Research

22 pages, 8549 KiB

Open AccessArticle

An Application of 3D Cross-Well Elastic Reverse Time Migration Imaging Based on the Multi-Wave and Multi-Component Technique in Coastal Engineering Exploration

by Daicheng Peng, Fei Cheng, Hao Xu and Yuquan Zong

J. Mar. Sci. Eng. 2024, 12(3), 522; https://doi.org/10.3390/jmse12030522 - 21 Mar 2024

Viewed by 613

Abstract

Precise surveys are indispensable in coastal engineering projects. The extensive presence of sand in the coastal area leads to significant attenuation of seismic waves within unsaturated loose sediments. As a result, it becomes challenging for seismic waves to penetrate the weathered zone and [...] Read more.

Precise surveys are indispensable in coastal engineering projects. The extensive presence of sand in the coastal area leads to significant attenuation of seismic waves within unsaturated loose sediments. As a result, it becomes challenging for seismic waves to penetrate the weathered zone and reach the desired depth with significant amount of energy. In this study, the application of three-dimensional (3D) cross-well elastic reverse time migration (RTM) imaging based on multi-wave and multi-component techniques in coastal engineering exploration is explored. Accurate decomposition of vector compressional (P) and shear (S) waves is achieved through two wavefield decoupling algorithms without any amplitude and phase distortion. Additionally, compressional wave pressure components are obtained, which facilitates subsequent independent imaging. This study discusses and analyzes the imaging results of four imaging strategies under cross-correlation imaging conditions in RTM imaging. The analysis leads to the conclusion that scalarizing vector wavefields imaging yields superior imaging of P- and S-waves. Furthermore, the imaging results obtained through this approach are of great physical significance. In order to validate the efficacy of this method in 3D geological structure imaging in coastal areas, RTM imaging experiments were performed on two representative models. The results indicate that the proposed 3D elastic wave imaging method effectively generates accurate 3D cross-well imaging of P- and S-waves. This method utilizes the multi-wave and multi-component elastic wave RTM imaging technique to effectively leverage the Earth’s elastic medium without increasing costs. It provides valuable information about the distribution of subsurface rock layers, interfaces, and other structures in coastal engineering projects. Importantly, this can be achieved without resorting to extensive excavation or drilling operations. This method addresses the limitations of current cross-well imaging techniques, thereby providing abundant and accurate geological and geophysical information for the analysis and interpretation of 3D geological structures in coastal engineering projects. It has important theoretical and practical significance in real-world production, as well as for the study of geological structures in coastal engineering. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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16 pages, 40875 KiB

Open AccessArticle

Pile Driving and the Setup Effect and Underlying Mechanism for Different Pile Types in Calcareous Sand Foundations

by Yan Gao, Zixin Guo and Quan Yuan

J. Mar. Sci. Eng. 2024, 12(1), 133; https://doi.org/10.3390/jmse12010133 - 09 Jan 2024

Viewed by 760

Abstract

The mechanical response and deformation characteristics in calcareous sand foundations during pile driving and setup were studied using model tests combined with the technical methods of tactile pressure sensors and close-range photogrammetry. Different types of piles were considered, including a pipe pile, square [...] Read more.

The mechanical response and deformation characteristics in calcareous sand foundations during pile driving and setup were studied using model tests combined with the technical methods of tactile pressure sensors and close-range photogrammetry. Different types of piles were considered, including a pipe pile, square pile and semi-closed steel pipe pile. The test results show that during pile driving, the pile tip resistance of different piles increases with an increase in the pile insertion depth, and an obvious fluctuation is also obtained due to the particle breakage of the calcareous sand and energy dissipation. Different degrees of particle breakage generated by different type piles make the internal stress variations different, as with the pile tip resistance. The pile tip resistance of model pile A, which simulates a pipe pile, is the highest, followed by model pile B, the simulated square pile. Model pile C, which simulates a semi-closed steel pipe pile, has the smallest pile tip resistance because its particle breakage is the most obvious and the pile tip energy cannot be continuously accumulated. The induced deformation such as sag or uplift on the surface and the associated influence range for the calcareous sand foundation are the smallest for model pile C, followed by model pile B and then model pile A. Model pile A has the most obvious pile driving effect. During the pile setup process after piling, the increase in the total internal stress of model pile B is the largest, and the improvement of the potential bearing capacity is the most obvious, followed by model pile A and model pile C. During the pile setup, the induced uplift deformation in pile driving is recovered and the potential bearing capacity increases due the redistribution and uniformity of the vertical and radial stress distributions in the calcareous sand foundation. Considering the potential bearing capacity of different model piles, the influence range of pile driving, foundation deformation and the pile setup effect, it is suggested to use a pointed square pile corresponding to model pile B in pile engineering in calcareous sand foundations. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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17 pages, 5316 KiB

Open AccessArticle

A Theoretical Methodology and Measurement of Dynamic Characteristics of Wind Turbines with Composite Bucket Foundations

by Jijian Lian, Huan Zhou and Xiaofeng Dong

J. Mar. Sci. Eng. 2024, 12(1), 106; https://doi.org/10.3390/jmse12010106 - 05 Jan 2024

Viewed by 682

Abstract

A composite bucket foundation (CBF) is a new type of supporting structure in offshore wind engineering. Its huge transition part is the key difference compared to other offshore foundations. Firstly, the vibration measurement system of a wind turbine with the CBF is introduced. [...] Read more.

A composite bucket foundation (CBF) is a new type of supporting structure in offshore wind engineering. Its huge transition part is the key difference compared to other offshore foundations. Firstly, the vibration measurement system of a wind turbine with the CBF is introduced. A finite element method (FEM) was developed, and the rigid deformation performance of the transition part was characterized. Then, to clarify the influence of the transition part brings to wind turbines with CBFs, a three-DOF theoretical model was established by simplifying the transition part as a rigid body. Horizontal and rotational foundation stiffness were considered to present the constraint effect below the mudline. Sensitivity studies were conducted on the parameters (including mass, moment of inertia and mass center height) of the transition part. Further, the vibration properties of the CBF structures under different operation load conditions were compared through the theoretical model and the in situ data. The results show that the relative errors between the theoretical model and FEM model are 3.78% to 5.03%, satisfying the accuracy requirements. The parameters of the transition part have varying degrees of influence on the natural frequency, foundation stiffness and vibration response of the wind turbines with CBFs. Compared to wind and 1P loads, the 3P load has a greater influence if the 3P frequency is close to the natural frequency of the wind turbine. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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19 pages, 5360 KiB

Open AccessArticle

An Evaluation of Treatment Effectiveness for Reclaimed Coral Sand Foundation in the South China Sea

by Ting Yao and Wei Li

J. Mar. Sci. Eng. 2023, 11(12), 2288; https://doi.org/10.3390/jmse11122288 - 01 Dec 2023

Cited by 1 | Viewed by 941

Abstract

Mega land reclamation projects have been carried out on the coral reefs in the South China Sea. Coral sand was used as a backfill material through hydraulic filling, with fill heights ranging from 6 to 10 m. To enhance foundation stability, vibro-flotation and [...] Read more.

Mega land reclamation projects have been carried out on the coral reefs in the South China Sea. Coral sand was used as a backfill material through hydraulic filling, with fill heights ranging from 6 to 10 m. To enhance foundation stability, vibro-flotation and impact rolling have been employed. However, the uneven distribution of coral sand, irregular particle shape, lower single-particle strength, and paucity of engineering cases for reference have posed challenges in evaluating the effectiveness of these foundation treatments. In this study, the effectiveness of vibro-flotation and impact rolling on the densification and bearing capacity of coral sand foundations has been investigated. In situ tests, including the plate load test, California Bearing Ratio (CBR) test, density measurements, dynamic penetration test (DPT), and settlement monitoring, were conducted at four distinct zones: an untreated zone, a vibro-flotation zone at a 5 m depth, a vibro-flotation zone at a 10 m depth, and an impact rolling zone. The findings suggest that coral sand exhibits promising characteristics for foundation construction. Seepage and self-weight consolidation following land reclamation formation significantly enhance the compaction degree of the coral sand foundation, thereby meeting the requirements for areas with lower bearing capacity demands. Both vibro-flotation and impact rolling techniques could significantly enhance the foundation-bearing capacity, with marginal differences between them. Since the machinery is simple and construction speed is quick, the impact rolling method is considered to be the most efficient for the treatment of coral sand foundation. The DPT results suggest that the reinforcement effect of both vibro-flotation and impact rolling on the deep foundation is not as substantial as the surface layers. This study provides valuable insights into optimizing foundation treatments for land reclamation projects on the coral reefs. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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17 pages, 5940 KiB

Open AccessArticle

Experimental Study on Mechanical Properties of Marine Mud Slurry Treated by Flocculation-Solidification-High Pressure Filtration Combined Method

by Chao Han, Hongping Xie, Bin Bai, Rongjun Zhang, Yingchao Gao and Zhekun Zhao

J. Mar. Sci. Eng. 2023, 11(12), 2270; https://doi.org/10.3390/jmse11122270 - 29 Nov 2023

Viewed by 762

Abstract

For the massive quantities and negative impacts of dredged mud slurry, its disposal and utilization have become one of the most noticeable issues in the world. In this paper, the flocculation-solidification-high pressure filtration combined method is proposed to effectively dispose of marine mud [...] Read more.

For the massive quantities and negative impacts of dredged mud slurry, its disposal and utilization have become one of the most noticeable issues in the world. In this paper, the flocculation-solidification-high pressure filtration combined method is proposed to effectively dispose of marine mud slurries. The advantages of this method are demonstrated herein in the following three aspects: dewatering performance, material savings, and the shear strength of the treated marine mud slurry. Then, the effects of the anionic polyacrylamide (APAM) dose, composite solidification agent dose, initial water content of marine mud slurries, and initial thickness of geo-bags on the mechanical properties of the marine mud slurry treated by the flocculation-solidification-high pressure filtration combined method are studied. Experimental results show that with increasing doses of APAM, the structures of mud slurries become more stable, and the optimal dose of APAM is determined as 0.16%. Moreover, the increase in the composite solidification agent dose and initial water content of the marine mud slurry, and the decrease in the initial thickness of geo-bags both contribute to the increase in the shear strength of the marine mud slurry treated by the flocculation-solidification-high pressure filtration combined method. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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18 pages, 6986 KiB

Open AccessArticle

Vertical Monotonic and Cyclic Responses of a Bucket in Over-Consolidated Clay

by Jun Jiang, Dong Wang and Dengfeng Fu

J. Mar. Sci. Eng. 2023, 11(11), 2044; https://doi.org/10.3390/jmse11112044 - 25 Oct 2023

Viewed by 948

Abstract

Bucket foundations, especially multi-bucket foundations, have become an alternative for large offshore wind turbines. Vertical responses of a single bucket are critical for the serviceability design of tripod or tetrapod bucket foundations. Centrifuge tests are conducted to investigate the responses of a single [...] Read more.

Bucket foundations, especially multi-bucket foundations, have become an alternative for large offshore wind turbines. Vertical responses of a single bucket are critical for the serviceability design of tripod or tetrapod bucket foundations. Centrifuge tests are conducted to investigate the responses of a single bucket under monotonic and symmetric cyclic loading in over-consolidated clay. The strength of clay is obtained by cone penetration tests. The monotonic vertical capacity measured in the centrifuge tests are compared with the finite element results, with errors less than 6%. The effects of the ratio of cyclic loading amplitude to vertical capacity (ranging between 0.37 and 0.64) and the number of cycles on the accumulation of vertical displacement and evolution of stiffness are explored. Simplified functions are proposed to predict the evolutions of dimensional and dimensionless stiffness. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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22 pages, 2758 KiB

Open AccessArticle

Dynamic Performance of Suspended Pipelines with Permeable Wrappers under Solitary Waves

by Youkou Dong, Enjin Zhao, Lan Cui, Yizhe Li and Yang Wang

J. Mar. Sci. Eng. 2023, 11(10), 1872; https://doi.org/10.3390/jmse11101872 - 26 Sep 2023

Cited by 1 | Viewed by 684

Abstract

Submarine pipelines are widely adopted around the world for transporting oil and gas from offshore fields. They tend to be severely ruined by the extreme waves induced by the natural disaster, such as hurricanes and tsunamis. To maintain the safety and function integrity [...] Read more.

Submarine pipelines are widely adopted around the world for transporting oil and gas from offshore fields. They tend to be severely ruined by the extreme waves induced by the natural disaster, such as hurricanes and tsunamis. To maintain the safety and function integrity of the pipelines, porous media have been used to wrap them from the external loads by the submarine environment. The functions of the porous wrappers under the hydrodynamic impact remain to be uncovered before they are widely accepted by the industry. In this study, a numerical wave tank is established with the immersed boundary method as one of the computational fluid dynamics. The submarine pipelines and their porous wrappers are two-way-coupled in terms of displacement and pressure at their interfaces. The impact from the solitary waves, which approximately represent the extreme waves in the reality, on the pipelines with different configurations of the porous wrapper is investigated. The results present significant protective functions of the wrappers on the internal pipelines, transferring the impact forces from the pipelines to the wrappers. The protective effects tend to be enhanced by the porosity and thickness of the wrappers. The influence of the pipeline configurations and the marine environment are then analysed. As for the front pipeline, an increase in the gap leads to a slight increase in the horizontal forces on both the wrapper and the pipeline, but a significant increase in the vertical forces. As for the rear pipeline, because of the shield function of the front pipeline, the velocity within the gap space and the forces on the pipes are decreased with the decrease in the gap size. The complex flow fields around the pipelines with wrappers are also illuminated, implying that the protection function of the wrapper is enhanced by the wave height reduction. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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21 pages, 8730 KiB

Open AccessArticle

Experimental Investigation on Particle Breakage Behavior of Marine Silica Sand under High-Stress Triaxial Shear

by Rong Chen, Tong Zhao, Zhiyong Wu, Dongxue Hao, Nan Xue and Chi Yuan

J. Mar. Sci. Eng. 2023, 11(9), 1825; https://doi.org/10.3390/jmse11091825 - 19 Sep 2023

Viewed by 805

Abstract

There is often obvious particle breakage for silica sand under high-stress, which will lead to the bearing capacity reduction and excessive settlement of the foundation. This paper focuses on the particle breakage characteristics of marine silica sand from the East China Sea under [...] Read more.

There is often obvious particle breakage for silica sand under high-stress, which will lead to the bearing capacity reduction and excessive settlement of the foundation. This paper focuses on the particle breakage characteristics of marine silica sand from the East China Sea under high-stress conditions. A series of conventional triaxial tests for silica sand, including consolidated drained (CD) and consolidated undrained (CU) shear tests, were conducted under the confining pressures in the range of 2–8 MPa to investigate the breakage rule during the shearing process. The developments of particle breakage index B_r with axial strain ε₁ and volumetric strain ε_v present hyperbolic and linear trends, respectively. A hyperbolic model was adopted to describe the relationship of B_r and ε₁ and the corresponding model parameters were obtained. The particle breakage index also has a good correlation with the input work per unit volume under various average stresses, regardless of the stress history. Furthermore, the relationship between the fractal dimension and the particle breakage was studied based on the particle size distribution curve. It is concluded that the fractal dimension increases in an up–convex hyperbolic trend with the increase of particle breakage index. The dividing radius for whether the silica sand particles exhibit the fractal features is determined as approximately 0.4 mm. This is anticipated to provide reference and supplementary test data for analyzing sand constitutive models/environments regarding particle crushing. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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16 pages, 6935 KiB

Open AccessArticle

Permeability of High Clay Content Dredger Fill Treated by Step Vacuum Preloading: Pore Distribution Analysis

by Wenchong Shan, Xiaoqing Yuan, Hui-e Chen, Xiaolin Li and Jinfeng Li

J. Mar. Sci. Eng. 2023, 11(9), 1714; https://doi.org/10.3390/jmse11091714 - 30 Aug 2023

Viewed by 732

Abstract

In this study, the step vacuum preloading method was used to reinforce high clay content dredger fill in the laboratory. The pore structures and permeability characteristics of dredger fill under different vacuum pressures were tested. The correlation between the pore structure parameters and [...] Read more.

In this study, the step vacuum preloading method was used to reinforce high clay content dredger fill in the laboratory. The pore structures and permeability characteristics of dredger fill under different vacuum pressures were tested. The correlation between the pore structure parameters and permeability coefficient was analyzed using the grey T’s correlation analysis method. The research results indicate that the pore ratio, large pore (the diameter with a range of 4–40 μm) content, and permeability coefficient of dredger fill decreased with the increase in vacuum pressures, but the decrease rates of the pore ratio were different at various sampling locations. The contents of micropores (the diameter with a range of <0.04 μm) and small pores (the diameter with a range of 0.04–0.4 μm) increased with the increase in vacuum pressure. The results of the correlation analysis showed that a large pore content had a strong correlation with the permeability coefficient and could be used to describe the permeability characteristics of soil. The research results can provide reference for the improvement of the reinforcement method and for the evaluation of the reinforcement effect of dredger fill in engineering practice. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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17 pages, 5701 KiB

Open AccessArticle

Bearing Characteristics of Tripod Bucket Foundation under Horizontal and Moment Load in Sand

by Xin Wang, Xue-Liang Zhao, Shu-Huan Sui, Zi-Bei Hu, Wen-Ni Deng and Qi-Ming Song

J. Mar. Sci. Eng. 2023, 11(8), 1631; https://doi.org/10.3390/jmse11081631 - 21 Aug 2023

Viewed by 750

Abstract

Based on a series of physical model tests and numerical simulations, the bearing characteristics of a tripod-bucket foundation are investigated. It is found that with the decrease in aspect ratio (L/D), the rotation center of the foundation will decrease, [...] Read more.

Based on a series of physical model tests and numerical simulations, the bearing characteristics of a tripod-bucket foundation are investigated. It is found that with the decrease in aspect ratio (L/D), the rotation center of the foundation will decrease, and the displacement model change from rotation to uplift. Characteristics of earth pressure on the buckets from both finite element analysis and model tests are studied, which is used to explain the failure mechanism for tripod-bucket foundations with different L/D. A revised method is proposed to estimate the moment bearing capacity of the tripod bucket foundation under horizontal and moment load. This method is thought to be more convenient and applicable in the practice. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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15 pages, 10504 KiB

Open AccessArticle

Undrained Triaxial Shear Tests on Hydrate-Bearing Fine-Grained Sediments from the Shenhu Area of South China Sea

by Ruchun Wei, Lele Liu, Chao Jia, Xiao Dong, Qingtao Bu, Yongchao Zhang, Changling Liu and Nengyou Wu

J. Mar. Sci. Eng. 2023, 11(8), 1604; https://doi.org/10.3390/jmse11081604 - 16 Aug 2023

Cited by 1 | Viewed by 907

Abstract

Changes in undrained shear strength are important to the stability analysis of hydrate reservoirs during natural gas hydrate production. This study proposes a prediction model of undrained shear strength of hydrate-bearing fine-grained sediments based on the critical state theory. Several consolidated undrained triaxial [...] Read more.

Changes in undrained shear strength are important to the stability analysis of hydrate reservoirs during natural gas hydrate production. This study proposes a prediction model of undrained shear strength of hydrate-bearing fine-grained sediments based on the critical state theory. Several consolidated undrained triaxial shear tests are conducted on hydrate-bearing fine-grained samples from the Shenhu area of the South China Sea. The effects of effective consolidation stresses and hydrate saturations on the undrained shear strength are investigated. The results show that the undrained shear strength increases linearly with increasing effective consolidation stress. When the hydrate saturation is greater than the effective hydrate saturation, the undrained shear strength significantly increases with increasing hydrate saturation. The undrained shear strength of hydrate-bearing fine-grained sediments is a two-parameter function of effective hydrate saturation and a void ratio. The instability risk of the hydrate reservoir under undrained conditions is greater than that of under-drained or partially drained conditions. Furthermore, low-porosity reservoirs face more shear strength loss from hydrate decomposition yet lower risk than high-porosity ones. These results can improve the understanding of mechanical properties of hydrate-bearing fine-grained sediments under undrained conditions. This study also has implications for the design of marine structures in areas with hydrate-bearing sediment. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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13 pages, 3821 KiB

Open AccessArticle

Pullout Bearing Capacity of End-Bearing Torpedo Anchors in Cohesive Soil Seabed

by Gang Li, Jinli Zhang, Jia Liu, Yu Xi and Honggang Kou

J. Mar. Sci. Eng. 2023, 11(8), 1548; https://doi.org/10.3390/jmse11081548 - 04 Aug 2023

Viewed by 854

Abstract

As a new type of deep-sea anchoring foundation, thetorpedo anchor has the characteristics of simple installation, low cost, and high bearing capacity. Compared with the torpedo anchor without an anchor wing, the end-bearing torpedo anchor forms pile end resistance using a bearing plate, [...] Read more.

As a new type of deep-sea anchoring foundation, thetorpedo anchor has the characteristics of simple installation, low cost, and high bearing capacity. Compared with the torpedo anchor without an anchor wing, the end-bearing torpedo anchor forms pile end resistance using a bearing plate, thus further improving its uplift bearing capacity. By conducting the pullout model test of torpedo anchors, we have compared and analyzed the effects of the pullout angle and bearing-plate radius on the bearing characteristics of T, EN3, EN4, and EC types of torpedo anchors. Based on the model test results, we established the V-H envelope of torpedo-anchor bearing capacity using the regression analysis method. The results show that when the displacement is small, the load-displacement curve of the torpedo anchor increases in an approximately linear mode, and the curve fluctuates and gradually entersa stable state with the gradual increase of the displacement. With the increasing pullout angle, the bearing capacity of the torpedo anchor increases first and then decreases. When the pullout angle is 45°, the torpedo anchor has the maximum bearing capacity. When the pullout angle is constant, the order of bearing capacity generated by different types of torpedo anchors is as follows: EC > EN4 > EN3 > T, and the bearing capacity rises with the increasing bearing-plate area. Through regression analysis, it is concluded that for the torpedo anchors of T, EN3, EN4, and EC types, the V-H envelope of bearing capacity shows an outward convex trend, and the determination coefficient reaches 0.930, indicating that the established V-H envelope is suitable for predicting the bearing capacity of torpedo anchors. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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21 pages, 7760 KiB

Open AccessArticle

Numerical Investigation of Uplift Failure Mode and Capacity Estimation for Deep Helical Anchors in Sand

by Chi Yuan, Dongxue Hao, Rong Chen and Ning Zhang

J. Mar. Sci. Eng. 2023, 11(8), 1547; https://doi.org/10.3390/jmse11081547 - 04 Aug 2023

Cited by 2 | Viewed by 989

Abstract

The uplift capacity of helical anchors is generally taken as the control condition for design in different applications, including transmission tower foundations and offshore structures. However, it is difficult to identify the failure surface for a deep helical anchor, which may result in [...] Read more.

The uplift capacity of helical anchors is generally taken as the control condition for design in different applications, including transmission tower foundations and offshore structures. However, it is difficult to identify the failure surface for a deep helical anchor, which may result in an incorrect assessment of uplift capability. This research proposes a new unified method to estimate the uplift capacity of deep single-helix and multi-helix anchors based on the investigation of failure mechanisms. The deep failure mode was identified by FEM analysis using a modified Mohr–Coulomb model considering the strain softening of sand, along with the coupled Eulerian–Lagrangian technique. Thereby, a simplified rupture surface is proposed, and the equations estimating the uplift capacity are presented by the limit equilibrium method. Two important factors—the lateral earth pressure coefficient and the average internal friction angle included in the equations—are discussed and determined. The comparisons with centrifugal tests verify the reasonability of the proposed method. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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20 pages, 10743 KiB

Open AccessArticle

Three-Dimensional Ultrasonic Reverse-Time Migration Imaging of Submarine Pipeline Nondestructive Testing in Cylindrical Coordinates

by Daicheng Peng, Fei Cheng, Xiaoyu She, Yunpeng Zheng, Yongjie Tang and Zhuo Fan

J. Mar. Sci. Eng. 2023, 11(7), 1459; https://doi.org/10.3390/jmse11071459 - 22 Jul 2023

Cited by 3 | Viewed by 976

Abstract

Submarine pipelines are a safe and energy-efficient mode of gas transport. However, due to the complex manufacturing process and harsh operating environment, submarine pipelines are subject to fatigue cracks under long-term cyclic loading. A comprehensive and high-precision characterization strategy for submarine pipelines can [...] Read more.

Submarine pipelines are a safe and energy-efficient mode of gas transport. However, due to the complex manufacturing process and harsh operating environment, submarine pipelines are subject to fatigue cracks under long-term cyclic loading. A comprehensive and high-precision characterization strategy for submarine pipelines can effectively prevent potential safety hazards and have significant economic and social repercussions. As a matter of fact, pipeline defects cannot be reliably detected with current traditional 2D methods. On the other hand, in ultrasonic testing, cylindrical geometry increases the complexity of the 3D wave field in the submarine pipeline space and significantly influences the accuracy of the detection results. In this paper, we put forward a novel method for 3D ultrasonic image testing that is suitable for cylindrical coordinates. In order to accurately simulate the ultrasonic signal received from pipelines, we generalize the 3D staggered-grid finite-difference method from Cartesian coordinates to cylindrical ones and simulate the full wave field in the 3D pipeline space. Then, signal processing is performed on the ultrasound simulation records, and 3D reverse-time migration imaging of submarine pipeline defects can be effectively achieved using the reverse-time migration method and cross-correlation imaging conditions. The results obtained from simulations and real field data show that the proposed method provides high-quality 3D imaging of defects in pipelines, taking into account multiple scattering and mode conversion information at the bottom of the defects. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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19 pages, 5940 KiB

Open AccessArticle

Ontology Framework for Sustainability Evaluation of Cement–Steel-Slag-Stabilized Soft Soil Based on Life Cycle Assessment Approach

by Chunyang Yu, Jia Yuan, Chunyi Cui, Jiuye Zhao, Fang Liu and Gang Li

J. Mar. Sci. Eng. 2023, 11(7), 1418; https://doi.org/10.3390/jmse11071418 - 14 Jul 2023

Cited by 1 | Viewed by 1049

Abstract

Steel slag has become a promising supplementary cementitious material for soft soil stabilization. However, there is a lack of research on the integrated assessment of cement–steel-slag-stabilized soft soils (SCSs) from the performance, environmental, and economic perspectives. In this study, an ontology framework for [...] Read more.

Steel slag has become a promising supplementary cementitious material for soft soil stabilization. However, there is a lack of research on the integrated assessment of cement–steel-slag-stabilized soft soils (SCSs) from the performance, environmental, and economic perspectives. In this study, an ontology framework for the sustainable evaluation of SCSs was developed based on the life cycle assessment (LCA) approach, which combined a knowledge base with semantic web rules to achieve an automated decision design for soft soil stabilization, considering comprehensive benefits. The ontology framework was applied to a marine soft soil stabilization case to verify its scientificity and practicability and to evaluate the influence of the fineness, carbonation degree, and substitution ratio of steel slag on the sustainability of SCSs. The results show that, when compared to pure-cement-stabilized soil (S-C), using 10% and 20% of fine steel slag carbonated for 18 h (FSS-C-18h) as cement substitutes can significantly reduce carbon emissions and costs while achieving a similar strength performance as S-C, demonstrating the feasibility of steel slag as a sustainable supplementary cementitious material for soft soil stabilization. Full article

(This article belongs to the Special Issue Engineering Properties of Marine Soils and Offshore Foundations)

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