for marine spatial planning,marine ecological management,and decision-making applications.Seabed sediment classification is one of the main contents of seabed habitat mapping.In response to the impact of remote sensing imaging quality and the limitations of acoustic measurement range,where a single data source does not fully reflect the substrate type,we proposed a high-precision seabed habitat sediment classification method that integrates data from multiple sources.Based on WorldView-2 multi-spectral remote sensing image data and multibeam bathymetry data,constructed a random forests(RF)classifier with optimal feature selection.A seabed sediment classification experiment integrating optical remote sensing and acoustic remote sensing data was carried out in the shallow water area of Wuzhizhou Island,Hainan,South China.Different seabed sediment types,such as sand,seagrass,and coral reefs were effectively identified,with an overall classification accuracy of 92%.Experimental results show that RF matrix optimized by fusing multi-source remote sensing data for feature selection were better than the classification results of simple combinations of data sources,which improved the accuracy of seabed sediment classification.Therefore,the method proposed in this paper can be effectively applied to high-precision seabed sediment classification and habitat mapping around islands and reefs.展开更多
Deep-sea mining has emerged as a critical solution to address global resource shortages;however,the mechanical interaction between tracked mining vehicles(TMVs)and soft seabed sediments presents fundamental engineerin...Deep-sea mining has emerged as a critical solution to address global resource shortages;however,the mechanical interaction between tracked mining vehicles(TMVs)and soft seabed sediments presents fundamental engineering challenges.This study establishes a multiscale modelling framework coupling the discrete element method(DEM)with multi-body dynamics(MBD)to investigate track-seabed dynamic interactions across three operational modes:flat terrain,slope climbing,and ditch surmounting.The simulation framework,validated against laboratory experiments,systematically evaluates the influence of grouser geometry(involute,triangular,and pin-type)and traveling speed(0.2–1.0 m/s)on traction performance,slip rate,and ground pressure distribution.Results reveal rate-dependent traction mechanisms governed by soil microstructural responses:higher speeds enhance peak traction but exacerbate slip instability on complex terrain.Critical operational thresholds are established—0.7 m/s for flat terrain,≤0.5 m/s for slopes and ditches—with distinct grouser optimization strategies:involute grousers achieve 35%–40%slip reduction on slopes through progressive soil engagement,while triangular grousers provide optimal impact resistance during ditch crossing with 30%–35%performance improvement.These findings provide quantitative design criteria and operational guidelines for optimizing TMV structural parameters and control strategies,offering a robust theoretical foundation for enhancing the performance,safety,and reliability of deep-sea mining equipment in complex submarine environments.展开更多
Seabed soils’stress-strain relationships are nonlinear,and the complexity associated with soil constitutive behavior increases substantially as the loading becomes reversed.This study focuses on the constitutive beha...Seabed soils’stress-strain relationships are nonlinear,and the complexity associated with soil constitutive behavior increases substantially as the loading becomes reversed.This study focuses on the constitutive behavior of cohesive seabed soils under monotonic and cyclic wave loadings.The theoretical framework developed is based on Bounding Surface Plasticity,where soil strain-hardening is addressed through a proposed hardening law to calculate plastic strains and their evolution during the loading history.Considering clays and clay-like cohesive soils located mainly on the surface of the seabed,the plastic hardening modulus is updated using deviatoric plastic strains,and a new degradation function,which is a novel contribution in the study,is developed and incorporated into the theoretical framework.The proposed model,whose mathematical formulation is more practical and simpler compared to other similar models for cohesive seabed soils,is integrated into a computer program using an explicit numerical scheme.Then,several drained and undrained monotonic and cyclic triaxial tests for normally and over-consolidated clays are simulated to verify the proposed constitutive formulation.Results indicate that simulations of cyclic triaxial tests using the proposed model successfully capture the essential static and dynamic behavior of cohesive seabed soils,including large number of load cycles.The proposed model stands out with its predictive power and the simplification advantage it brings to the theory through the hardening law compared to previous models,as successfully demonstrated in this study.The proposed model can be used in solving coastal and offshore geotechnical engineering problems with high accuracy.展开更多
Shallow-water seabed reverberation presents a critical disturbance in acoustic propagation,affecting the target detection performance of monostatic sonar.This paper proposes a novel seabed reverberation model integrat...Shallow-water seabed reverberation presents a critical disturbance in acoustic propagation,affecting the target detection performance of monostatic sonar.This paper proposes a novel seabed reverberation model integrating Gaussian beam tracing with seabed scattering physics.The model synthesizes time-domain reverberation signals by superimposing scattering signals received across multiple propagation paths.It accurately resolves scattering signals along distinct paths and enables simulation of reverberation under diverse shallow-water environments by adjusting the marine parameters.Furthermore,we model the seabed reverberation signals in the time domain and the space domain for a cylindrical transceiver array,and provide a detailed statistical characterization of the simulated seabed reverberation signals.Finally,shallow-water seabed reverberation experiments were conducted with a cylindrical transceiver array.Comparisons between shallow-water seabed reverberation measurements and simulation estimates at various sites and transceiver depths demonstrate that the proposed seabed reverberation model can efficiently simulate shallow-water seabed reverberation.展开更多
This study evaluates the physical mechanisms of incident waves as they interact with a porous wavy barrier of finite thickness.A wave-trapping chamber is formed between the thick wavy barrier(TWB)and partially reflect...This study evaluates the physical mechanisms of incident waves as they interact with a porous wavy barrier of finite thickness.A wave-trapping chamber is formed between the thick wavy barrier(TWB)and partially reflecting seawall(PRS).The effect of seabed undulations is incorporated into the wave-trapping analysis of the TWB.The boundary value problem proposed in this study is solved using a multidomain boundary element method within the context of linear potential flow theory.Coefficients such as reflection,runup,horizontal force on PRS,and vertical force on TWB are examined for various structural configurations.The position of seabed undulations is analyzed for four scenarios:i)seabed undulations upwave of the wavy barrier with a trapping chamber,ii)seabed undulations upwave of the wavy barrier without a trapping chamber,iii)seabed undulations underneath the wavy barrier with a trapping chamber,and iv)seabed undulations beneath the wavy barrier without a trapping chamber.The study results are compared with known results to verify their accuracy.The effects of PRS,TWB porosity,trapping chamber,plate thickness,seabed type,and submergence depth on hydrodynamic coefficients are analyzed against relative water depth.The study reveals that the introduction of a porous TWB with a trapping chamber results in minimal hydrodynamic coefficients(reduced reflection and force on a wall)compared to a rigid TWB without a trapping chamber.A comparison of various seabeds is reported for all combinations of TWB with a chamber.The sloping seabed upwave of the barrier with a trapping chamber,20%plate porosity,and 50%wall reflection at an appropriate submergence depth could replace gravity-type breakwaters in deeper waters.This study holds great potential for analyzing wave trapping coefficients by TWB to provide an effective coastal protection system.展开更多
1.Introduction The global transition to green energy has created an unprecedented demand for critical metals and energy resources such as cobalt,nickel,copper,manganese,rare earth elements,and gas hydrates.Against thi...1.Introduction The global transition to green energy has created an unprecedented demand for critical metals and energy resources such as cobalt,nickel,copper,manganese,rare earth elements,and gas hydrates.Against this strategic backdrop,deep-sea mineral and energy resources are increasingly viewed as essential supplements to terrestrial supply bottlenecks and as strategic safeguards for the future low-carbon economy.The international seabed forms a vast strategic resource of global significance,offering great potential to support energy transition and security.Therefore,under sound scientific evaluation and strict regulation,prudent development of this resource should serve both economic needs and the broader goals of sustainable energy transformation[1].展开更多
This article provides a method by which the scour depth and scour width below pipelines,and the scour depth around single vertical piles as well as the time scales of scour for both structures due to bichromatic and b...This article provides a method by which the scour depth and scour width below pipelines,and the scour depth around single vertical piles as well as the time scales of scour for both structures due to bichromatic and bidirectional waves are calculated.The scour and time scale formulae summarized by Sumer and Fredsøe(2002)as well as the bottom shear stress formulae under bichromatic and bidirectional waves by Myrhaug et al.(2023)are used.Results for unidirectional bichromatic waves and symmetrically bidirectional monochromatic waves are provided,showing qualitative agreement with what is expected physically.Qualitative comparisons are made with the data from Schendel et al.’s(2020)small scale laboratory tests on scour around a monopile induced by directionally spread waves.Applications to related cases for pipelines are also suggested.In order to conclude regarding the validity of the method for pipelines and vertical piles,it is required to compare with data in its validity range.展开更多
This study proposed a novel experimental platform to conduct dynamic loading tests of a truncated model steel catenary riser(SCR)within the touchdown zone(TDZ).The facilities of the platform,including a soil tank,a lo...This study proposed a novel experimental platform to conduct dynamic loading tests of a truncated model steel catenary riser(SCR)within the touchdown zone(TDZ).The facilities of the platform,including a soil tank,a loading system,and a soil stirring system,are introduced in detail.A steel pipe with the same diameter as the in situ SCR has been used in the laboratory tests to investigate the vertical motion of the pipe and the effect of the trench on the lateral motion.As the amplitude of the vertical motion increases,the depth of the trench deepens,the bending moment range increases,and the excess pore water pressure at the bottom of the pipeline first accumulates and then dissipates during loading.The development trend of the trench depth and the influence of the soil strength on the SCR bending moment are also studied.During the test,a seabed trench develops,and its shape is similar to that of the in situ trench.展开更多
This paper introduces the recent highly significant activity of China Oilfield Services Ltd. （COSL） in the South China Sea, where COSL conducted pretrial drilling in June of 2008. The paper discusses some key resear...This paper introduces the recent highly significant activity of China Oilfield Services Ltd. （COSL） in the South China Sea, where COSL conducted pretrial drilling in June of 2008. The paper discusses some key research and new practices which led to the fabrication of related equipment which was evaluated in the trial. The market for deepwater drilling in the world has grown over the past 10 years but there are few drilling vessels or platforms suitable for drilling in deepwater or super deepwater. China needs equipment capable of deepwater drilling operations. COSL has some semisubmersible platforms, but they are only considered suitable for operations in water depths less than 475 m. An enabling technology, referred to as an artificial seabed, has been under development by COSL since 2004, and it applies the research results and experiences of many experts in deepwater drilling. COSL hopes this technology will allow drilling to depths of approximately 1 000-1 500m with its current platforms. The paper presents research progress and improvements in fabrication and necessary upgrades to equipment for extending deepwater drilling. The pretrial well was executed at a water depth of nearly 500m. COSL will drill the trial well around 2009 at the same location in the South China Sea.展开更多
The sea bottom in front of a breakwater is scoured under the action of broken waves,and this will affect the stability of the breakwater.In this paper,the scours of sandy seabed in front of a breakwater under the acti...The sea bottom in front of a breakwater is scoured under the action of broken waves,and this will affect the stability of the breakwater.In this paper,the scours of sandy seabed in front of a breakwater under the action of broken waves are investigated experimentally.The depth and range of the scouring trough at the foot of a breakwater are studied,and the influence of open foundation-bed on scouring and depositing is also discussed.In order to apply the research results to practical projects,the scale of model sediment and the scale of scours and depositions are suggested.展开更多
Steel catenary risers （SCR） have become an enabling technology for deepwater environments. A comprehensive review was conducted on recent research that examined interactions between deepwater steel catenary risers a...Steel catenary risers （SCR） have become an enabling technology for deepwater environments. A comprehensive review was conducted on recent research that examined interactions between deepwater steel catenary risers and soft clay seabeds. This included the STRIDE （steel risers in deepwater environments） and CARISIMA （catenary riser soil interaction model for global riser analysis） joint jndustry jrogram＇s test data as well as information from existing papers.展开更多
Haihua Islands is a large artificial island in Danzhou, Hainan. The construction of Haihua Islands changes the hYdrodynamic environment of Yangpu waters, and further affects its morphological change. Delft3D is used t...Haihua Islands is a large artificial island in Danzhou, Hainan. The construction of Haihua Islands changes the hYdrodynamic environment of Yangpu waters, and further affects its morphological change. Delft3D is used to set up a two dimensional nested hydrodynamic and sediment model for Yangpu waters in this paper, and this paper focuses on simulating the velocity and morphological change due to the construction of Haihua Islands after the verification of the model. The seabed deposition is small because of low suspended sediment concentration and less sand source near Yangpu waters. The bed level erodes in the south area of Xiaochan Reef and the Yangpu channel due to the velocity increase in the area.展开更多
Unlike most previous studies on vortex-induced vibrations of a cylinder far from a boundary, this paper focuses on the influences of close proximity of a submarine pipeline to a rigid seabed boundary upon the dynamic ...Unlike most previous studies on vortex-induced vibrations of a cylinder far from a boundary, this paper focuses on the influences of close proximity of a submarine pipeline to a rigid seabed boundary upon the dynamic responses of the pipeline in ocean currents. The effects of gap-to-diameter ratio and those of the stability parameter on the amplitude and frequency responses of a pipeline are investigated experimentally with a novel hydro-elastic facility. A comparison is made between the present experimental results of the amplitude and frequency responses for the pipes with seabed boundary effects and those for wall-free cylinders given by Govardhan and Williamson （2000） and Anand （1985）. The comparison shows that the close proximity of a pipeline to seabed has much influence on the vortex-induced vibrations of the pipeline. Both the width of the lock-in ranges in terms of Vr and the dimensionless amplitude ratio Amax/D become larger with the decrease of the gap-to-diameter ratio e/D, Moreover, the vibration of the pipeline becomes easier to occur and its amplitude response becomes more intensive with the decrease of the stability parameter, while tire pipeline frequency responses are affected slightly by the stability parameter.展开更多
The review covers the development and the state of the art in deep-sea mining rock mechanics,equipment and challenges.It begins by introducing the significance of deep-sea mining,the types and geographical distributio...The review covers the development and the state of the art in deep-sea mining rock mechanics,equipment and challenges.It begins by introducing the significance of deep-sea mining,the types and geographical distribution of deep-sea resources.Section 2 reviews the mechanical properties and fracture mechanism of seabed and related continental rocks,which contributes to the advancement of relevant technologies and theories.Deep-sea mining systems developed by coastal countries are presented in Section 3.Seabed mineral collection systems are critically assessed in Section 4.Subsea mining vehicle is reviewed by walking mechanism and controlling system in Section 5.In Section 6,the development of subsea lifting system is detailed by dividing it into hydraulic and pneumatic lifting modes,and some technical problems in the lifting system are described.An in-depth description of surface support systems is presented in Section 7,which includes the deep-sea mining ship,dynamic positioning system,heave compensation system,launch and retrieval system,mineral disposing system as well as the storage and transferring systems.Section 8 discusses the challenges in the deep-sea mining,in terms of natural occurrence conditions,international legal framework and cooperative mining,environmental protection and economic benefits,etc.Finally,a brief summary and some aspects of prospective research are presented in Section 9.展开更多
The hydroelastic analysis and sonoelastic analysis methods are incorporated with the Green＇s function of the Pekeris ocean hydro-acoustic waveguide model to produce a three-dimensional sonoelastic analysis method for...The hydroelastic analysis and sonoelastic analysis methods are incorporated with the Green＇s function of the Pekeris ocean hydro-acoustic waveguide model to produce a three-dimensional sonoelastic analysis method for ships in the ocean hydro-acoustic environment. The seabed condition is represented by a penetrable boundary of prescribed density and sound speed. This method is employed in this paper to predict the vibration and acoustic radiation of a 1 500 t Small Water Area Twin Hull （SWATH） ship in shallow sea acoustic environment. The wet resonant frequencies and radiation sound source levels are predicted and compared with the measured results of the ship in trial.展开更多
基金supported by the project“Development of Comprehensive Solutions for Environmental Management in the Northeast Coastal Waters of Viet Nam in an Age of Global Changes”(Code:NDT/ITA/2024/07)under the framework of the bilateral scientific and technological cooperation program between Vietnam and Italy(2024-2027).
文摘The Hai Phong-Ha Long coastal area,with its World Natural Heritage site of Ha Long Bay-Cat Ba islands,has been under intense pressure from rapid development to meet the socio-economic goals set by Hai Phong City and Quang Ninh Province.As such,urgent land needs for infrastructure construction of economic sectors and urbanization have led to intensive coastal reclamation and seafill leveling,and their environmental consequences.The objective of this study is to assess the adverse environmental effects of coastal reclamation in the Hai Phong—Ha Long area,focusing on ecosystems,environmental quality,and seabed morphology at a regional scale.To achieve this objective,the study employed the regular techniques of environmental assessment methods,such as checklists,matrices,network diagrams,and overlay maps,to appraise these environmental consequences.The results show three main impacted natural components,including coastal ecosystems,environmental qualities,and morphological seabeds,besides coastline changes and socio-economic issues.The most impacted component was coastal ecosystems,followed by the coastal environmental qualities of seawater and sediments,and then the morphological seabed.Based on the study results,it is recommended that during the development of an integrated coastal management plan for the coastal area of Hai Phong–Ha Long,environmental issues of coastal reclamation and seafill leveling must be given much attention.
基金Supported by the National Natural Science Foundation of China(Nos.42376185,41876111)the Shandong Provincial Natural Science Foundation(No.ZR2023MD073)。
文摘Benthic habitat mapping is an emerging discipline in the international marine field in recent years,providing an effective tool for marine spatial planning,marine ecological management,and decision-making applications.Seabed sediment classification is one of the main contents of seabed habitat mapping.In response to the impact of remote sensing imaging quality and the limitations of acoustic measurement range,where a single data source does not fully reflect the substrate type,we proposed a high-precision seabed habitat sediment classification method that integrates data from multiple sources.Based on WorldView-2 multi-spectral remote sensing image data and multibeam bathymetry data,constructed a random forests(RF)classifier with optimal feature selection.A seabed sediment classification experiment integrating optical remote sensing and acoustic remote sensing data was carried out in the shallow water area of Wuzhizhou Island,Hainan,South China.Different seabed sediment types,such as sand,seagrass,and coral reefs were effectively identified,with an overall classification accuracy of 92%.Experimental results show that RF matrix optimized by fusing multi-source remote sensing data for feature selection were better than the classification results of simple combinations of data sources,which improved the accuracy of seabed sediment classification.Therefore,the method proposed in this paper can be effectively applied to high-precision seabed sediment classification and habitat mapping around islands and reefs.
基金financially supported by the National Key Research and Development Program of China-Young Scientist Project(No.2024YFC2815400)the National Natural Science Foundation of China(No.52588202).
文摘Deep-sea mining has emerged as a critical solution to address global resource shortages;however,the mechanical interaction between tracked mining vehicles(TMVs)and soft seabed sediments presents fundamental engineering challenges.This study establishes a multiscale modelling framework coupling the discrete element method(DEM)with multi-body dynamics(MBD)to investigate track-seabed dynamic interactions across three operational modes:flat terrain,slope climbing,and ditch surmounting.The simulation framework,validated against laboratory experiments,systematically evaluates the influence of grouser geometry(involute,triangular,and pin-type)and traveling speed(0.2–1.0 m/s)on traction performance,slip rate,and ground pressure distribution.Results reveal rate-dependent traction mechanisms governed by soil microstructural responses:higher speeds enhance peak traction but exacerbate slip instability on complex terrain.Critical operational thresholds are established—0.7 m/s for flat terrain,≤0.5 m/s for slopes and ditches—with distinct grouser optimization strategies:involute grousers achieve 35%–40%slip reduction on slopes through progressive soil engagement,while triangular grousers provide optimal impact resistance during ditch crossing with 30%–35%performance improvement.These findings provide quantitative design criteria and operational guidelines for optimizing TMV structural parameters and control strategies,offering a robust theoretical foundation for enhancing the performance,safety,and reliability of deep-sea mining equipment in complex submarine environments.
基金funded by the Istanbul Technical University Research Projects Unit(BAP)with project number 37606.
文摘Seabed soils’stress-strain relationships are nonlinear,and the complexity associated with soil constitutive behavior increases substantially as the loading becomes reversed.This study focuses on the constitutive behavior of cohesive seabed soils under monotonic and cyclic wave loadings.The theoretical framework developed is based on Bounding Surface Plasticity,where soil strain-hardening is addressed through a proposed hardening law to calculate plastic strains and their evolution during the loading history.Considering clays and clay-like cohesive soils located mainly on the surface of the seabed,the plastic hardening modulus is updated using deviatoric plastic strains,and a new degradation function,which is a novel contribution in the study,is developed and incorporated into the theoretical framework.The proposed model,whose mathematical formulation is more practical and simpler compared to other similar models for cohesive seabed soils,is integrated into a computer program using an explicit numerical scheme.Then,several drained and undrained monotonic and cyclic triaxial tests for normally and over-consolidated clays are simulated to verify the proposed constitutive formulation.Results indicate that simulations of cyclic triaxial tests using the proposed model successfully capture the essential static and dynamic behavior of cohesive seabed soils,including large number of load cycles.The proposed model stands out with its predictive power and the simplification advantage it brings to the theory through the hardening law compared to previous models,as successfully demonstrated in this study.The proposed model can be used in solving coastal and offshore geotechnical engineering problems with high accuracy.
基金The Youth Project of National Natural Science Foundation of China under contract No.12304507the Natural Science Foundation of Guangdong Province,China under contract No.2024A1515011512+2 种基金the Stable Supporting Fund of Acoustic Science and Technology Laboratory under contract No.JCKYS2025SSJS010the Fundamental Research Funds for the Central Universities under contract No.20720240108the Special Project for Marine Economy Development of Guangdong Province,China under contract No.GDNRC2023-47.
文摘Shallow-water seabed reverberation presents a critical disturbance in acoustic propagation,affecting the target detection performance of monostatic sonar.This paper proposes a novel seabed reverberation model integrating Gaussian beam tracing with seabed scattering physics.The model synthesizes time-domain reverberation signals by superimposing scattering signals received across multiple propagation paths.It accurately resolves scattering signals along distinct paths and enables simulation of reverberation under diverse shallow-water environments by adjusting the marine parameters.Furthermore,we model the seabed reverberation signals in the time domain and the space domain for a cylindrical transceiver array,and provide a detailed statistical characterization of the simulated seabed reverberation signals.Finally,shallow-water seabed reverberation experiments were conducted with a cylindrical transceiver array.Comparisons between shallow-water seabed reverberation measurements and simulation estimates at various sites and transceiver depths demonstrate that the proposed seabed reverberation model can efficiently simulate shallow-water seabed reverberation.
文摘This study evaluates the physical mechanisms of incident waves as they interact with a porous wavy barrier of finite thickness.A wave-trapping chamber is formed between the thick wavy barrier(TWB)and partially reflecting seawall(PRS).The effect of seabed undulations is incorporated into the wave-trapping analysis of the TWB.The boundary value problem proposed in this study is solved using a multidomain boundary element method within the context of linear potential flow theory.Coefficients such as reflection,runup,horizontal force on PRS,and vertical force on TWB are examined for various structural configurations.The position of seabed undulations is analyzed for four scenarios:i)seabed undulations upwave of the wavy barrier with a trapping chamber,ii)seabed undulations upwave of the wavy barrier without a trapping chamber,iii)seabed undulations underneath the wavy barrier with a trapping chamber,and iv)seabed undulations beneath the wavy barrier without a trapping chamber.The study results are compared with known results to verify their accuracy.The effects of PRS,TWB porosity,trapping chamber,plate thickness,seabed type,and submergence depth on hydrodynamic coefficients are analyzed against relative water depth.The study reveals that the introduction of a porous TWB with a trapping chamber results in minimal hydrodynamic coefficients(reduced reflection and force on a wall)compared to a rigid TWB without a trapping chamber.A comparison of various seabeds is reported for all combinations of TWB with a chamber.The sloping seabed upwave of the barrier with a trapping chamber,20%plate porosity,and 50%wall reflection at an appropriate submergence depth could replace gravity-type breakwaters in deeper waters.This study holds great potential for analyzing wave trapping coefficients by TWB to provide an effective coastal protection system.
基金financial support from the National Key R&D Program of China(No.2024YFC2815400)the Young Taishan Scholars Program(No.TSQN202507107)+1 种基金the Shandong Natural Science Foundation(No.ZR2025MS647)the European Commission(HORIZON MSCA-2024-PF-01,101200637).
文摘1.Introduction The global transition to green energy has created an unprecedented demand for critical metals and energy resources such as cobalt,nickel,copper,manganese,rare earth elements,and gas hydrates.Against this strategic backdrop,deep-sea mineral and energy resources are increasingly viewed as essential supplements to terrestrial supply bottlenecks and as strategic safeguards for the future low-carbon economy.The international seabed forms a vast strategic resource of global significance,offering great potential to support energy transition and security.Therefore,under sound scientific evaluation and strict regulation,prudent development of this resource should serve both economic needs and the broader goals of sustainable energy transformation[1].
文摘This article provides a method by which the scour depth and scour width below pipelines,and the scour depth around single vertical piles as well as the time scales of scour for both structures due to bichromatic and bidirectional waves are calculated.The scour and time scale formulae summarized by Sumer and Fredsøe(2002)as well as the bottom shear stress formulae under bichromatic and bidirectional waves by Myrhaug et al.(2023)are used.Results for unidirectional bichromatic waves and symmetrically bidirectional monochromatic waves are provided,showing qualitative agreement with what is expected physically.Qualitative comparisons are made with the data from Schendel et al.’s(2020)small scale laboratory tests on scour around a monopile induced by directionally spread waves.Applications to related cases for pipelines are also suggested.In order to conclude regarding the validity of the method for pipelines and vertical piles,it is required to compare with data in its validity range.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51879189 and 52071234).
文摘This study proposed a novel experimental platform to conduct dynamic loading tests of a truncated model steel catenary riser(SCR)within the touchdown zone(TDZ).The facilities of the platform,including a soil tank,a loading system,and a soil stirring system,are introduced in detail.A steel pipe with the same diameter as the in situ SCR has been used in the laboratory tests to investigate the vertical motion of the pipe and the effect of the trench on the lateral motion.As the amplitude of the vertical motion increases,the depth of the trench deepens,the bending moment range increases,and the excess pore water pressure at the bottom of the pipeline first accumulates and then dissipates during loading.The development trend of the trench depth and the influence of the soil strength on the SCR bending moment are also studied.During the test,a seabed trench develops,and its shape is similar to that of the in situ trench.
文摘This paper introduces the recent highly significant activity of China Oilfield Services Ltd. （COSL） in the South China Sea, where COSL conducted pretrial drilling in June of 2008. The paper discusses some key research and new practices which led to the fabrication of related equipment which was evaluated in the trial. The market for deepwater drilling in the world has grown over the past 10 years but there are few drilling vessels or platforms suitable for drilling in deepwater or super deepwater. China needs equipment capable of deepwater drilling operations. COSL has some semisubmersible platforms, but they are only considered suitable for operations in water depths less than 475 m. An enabling technology, referred to as an artificial seabed, has been under development by COSL since 2004, and it applies the research results and experiences of many experts in deepwater drilling. COSL hopes this technology will allow drilling to depths of approximately 1 000-1 500m with its current platforms. The paper presents research progress and improvements in fabrication and necessary upgrades to equipment for extending deepwater drilling. The pretrial well was executed at a water depth of nearly 500m. COSL will drill the trial well around 2009 at the same location in the South China Sea.
基金the National Natural Science Foundation of China!(No.599790 1 9)
文摘The sea bottom in front of a breakwater is scoured under the action of broken waves,and this will affect the stability of the breakwater.In this paper,the scours of sandy seabed in front of a breakwater under the action of broken waves are investigated experimentally.The depth and range of the scouring trough at the foot of a breakwater are studied,and the influence of open foundation-bed on scouring and depositing is also discussed.In order to apply the research results to practical projects,the scale of model sediment and the scale of scours and depositions are suggested.
文摘Steel catenary risers （SCR） have become an enabling technology for deepwater environments. A comprehensive review was conducted on recent research that examined interactions between deepwater steel catenary risers and soft clay seabeds. This included the STRIDE （steel risers in deepwater environments） and CARISIMA （catenary riser soil interaction model for global riser analysis） joint jndustry jrogram＇s test data as well as information from existing papers.
文摘Haihua Islands is a large artificial island in Danzhou, Hainan. The construction of Haihua Islands changes the hYdrodynamic environment of Yangpu waters, and further affects its morphological change. Delft3D is used to set up a two dimensional nested hydrodynamic and sediment model for Yangpu waters in this paper, and this paper focuses on simulating the velocity and morphological change due to the construction of Haihua Islands after the verification of the model. The seabed deposition is small because of low suspended sediment concentration and less sand source near Yangpu waters. The bed level erodes in the south area of Xiaochan Reef and the Yangpu channel due to the velocity increase in the area.
基金The project was financially supported bythe Tenth Five-Year Plan of the Chinese Academy of Sciences (Grant No.KJCX2-SW-L03) .
文摘Unlike most previous studies on vortex-induced vibrations of a cylinder far from a boundary, this paper focuses on the influences of close proximity of a submarine pipeline to a rigid seabed boundary upon the dynamic responses of the pipeline in ocean currents. The effects of gap-to-diameter ratio and those of the stability parameter on the amplitude and frequency responses of a pipeline are investigated experimentally with a novel hydro-elastic facility. A comparison is made between the present experimental results of the amplitude and frequency responses for the pipes with seabed boundary effects and those for wall-free cylinders given by Govardhan and Williamson （2000） and Anand （1985）. The comparison shows that the close proximity of a pipeline to seabed has much influence on the vortex-induced vibrations of the pipeline. Both the width of the lock-in ranges in terms of Vr and the dimensionless amplitude ratio Amax/D become larger with the decrease of the gap-to-diameter ratio e/D, Moreover, the vibration of the pipeline becomes easier to occur and its amplitude response becomes more intensive with the decrease of the stability parameter, while tire pipeline frequency responses are affected slightly by the stability parameter.
基金the support provided by the National Natural Science Foundation of China(Nos.51909075 and 52371275)the China Postdoctoral Science Foundation(No.2021M690879)the Chinese Fundamental Research Funds for the Central Universities(No.B230203007).
文摘The review covers the development and the state of the art in deep-sea mining rock mechanics,equipment and challenges.It begins by introducing the significance of deep-sea mining,the types and geographical distribution of deep-sea resources.Section 2 reviews the mechanical properties and fracture mechanism of seabed and related continental rocks,which contributes to the advancement of relevant technologies and theories.Deep-sea mining systems developed by coastal countries are presented in Section 3.Seabed mineral collection systems are critically assessed in Section 4.Subsea mining vehicle is reviewed by walking mechanism and controlling system in Section 5.In Section 6,the development of subsea lifting system is detailed by dividing it into hydraulic and pneumatic lifting modes,and some technical problems in the lifting system are described.An in-depth description of surface support systems is presented in Section 7,which includes the deep-sea mining ship,dynamic positioning system,heave compensation system,launch and retrieval system,mineral disposing system as well as the storage and transferring systems.Section 8 discusses the challenges in the deep-sea mining,in terms of natural occurrence conditions,international legal framework and cooperative mining,environmental protection and economic benefits,etc.Finally,a brief summary and some aspects of prospective research are presented in Section 9.
文摘The hydroelastic analysis and sonoelastic analysis methods are incorporated with the Green＇s function of the Pekeris ocean hydro-acoustic waveguide model to produce a three-dimensional sonoelastic analysis method for ships in the ocean hydro-acoustic environment. The seabed condition is represented by a penetrable boundary of prescribed density and sound speed. This method is employed in this paper to predict the vibration and acoustic radiation of a 1 500 t Small Water Area Twin Hull （SWATH） ship in shallow sea acoustic environment. The wet resonant frequencies and radiation sound source levels are predicted and compared with the measured results of the ship in trial.
