Search

The ecological implications of deep-sea mining, particularly the considerable discharge of suspended sediments during operational processes, have attracted substantial concerns. In order to reveal the metal regeneration dynamics in the polymetallic nodule area of the western Pacific Ocean, ex-situ sediment disturbance experiments were conducted on a research vessel. After two levels of regulated stirring disturbance were exerted for half an hour, the concentrations of 12 dissolved metals and physicochemical parameters, including Eh and pH, were monitored continuously in the overlying water for three days. Porewater samples were also collected at the starting and ending time of each experiment to detect the change of dissolved metal profiles within the sediments. The findings revealed that the sediment disturbance led to fluctuations in the concentrations of metals in the overlying water, with manganese exhibiting the most pronounced change at a coefficient of 208%. The temporal patterns of dissolved metal concentrations demonstrated a coherent behavior among certain metals, such as Li, V, Co, Ni, Rb, Mo, and Cs, which displayed an overall increase, ultimately surpassing the initial concentrations in the overlying water. In line with this, the metal concentration profiles in the porewater were also elevated. Spearman correlation analysis confirmed the synchronized behavior of these metals. The results suggested that the metals mobility might be governed by physicochemical factors in the overlying water. Moreover, the sedimentary features, such as grain size composition, and the morphological state of metals in sediments played pivotal roles in the differential responses of metal groups to sediment disturbance across stations. Conversely, the disturbance intensity was found to have a relatively minor impact on the dissolved metal behavior. The findings from the ex-situ experiments provided critical insights for predicting metal regeneration related to deep-sea mining, which are expected to be validated through rigorous monitoring protocols during future in-situ mining trials. [ABSTRACT FROM AUTHOR]

Centrifugal slurry pumps are extensively applied in industrial industries such as power metallurgy, petrochemicals, deep-sea mining, and other industrial fields. The primary objective of this research is to assess how conveying settings and particle characteristics influence the 100SHL4147 slurry pump's collision and erosion properties. Firstly, the computational fluid dynamics–discrete element method (CFD-DEM) coupling model fully coupled particle–fluid co-flow numerical simulation interface is built by utilizing the C++ language and the results are proven with tests. Subsequently, the simulation examines the wear properties of different sections through which the flow passes in the 100SHL4147 centrifugal slurry pump. In addition, following theoretical guidance, the slurry pump impeller's wear resistance performance can be improved by adjusting design factors such as the intake edge location and the blade wrap angle. The results are as follows. It is recommended to replace the impeller promptly due to the findings that indicate that the entire blade's pressure surface is vulnerable to different degrees of erosion under high-concentration situations. When the particle size increased from 0.4 to 0.8 mm, the wear rate decreased by up to 15%, as fewer particles were transported, lowering the collision frequency. Conversely, smaller particles intensify component wear. Adjusting the blade wrap angle from 66° to 96° reduced impeller and volute wear by an estimated 20%, enhancing the durability but slightly decreasing the delivery capacity. Extending the blade's leading edge toward the intake improved the flow capacity, although it increased the wear frequency from one-third of the pressure surface to the trailing edge. [ABSTRACT FROM AUTHOR]

The safe and secure supply of strategic mineral resources is an important strategic need of China, and the extraction of mineral resources from the deep earth is an irreplaceable strategy for a long time in the future. To ensure the demand for mineral resources, the safe and efficient mining of high-stress hard rock is a major problem that must be solved in deep mining. Firstly, the technical challenges of deep high-stress hard rock mining and the transformative mining philosophy of "turning harm into benefit" was delineated. And a key engineering countermeasure to weaken the high-stress hard rock before mechanical rock breaking to achieve commercial mining was proposed. Next, the mechanism, characteristics and development status of contact and non-contact rock weakening methods were summarized, and the potentiality of these two types of rock weakening methods in the field of assisting mechanical breaking of high-stress hard rock was compared and analyzed. Finally, the safe and efficient continuous mining technology represented by mechanical rock breaking with thermal exfoliation damage weakening of deep high-stress hard rock was prospected. It provides useful guidance for the safe and secure supply of deep strategic mineral resources and the development of deep earth engineering. [ABSTRACT FROM AUTHOR]

The mechanization, greening and intelligent construction technology of the patio has become the main trend of technological development. This is also one of the key tasks to promote the high-quality development of metal mines. The mining of metal mines is gradually moving towards deeper areas, and the complexity of geological conditions such as high ground pressure, high ground temperature, and high-water pressure, as well as the uncertainty of the operating environment, are becoming increasingly prominent. These bring great difficulties and challenges to the construction of various raiserockhole projects serving mine production. The types of raiserockholes were comprehensively reviewed in metal mining, and the existing mechanical rock-breaking drilling processes for vertical raiserockhole, inclined raiserockhole, and cutting groove (blind raiserockhole) were analyzed. By analyzing the status and challenges faced by existing cutting groove drilling rigs and raise boring machine, the key technologies for intelligent drilling of cutting groove drilling rigs and raise boring machine have been analyzed from the aspects of efficient drilling, intelligent control, surrounding rock control, and intelligent equipment. In response to the insufficient one-time drilling capacity of existing raise boring machines for large diameter and high to medium section shafts, as well as the high deformation of fractured and weak surrounding rocks, which can easily lead to instability and collapse of the raiserockhole. A new construction technology for the integration of drilling and support with large diameter raise boring machines in poor strata has been proposed. Focusing on key technologies such as mechanical rock breaking and positive boring, full-section equipment intelligent boring, equipment matching and safe suspension, and the starting and dismantling of the raiserockhole boring machine, the research and development direction of the raiserockhole boring machine drilling technology has been analyzed. The aim is to provide a reference for the development of safe, efficient, green and intelligent construction technology for metal mine mining. [ABSTRACT FROM AUTHOR]

Blue economy has the potential to promote economic growth, improve livelihoods, and create jobs while protecting marine ecosystems. This research uses a comprehensive analysis of secondary data sources to assess various blue economy sectors, including maritime transport, fisheries, aquaculture, offshore renewable energy, marine tourism, marine biotechnology, and ocean mining. By examining the blue economy experiences of developed nations like the United States, Canada, Japan, Norway, and Australia, the study identifies the best SDG practices and strategic lessons applicable to Bangladesh. In the case of Bangladesh, the research focuses on the blue economy initiatives, opportunities, and challenges associated with the Sustainable Development Goals (SDGs). The blue economy and SDGs nexus in the context of Bangladesh demonstrates that out of 17 goals, 12 SDGs (SDG 1, SDG 2, SDG 3, SDG 7, SDG 8, SDG 9, SDG 11, SDG 12, SDG 13, SDG 14, SDG 16 and SDG 17) are linked with blue economy practices in Bangladesh. However, in the case of developed countries, only six SDGs (SDG 7, SDG 8, SDG 9, SDG 12, SDG 13, SDG 14) are connected to the blue economy because of the diversity of blue economy practices across the countries. Situated along the Bay of Bengal, Bangladesh has significant potential to utilize its marine resources for sustainable development. However, it faces challenges such as inadequate infrastructure, regulatory gaps, environmental risks, and limited technological advancements. The study thus emphasizes the need for integrated policy frameworks, stakeholder coordination, investments in sustainable infrastructure, public–private partnerships, technological innovation, and community engagement. [ABSTRACT FROM AUTHOR]

Many bioactive compounds are reported from marine organisms, which are significantly different from those found in terrestrial organisms regarding their chemical structures and pharmacological activities. Marine glycoproteins (MGs) have aroused increasing attention as a good nutrient source owing to their potential applications in medicine, cosmetics and food. However, there is a lack of a comprehensive study on MGs to help readers understand the current state of research on marine-derived glycoproteins. The current review compiles the recent progress made on the structures and functions of MGs with future perspectives to maximize their value and applications via bibliometric analysis methods for the first time. The current research on MGs appears mostly limited to the laboratory, with no large-scale production of marine glycoproteins developed. The sugar chains are bound to proteins through covalent bonds that can readily be cleaved leading to difficultly in their separation and purification. Health effects attributed to MGs include treatment of inflammatory diseases, as well as anti-oxidant, immune modulation, anti-tumor, hypolipidemic, hypoglycemic, anti-bacterial and anti-freeze activities. This review can not only deepen the understanding of the functions of MGs, but also lay an important foundation for the further development and utilization of marine resources. HIGHLIGHTS: Overview on isolation, structural and functional properties of marine glycoproteins (MGs) via bibliometric analysis methods for the first time. Marine glycoproteins (MGs) have various biological activities and potential health applications. glycoproteins from marine organisms (MGs) significantly enhanced anti-oxidant and anti-inflammatory activities. [ABSTRACT FROM AUTHOR]

AbstractThe projected increase in demand for some metals required for various industries, including transition to clean energy sources, shall force people to look for new deposits and the development of such deposits shall become progressively complicated. Arctic shelf is one of the promising mineral sources, but its areas are hardly explored and developed. The reasons include the absence of mining technologies that could ensure the efficient development of subsea solid mineral deposits. This study proposes a mining technology that enables transportation of minerals from the seabed to the water surface using the ice that covers the valuable mineral particles suspended by means of loosening and continuous supply of cooling agent to the submarine mining face. The technology implies formation of soil-ice bodies comprising an ice component with pores and mineral particles. The detailed study of the proposed technology and its application conditions included the development of a theoretical model of soil-ice bodies emersion from the seabed to the water surface with account of ice component melting. [ABSTRACT FROM AUTHOR]

During the retrieval process of the deep-sea mining vehicle (DSMV), the stability of the retrieval system is strongly influenced by the interaction between the vehicle body and the surrounding seawater due to the vehicle's complex shape and wave motion. Naturally, the negative side effects of significant changes in the vehicle's attitude and the water exit position can only increase retrieval's challenge. To investigate the characteristic of the flow field of the DSMV, this study employs the computational fluid dynamics method based on the Reynolds-averaged Navier–Stokes equations integrating the volume-of-fluid multiphase flow model with a fifth-order Stokes-wave model to explore the attitude and displacement changes of the vehicle during the water exit process in the ocean wave environment. The results indicate that the wave phase and lifting force are the major effect factors in the DSMV's water exit process. An appropriate lifting force under a specific wave phase can effectively reduce attitude changes and positional drift of the DSMV during water exit, thereby enhancing recovery efficiency and stability. [ABSTRACT FROM AUTHOR]

This study investigates the deflection and drag on flexible marine structures under steady-flow conditions and internal solitary waves (ISWs) using free-hanging risers as a representative example. We examine the relationship between the Cauchy number (Ca), buoyancy parameter (B), deflected height (hd), and effective length (le). Our findings reveal that flow fields influenced by ISWs closely resemble steady flow. This similarity enables the use of steady-flow analyses as a proxy in extreme motion studies of flexible marine structures. We also discover that an inclined configuration of flexible marine structures, such as free-hanging risers, diminishes the horizontal forces exerted by both steady currents and ISWs. Additionally, for both scenarios, increasing the weight of longer flexible marine structures is more effective than increasing stiffness in reducing deflection. The proposed method accurately predicts the deformation of flexible marine structures caused by ship motion in deep-sea mining and the movements of ocean risers with floating platforms. This finding is important for the design and optimization of these structures. [ABSTRACT FROM AUTHOR]

A novel model is proposed for analyzing high-concentration granular flow systems comprising equally sized spherical particles within vertical, long straight pipelines. This model is specifically tailored for simulating the vertical hydraulic transport of ore particles in marine mining projects. The proposed model treats the granular system akin to a pseudo-fluid and operates through three mechanisms. First, fluid characteristics of the granular system are derived from particle–particle collisions. Second, the resistance exerted by the pipe wall on the granular system is calculated based on the momentum loss of particles during particle–wall collisions. Third, the interaction between individual particles and the surrounding fluid is transformed into an interaction between the carrier fluid and the pseudo-fluid. Additionally, the present work develops a dedicated numerical format and iterative method for solving the one-dimensional two-fluid governing equations. The one-dimensional (1D) model notably enhances computational efficiency and facilitates accurate tracking of high-concentration particles over extended distances within straight pipelines. Notably, the proposed 1D model demonstrates a high degree of predictive accuracy when compared against experimental data as well as results from computational fluid dynamics and discrete element method simulations. [ABSTRACT FROM AUTHOR]

The double-row hydraulic sluicing model is widely used in deep-sea mining collecting systems. However, there has been limited research focusing on its flow contributions and the relationship with particle motions. In this paper, a double-row hydraulic sluicing collector with high pickup efficiency is designed. The flow characteristics, the mechanics of the flow field, and the movement of particles in the collector are analyzed in detail through numerical calculations and experiments. The flow contributions and the collecting mechanism are clearly highlighted through aspects such as the frequency of pressure fluctuations and flow-induced vortices. The high-speed jet rolls upward after hitting the ground, forming a high-pressure area on the ground. The upwelling in the collection area is generated by the combination of the high-pressure area and the upward rolling of fluid. Regarding the particles, it is observed that particle motion can be divided into two main stages, rapid acceleration, followed by slow deceleration. Some particles may fall back when rising. Additionally, the analysis of fluid forces on the particles indicates that drag force and pressure gradient force have significant influence on particle motion. [ABSTRACT FROM AUTHOR]

This article uses historical and ethnographic methods to examine the primarily East-Central European Interoceanmetal Joint Organization (IOM). I ask how and why the IOM has survived as an institution since its inception in 1987, working especially with the personal archive of Vratislav Kubišta. Kubišta was a metallurgist and former Deputy Director General at IOM who after retirement sought to develop a local deep-sea mining museum. This is a story about the work that archives do, but even more about how institutions maintain archives. I draw on recent work in the history and anthropology of time and archival practice to situate IOM's history and Kubišta's collection in narratives of ruin, the unbuilt, and the experience of multiple temporalities within spaces of resource speculation and anticipation. I suggest that IOM's history highlights the contingencies of resources in the temporality of indefinite pause, their attendant data, and scientific labor and life under the shifting political, economic, and scientific circumstances of the ongoing not-yet. In broadening the history of what is once more a hotly contested potential resource, this account speaks to the claims of contemporary would-be seabed miners, who frequently frame the practice in terms of innovation, urgency, and novelty. [ABSTRACT FROM AUTHOR]

This article critically examines the current benefit-sharing regime on the international seabed (the Area) and the proposed modalities for benefit-sharing. The United Nations Convention on the Law of the Sea contains few and vague rules on this issue. The only obligation is that benefit-sharing should be ‘equitable’ and the interests of developing States must be considered. To determine what may constitute equitable sharing the practice of other law of the sea legal regimes are examined and proposed distribution mechanisms are critically analysed. The article offers a unique perspective by trying to identify the scope of the vague equitable criterion for sharing or distributing benefits, rather than referring to it as a general goal or principle. Doing so, the article offers a practical account for the feasibility of different distribution modalities, which may yield new insights for institutional design to better deal with challenges in this well-researched but still unclear issue. [ABSTRACT FROM AUTHOR]

A dual-jet collecting device is highly efficient at picking up small-sized polymetallic nodules; however, its performance is not as effective for large nodules in deep-sea mining. To address this problem, numerical simulations have been conducted to thoroughly investigate the flow characteristics and particle motions during the collection of larger nodules. The collection performance of the enhanced device is analyzed across varying front jet velocities (Vf), suction pressures (Pout), and nozzle heights (h/d). The results reveal that increasing Vf improves the drag force and particle velocity in the jet impingement and upwelling zones, facilitating nodule lifting movement and transport. However, increasing Pout reduces the drag forces in these zones while increasing the particle velocity in the upwelling zone. A large Pout is not conducive to nodule initiation but has benefits for transport. Increasing h/d reduces the drag force in the anti-gravity direction in the jet impingement zone. The improved collecting device attains a pick-up efficiency that exceeds 80% for large-sized nodules when h/d < 1.3. The pick-up efficiency with suction pressure, which remains 40%, is higher than that without suction pressure when h/d > 1.3. The research findings may shed light on the design of more efficient dual-jet collection systems. [ABSTRACT FROM AUTHOR]

This activity leverages the use of a single case study to explain conflict mapping and find an optimal solution to the complicated challenges posed by the situation in Nauru, an island country that is now participating in seabed mining operations. In groups, students are given a chance to participate in two discussions: one within their respective groups and the other collectively as a class. In the ensuing discussions with the class, students have a glimpse into the complicated yet necessary efforts that a conflict situation demands from participants. Courses: Courses that are suited to this activity include conflict resolution and small group communication. Objectives: The activity shows students that a carefully developed conflict map is advantageous for understanding the many aspects of a disagreement and selecting the most optimal approach to communicating with seemingly opposing parties. The exercise teaches conflict resolution and promotes collective awareness by actively including every individual in the decision-making process. It also encourages reflection on the perspectives that are sometimes overlooked in classrooms based in the Global North and considers voices from marginalized populations that have limited possibilities to share their perspectives, particularly in nations in the Global South. [ABSTRACT FROM AUTHOR]

Mineral-rich hardgrounds, such as ferromanganese (FeMn) crusts and phosphorites, occur on seamounts and continental margins, gaining attention for their resource potential due to their enrichment in valuable metals in some regions. This study focuses on the Southern California Borderland (SCB), an area characterized by uneven and heterogeneous topography featuring FeMn crusts, phosphorites, basalt, and sedimentary rocks that occur at varying depths and are exposed to a range of oxygen concentrations. Due to its heterogeneity, this region serves as an optimal setting for investigating the relationship between mineral-rich hardgrounds and benthic fauna. This study characterizes the density, diversity, and community composition of macrofauna (>300 μm) on hardgrounds as a function of substrate type and environment (depth and oxygen ranges). Rocks and their macrofauna were sampled quantitatively using remotely operated vehicles (ROVs) during expeditions in 2020 and 2021 at depths above, within, and below the oxygen minimum zone (OMZ). A total of 3,555 macrofauna individuals were counted and 416 different morphospecies (excluding encrusting bryozoans and hydrozoans) were identified from 82 rocks at depths between 231 and 2,688 m. Average density for SCB macrofauna was 11.08 ± 0.87 ind. 200 cm−2 and mean Shannon-Wiener diversity per rock (H′[loge]) was 2.22 ± 0.07. A relationship was found between substrate type and macrofaunal communities. Phosphorite rocks had the highest H′ of the four substrates compared on a per-rock basis. However, when samples were pooled by substrate, FeMn crusts had the highest H′ and rarefaction diversity. Of all the environmental variables examined, water depth explained the largest variance in macrofaunal community composition. Macrofaunal density and diversity values were similar at sites within and outside the OMZ. This study is the first to analyze the macrofaunal communities of mineral-rich hardgrounds in the SCB, which support deep-ocean biodiversity by acting as specialized substrates for macrofaunal communities. Understanding the intricate relationships between macrofaunal assemblages and mineral-rich substrates may inform effects from environmental disruptions associated with deep-seabed mining or climate change. The findings contribute baseline information useful for effective conservation and management of the SCB and will support scientists in monitoring changes in these communities due to environmental disturbance or human impact in the future. [ABSTRACT FROM AUTHOR]

Against the backdrop of the United Nation’s recent adoption of the ‘BBNJ Agreement’ and the spotlight on the International Seabed Authority (ISA) regarding deep seabed mining, this article analyses area-based management tool (ABMT) provisions and processes under the BBNJ Agreement and ISA, using the draft Regional Environmental Management Plan for the northern Mid-Atlantic Ridge as a specific example. It explores potential interactions between the BBNJ Agreement and the ISA, and compares their ABMT processes, to understand how they could contribute to creating coherent ABMT networks in areas beyond national jurisdiction. It considers how the BBNJ Agreement’s objective for international cooperation and coordination with other instruments, frameworks, and bodies is envisaged, and could practically play out with the ISA, particularly in light of its ‘not undermine’ obligation. It suggests improvements to the ISA ABMT processes, based on the standards and procedures set by the BBNJ Agreement. [ABSTRACT FROM AUTHOR]

Managing deep-sea mining is challenging due to limited data on species and habitat distribution, hindering decision-making. In less-explored polymetallic nodule sites in the Indian Ocean, management approaches are deemed unfeasible due to a substantial lack of data. In this study, we aim to bridge the knowledge gap through a detailed analysis of the macrobenthos (fauna > 300 µm) obtained with two sampling gears (multi- and box corer) in potential impact, preservation, and reference zones in the Central Indian Ocean Basin. In total, 337 individuals were categorized into 106 morphospecies and 18 higher taxa. The lowest abundance was reported in the box corer. Nematodes and copepods dominated the macrobenthos community, whereas polychaetes and tanaidaceans were the more prevalent macrofaunal taxa. Carbohydrates and total organic carbon showed a notable positive correlation with polychaetes, isopods, and bivalves, indicating their influence on larger-sized taxa. Various functional traits, i.e., less motile, discretely motile, biodiffusors, and upward/downward conveyers, were dominant in the study area. The comparative analysis of multi- and box corer sampling reveals distinct patterns in macrobenthic diversity, emphasizing the importance of employing both gears for accurate functional analysis. The paper underscores the significance of including large meiofaunal taxa in macrofauna analyses for assessing deep-sea ecosystem functioning and services. Additionally, the findings contribute significantly to environmental baseline and impact assessment, a crucial aspect of sustainable management in a highly promising polymetallic nodule mining area, aligning with the goals of exploring. [ABSTRACT FROM AUTHOR]

With the utilization of the mineral resources of the international seabed area entering a new phase of exploitation, the international community’s concern for the protection of the marine environment in the international seabed area has also reached an unprecedented level. Regional Environmental Management Plans (REMPs), formulated by the International Seabed Authority (ISA), are considered as an important component of marine environmental protection in the deep seabed. However, REMPs are faced with challenges in practice under the background of deep-sea mining. In this work, we review the historical evolution of REMP, sort out the challenges faced by REMP from NWP to global and provide our suggestions to solve these issues. Specifically, the difficulties in the Northwest Pacific (NWP) REMP are mainly located in the lack of environmental scientific data. Meanwhile, from a global perspective, besides difficulties in local region, such as NWP, REMPs are facing more challenges, such as the arguments about the legal force of REMPs, conflicts between REMPs and the BBNJ Agreement, as well as absence of regulations for balancing exploitation and conservation. Focus on these challenges, suggestions are proposed including using the ISA to coordinate the application between REMPs and BBNJ Agreement and using the principle of scientific evidence to improve the regulations of REMPs. This work not only introduces a new insight for improving the framework system for the protection of the marine environment in the international seabed area, but also provides a reference for the solution to new challenges in the field of marine environmental protection. [ABSTRACT FROM AUTHOR]

The depths of the North Atlantic Ocean host a species-rich fauna providing heterogeneous habitats from thermal vent fields to cold-water coral reefs. With the increasing threat of destruction of deep-sea habitats due to human impacts, such as demersal fishing and the beginning of deep-sea mining, an analysis of the diversity and distribution of species is crucial for conservation efforts. Brittle stars occur in high biomasses, contributing to the biodiversity of the seafloor. Specimens were collected during several scientific expeditions to gain a more detailed insight into the brittle star diversity in the North Atlantic Ocean. An integrative approach to identify the species with DNA barcoding (mtCOI) in combination with morphological studies revealed 24 species. Most species have been previously identified in the North Atlantic, but sequences for 13 species are newly added to public repositories. Additionally, the MALDI-TOF-MS proteomic analysis was successfully applied for 197 specimens with known COI barcodes. Results are congruent with other molecular species delimitations demonstrating the functionality of proteomics for the identification of brittle stars. This dataset significantly expands our understanding of the taxonomic and genetic diversity of brittle stars and contributes to publicly available data. It emphasizes the importance of considering habitat heterogeneity for large scale patterns of biodiversity. [ABSTRACT FROM AUTHOR]

Barnacles have demonstrated adaptability to a range of habitats, spanning from shallow water to the deep sea. Given the harsh conditions present in hydrothermal vents, hydrothermal vent barnacles serve as the model organism for investigating the interplay between evolution and adaptability. In order to gain insights into barnacle adaptive characteristics, particularly within hydrothermal vents, we conducted a comprehensive analysis of the mitogenomes and transcriptome in a deep-sea barnacle (Neolepas marisindica), in comparison to its shallow-water related species. The mitogenomes with the same genetic skews and the non-synonymous/synonymous mutation ratios (Ka/Ks) of the mitogenomes indicate that the protein-coding genes (COIII, ND2, and ND6) of N. marisindica are under positive selection. Meanwhile, the functional annotation shows that distinctly positive selected orthologs in N. marisindica are predominately related to neural signal transduction, immunity, antiapoptotic, and energy metabolism. These results indicate that the mitogenomes and key genes found in transcriptomic analysis are under high-temperature and highpressure conditions, and which may contribute N. marisindica to have evolved to adapt to the extreme hydrothermal vent environments. The findings shed light on the mitogenome and transcriptome of N. marisindica, which lays a foundation for the in-depth understanding of the adaptation mechanism of sessile invertebrates to the deep-sea environment. [ABSTRACT FROM AUTHOR]

Ore collection devices are important for the collection of deep-sea polymetallic nodules. Based on the CFD-DEM solid–liquid two-phase flow coupling calculation method, this paper simulated the rise and transport phases of polymetallic nodules using the Coanda effect ore collection device. The validity of the numerical simulation method was confirmed through experimental testing. On this basis, the effects of different working and structural parameters on the collection rate were studied. The results indicate that the flow rate of the collection jet and the bottom clearance were the primary factors affecting the collection rate of the polymetallic nodules. An increase in the collection jet flow rate leads to a substantial rise in the collection rate of polymetallic nodules. Conversely, an increase in bottom clearance results in a decrease in the collection rate. A collection rate exceeding 90% can be achieved in both scenarios: a 10 mm bottom clearance with an 8 m/s collection jet flow rate, and a 30 mm bottom clearance with a 10 m/s collection jet flow rate. The collection nozzle slant angle has no substantial impact on the collection rate, and the recommended collection nozzle slant angle is 35° to reduce energy loss. [ABSTRACT FROM AUTHOR]

This paper reports the experimental results of the coupling response of a catenary flexible riser excited by both internal liquid–solid two-phase flow and the external shear current. The conveyed flow density ranges from 1000 to 1200 kg/m3, with velocity changing from 0 to 2.15 m/s. The vibration of the flexible riser was tested in the depth-averaged reduced velocity (Ur) range of 4.52–54.05. The experimental results indicate that only the in-plane response is excited by the internal liquid–solid flow when the riser is immersed in still water. As either the internal flow density (ρin) or velocity (uin) grows, the in-plane response is enhanced, resulting in the augmented fluctuations of pressure difference and top tension. In the presence of external flow, the out-of-plane response is also excited. The critical reduced velocity for mode transition becomes larger as either uin or ρin increases. Nonetheless, both the in-plane and out-of-plane responses are not sensitive to the internal flow when Ur is sufficiently high. Generally, the out-of-plane response is predominately contributed from the external flow, while the internal liquid–solid flow is the main contributor to the in-plane response at lower Ur. [ABSTRACT FROM AUTHOR]

In deep-sea mining engineering, accurately predicting the energy required per unit length of pipeline to transport a unit mass of solids (dimensionless specific energy consumption, DSEC) is crucial for ensuring energy conservation and efficiency in the project. Based on our previous work, we utilized the machine learning (ML) and the computational fluid dynamics (CFD)–discrete element method (DEM) method to study the transport characteristics and flow field variations of gradated coarse particles in inclined pipes (gradated particles refer to solid particles mixed in specific size and quantity ratios). First, we collect 1185 sets of data from 13 experimental literature, and after analyzing and processing them, an ensemble model based on four other ML models is developed. Both for pure substance particles (PS) and mixed particles (MP), the prediction accuracy of this ensemble model is relatively higher (PSs are spherical particles with uniform size and density, and MPs are particles with different shapes, sizes, and densities). Then, the CFD-DEM process and the operating conditions include low flow velocity with low volume concentration (2 m/s and 2.5%), low flow velocity with high volume concentration (2 m/s and 7.5%), and high flow velocity with low volume concentration (4 m/s and 2.5%). Under conditions of low flow velocity and low concentrations, as well as high flow velocity and low concentrations, the DSEC hardly changes with the variation of the pipe inclination angle. Under low flow velocity and high-concentration conditions, as the pipe gradually becomes vertical, the value of DSEC gradually increases. [ABSTRACT FROM AUTHOR]

Fifty-two years since the 1972 Declaration of the United Nations Conference on the Human Environment, deep seabed mining in areas beyond national jurisdiction remains controversial and widely discussed. In times of global demand for metals that are necessary to ensure energy transition and achieving a low-carbon society, the matter is becoming more convoluted. It is unclear if and what States will agree on as a common approach to deep seabed mining, or what relevance will be given to scientific evidence regarding any serious and irreparable harm to the marine environment it causes. This article examines the matter from a multidisciplinary approach and proposes that the new implementing agreement of the United Nations on the Law of the Sea on the conservation and sustainable use of marine biodiversity in areas beyond national jurisdiction offers an opportunity for strengthening environmental impact assessment obligations of deep seabed mining in these areas. [ABSTRACT FROM AUTHOR]

Deep-sea minerals are regarded as the most economically viable and promising mineral resource. Vertical hydraulic lifting represents one of the most promising methods for deep-sea mining lifting systems. To mitigate the potential for clogging due to the aggregation of particles in vertical pipe transport during deep-sea mining operations, this paper employs numerical simulations utilizing the computational fluid dynamics and discrete element method (CFD-DEM) model to investigate the swirling flow transportation of mineral particles. The characteristics of the swirling flow field and the motion law of double-size particles at different swirling ratios are investigated. The findings demonstrate that, in comparison to axial transport within the pipeline, the particle movement observed in swirling flow transport exhibits an upward spiral trajectory. This phenomenon facilitates the orderly movement of particles, thereby enhancing the fluidization of particles within the pipeline. An increase in the swirling ratio (SR) has a considerable impact on the velocity within the pipe. The tangential velocity distribution undergoes a gradual transition from centrosymmetric to non-centrosymmetric as the distance from the inlet increases. An increase in the SR results in an enhanced aggregation of particles at the wall, accompanied by a notable rise in the local particle concentration. The value of SR = 0.3 represents a critical threshold. When SR exceeds this value, the distribution of particles in the cross-section reaches a relatively stable state, rendering it challenging to further alter the distribution and concentration of particles, even if the SR is augmented. Furthermore, the maximum local particle concentration in the vicinity of the wall tends to be stable. These results provide valuable insights into vertical pipe swirling flow transport for deep-sea mining. [ABSTRACT FROM AUTHOR]

Data enhancement methods need to be carefully considered and studied for the widespread application of machine vision and deep learning in the mining field. Generative adversarial networks (GANs) prove successful at generating data. However, training a high-resolution image generation network depends on a large-scale dataset and takes a long time. For coal gangue detection, this paper proposes a stride-and-transpose-based progressive generative adversarial network (STP-GAN), which can achieve fast training on a few samples and generate high-resolution images in size of 10242. We employ stride convolutions, up-sampling, and average pooling to construct the model progressively and introduce noise and style optimization. We propose a hidden-layer-frozen progressive training scheme according to the model construction. Compared with other test GANs, STP-GAN generates more authentic and diverse images. The test results of advanced object detection models show that after the auxiliary training of STP-GAN, the mean average precision and average recall of coal–gangue detection are increased by up to 6.92% and 20.39%, respectively. The proposed method can effectively improve the accuracy of coal–gangue detection through data optimization. [ABSTRACT FROM AUTHOR]

The deep-sea mining lift pump is one of the pivotal components in deep-sea mineral transportation systems and its internal flow is very complex; consequently, unraveling its unsteady flow behavior pattern holds immense practical value. This study adopts numerical methods to analyze the time-averaged distribution characteristics of the internal flow field in mining lift pumps, as well as the flow field's pulsation intensity distribution characteristics, the vortex's spatiotemporal evolution process in both moving and static cascades, and the time- and frequency-domain pulsation characteristics of internal pressure in each flow passage component under four different flow conditions are also investigated. The hydraulic properties of mining lift pumps under these four different conditions are also evaluated, and the outcomes are benchmarked against those of numerical predictions. Our findings reveal that the interplay between impeller blades and guide vanes significantly influences the pump's flow characteristics, with the pump's unsteady flow influencing its hydraulic properties. Experimental validation of this system confirms that the pump under study is in line with design specifications in terms of hydraulic properties. The method validation test on the prototype pump shows that the SST k-ω model is capable of successfully forecasting instability in the flow features of deep-sea mining lift pumps. These results will serve as a theoretical reference for regulating the flow state inside deep-sea mining lift pumps. [ABSTRACT FROM AUTHOR]

Deep-sea hydraulic collection is a key technology for seabed mineral resource extraction, offering higher efficiency and environmental protection compared to other collection methods. However, due to their complex characteristics, the suction properties and influencing factors of polyhedral particles in hydraulic suction collection remain elusive. This study utilized dimensionless methods and conducted experiments to analyze the flow characteristics in cone-shaped collection hoods and the distribution of suction force on polyhedral particles, and researched the effect of various parameters, such as Φ, H/R, R/S, and H/dp (referring to the nomenclature given in the last part of this paper), on the suction force coefficients of polyhedral particles based on the suction force coefficients of spheres by acquiring the suction coefficient ratio (kc). The results indicate the following: (1) the presence of suction and coherent vortices in the horizontal positions of 0.1R to 0.2R within the central region, which move with changes in pump suction or cove height, benefiting particle collection; (2) the particle suction force (Fd) decreases with increasing sphericity (Φ), with a more pronounced decline in high-speed flow fields, exhibiting two peaks and one trough in the Fd curve within the hood's flow field; (3) the kc generally increases with decreasing Φ at the same collection position, showing increasingly stable fluctuations, and kc is sensitive to surrounding flow velocities with a rapid growth trend at higher speed, revealing that the suction coefficient (Cd) of polyhedral particles is significantly larger than that of spherical particles with increasing flow speed in high-speed flow fields; (4) Fd decreases with increasing H/dp, with a noticeable slowdown when H/dp exceeds 3.5. This study reveals the force characteristics and influencing factors of non-spherical coarse particles in hydraulic suction collection flow fields, providing insights for the development of collection technologies and equipment for deep-sea solid mineral resources, particularly irregular coarse particles. [ABSTRACT FROM AUTHOR]

Ore collection is very important in deep-sea mining for seafloor massive sulfide (SMS). In view of the characteristics of SMS ores produced by mechanical crushing, which contain coarse particles and a wide particle size distribution, in-depth research on the collection process with a device combining a rotary crushing head and a flat suction mouth was conducted. In this paper, solid–liquid two-phase flow in the hydraulic collection process with a drum rotation is carried out using the computational fluid dynamics-discrete element method (CFD-DEM), and the flow field characteristics and particle motion characteristics are analyzed. The results indicate that particles with a maximum diameter of 20 mm can be effectively collected when the suction velocity is 3 m/s. The collection process of SMS mainly goes through three stages: particle disturbance start-up, partial particle influx, and stable collection. In addition, the appropriate drum speed facilitates the collection of SMS ore. Finally, the correctness of the numerical method was assessed using similarity experiments. This work can be used to guide the design of underwater mining equipment. [ABSTRACT FROM AUTHOR]

REE-rich mud under the seabed at a 5500–5700 m water depth around Minamitorishima island and polymetallic nodules buried in the deep seabed are very promising and attractive to explore and develop. REEs are critical to develop due to the recent paradigm shift to renewable energies based on green technologies. Numerical analysis using a one-dimensional drift–flux model for gas–liquid–solid three-phase flow and gas–liquid two-phase flow was conducted to examine the characteristics of an air-lift pumping system for mining these mineral resources. Empirical equations of REE-rich mud and the physical properties of polymetallic nodules around Minamitorishima island were utilized in the analysis. As a result, the characteristics, i.e., the performance of the system, were clarified in three cases: REE-rich mud, polymetallic nodules, and both. The time transient, i.e., the unsteady characteristics of the system, was also shown, such as the start-up and feeding slurry with REE-rich mud and polymetallic nodules. The findings from the unsteady characteristics will be useful in considering the operation of a real project or a commercial system in the future. [ABSTRACT FROM AUTHOR]

Ferromanganese crusts are mineral resources distributed in the planet's oceans. These deep-sea minerals stand out for their abundance and diversity of metals, with Mn and Co being the most abundant elements. These minerals are a good alternative to diversify the extraction of elements, which today are found at low grades on the Earth's surface. For the co-processing of ferromanganese crusts to recover Co and Mn, there are few studies. These generally worked with the use of a reducing agent, and in many cases previous roasting processes. In the present investigation, two ferromanganese crusts that were collected from two seamounts in the central eastern Atlantic Ocean were characterized. Subsequently, these crusts were leached in an acid-reducing medium, adding steel waste (slag) with 99.73% Fe3O4 and 0.27% metallic iron from the steel industry as a reducing agent. Acid-reducing processes have previously been shown to yield high and rapid recoveries of Co and Mn from seabed minerals. However, there is no previous study using smelting slag as a reducing agent for the treatment of ferromanganese crusts. The best results of this research were obtained when working at 60 C, achieving joint extractions of Co and Mn of ~80% and ~40%, respectively, in 10 min. In addition, the process residues were analyzed, and the formation of contaminating elements or the precipitation of Co and Mn species was not observed. [ABSTRACT FROM AUTHOR]

Efficient mineral hydraulic collection is a key issue in the mining of deep-sea minerals, where the collection efficiency is related to the lifted fluid velocity and the mineral particle velocity. In this paper, a robust control contraction metric (RCCM)-based tube model predictive control (Tube-MPC) for efficient mineral hydraulic collection is proposed. Firstly, a simplified control model is designed with empirical formula of hydrodynamic forces to avoid the computational burden in solution of the fluid equations. Secondly, a nonlinear programing problem (NLP) for efficiency optimization is formulated to calculate the nominal control law and the optimal state. To address external disturbance and model mismatch from the simplified model, a robust control contraction metric is utilized to calculate the feedback control law to track the optimal state. Finally, numerical simulations and experiments are conducted to verify the mineral hydraulic collection performance of the control strategy. [ABSTRACT FROM AUTHOR]

The western Pacific seamount area is abundant in both biological and mineral resources, making it a crucial location for international investigation of regional seabed resources. An essential stage in comprehending and advancing seamounts is gaining knowledge about the distribution characteristics and laws governing the seabed substrate. Deep-sea geological sampling is challenging because of the intricate nature of the deep-sea environment, resulting in increased difficulty in identifying and evaluating substrates. This study addresses the aforementioned issues by utilizing in-situ video footage obtained from the "Jiaolong" manned deep submersible and shipborne deep-water multibeam data. This data is used as a foundation for constructing a Western Pacific seamount areas substrate classification point set. Additionally, the paper introduces the mRMR-XGBoost substrate classification model. Substrate categorization in deep sea and mountainous regions has been successfully accomplished, yielding a classification accuracy of 92.5%. The classification experiments and box sampling results demonstrate that the mRMR-XGBoost substrate classification model proposed in this paper can efficiently use acoustic and optical data to accurately divide the substrate types in seamount areas, with better classification accuracy, when compared with commonly used machine learning models. It has a significant application value and the best classification effect on the two types of substrates: nodules and gravel substrates. [ABSTRACT FROM AUTHOR]

In a previous publication in IJMCL, the author discussed a case of interference by environmental activists with the operations of a deep sea mining contractor in May 2021. While concluding that the actions could be considered unlawful, one of the most important findings was that adequate enforcement and effective remedies are mostly lacking. In November 2023, protest actions by Greenpeace from a Dutch-flagged vessel against deep sea mining activities resulted in media attention and a response by the International Seabed Authority (ISA), and led to a decision by an Amsterdam district court. This article examines the legal issues arising from both the ISA response and the Dutch court decision. [ABSTRACT FROM AUTHOR]

Particle distribution, wear failure, and particle passage performance in a two-stage mixed-transported pump are investigated by coupling computational fluid dynamic (CFD) and discrete element method (DEM). Results exhibit good agreement with the experimental data. The velocity and trajectory of a 10 mm particle are examined under three different concentrations. Consequently, the relationship between particle motion and the wear on the impeller and volute is revealed. The results indicate that low-speed particles lead to particle packing at the inlet of the first stage. The force variation of particles is closely related to the number of collisions with the wall. The wear on the suction side of the second-stage impeller and the second-volute wall are significantly less than that on the first-stage. Finally, the particle passage coefficient P is defined, demonstrating that the particle passage performance of the second-stage pump is better than that of the first-stage. [ABSTRACT FROM AUTHOR]

The Clarion–Clipperton Fracture Zone (CCFZ) in the eastern central Pacific Ocean is the world's largest area for potential deep‐sea polymetallic nodule mining and is attracting increased scientific and commercial interest. Recent studies indicate that biogenic magnetite, generated intracellularly by magnetotactic bacteria (MTB), can carry a biogeochemical remanent magnetization in polymetallic nodules, although whether biogenic or physical‐chemical processes are responsible for nodule formation remain poorly constrained. Here, we report a combination of magnetic, electron microscope and geochemical analyses on seafloor surface sediments from the eastern CCFZ to understand the spatial distribution of biogenic magnetite and possible relationships between MTB and polymetallic nodules. Experimental results indicate that sedimentary magnetic minerals from the northern and southern regions are dominated by detrital (eolian loess and volcanic material) and biogenic magnetic minerals (magnetosomes), respectively. Sediments from the intermediate region contain both detrital and biogenic magnetic minerals. Quantitative first‐order reversal curve‐principal component analysis indicates that biogenic magnetite has the highest concentration in the intermediate CCFZ region, coincident with the highest polymetallic nodule density. Combined with previous research, we speculate that MTB growth on the CCFZ seafloor is driven mainly by local redox conditions. Manganese nodule surfaces are rich in organic biofilms, which results in a relatively thick oxic‐anoxic transition zone in high‐abundance manganese nodule regions, which generates an optimal microenvironment for both MTB growth and magnetite biomineralization. This study provides new clues for understanding the ecological distribution of MTB and the biogeochemical remanent magnetization recorded by biogenic magnetite in deep‐sea sediments. Plain Language Summary: Polymetallic nodules are an important seafloor resource because they contain economically important minerals (e.g., Ni, Co, and Mn) that are not common on land. Hence, there is increased economic and scientific interest in understanding the formation mechanisms of these materials. Several studies indicate that biogenic magnetite crystals produced by magnetotactic bacteria (MTB) occur within polymetallic nodules. Testing the relationship between MTB abundance and polymetallic nodule distribution can help to better understand how these materials formed. Here, we study seafloor sediments from the Clarion‐Clipperton Fracture Zone (CCFZ) and find that they mainly contain biogenic and detrital magnetic minerals. Detrital magnetic minerals come from volcanic chains and eolian dust, while biogenic magnetite forms within bacterial cells. We find that increased biogenic magnetite abundance coincides with higher polymetallic nodule occurrences in the CCFZ. This implies that MTB activity may play a significant role in the formation and growth of polymetallic nodules. Key Points: Biogenic and detrital magnetic minerals are quantified in seafloor surface sediments from the Clarion–Clipperton Fracture ZoneBiogenic magnetite concentrations and polymetallic nodule density are increased in the central Clarion–Clipperton Fracture ZonePolymetallic nodule growth likely produced reducing, organic‐rich microenvironments suitable for magnetotactic bacteria [ABSTRACT FROM AUTHOR]

The particle plume, a ubiquitous particle–fluid coupled phenomenon in tailing discharge from deep-sea mining, undergoes suspension and diffusion over distances transportation. Our study is motivated by predicting plume dispersion patterns driven by different initial momentums, relying on understanding complex fluid–particle interaction mechanics. To consider irregular particle shapes and discrete effects, a discrete element method and large-eddy simulation coupled model is established in our in-house solver to simulate particle plumes and investigate flow characteristics from a Lagrangian perspective. The influence of the initial incident velocity W0 on particle flow regimes, movement patterns, velocity, concentration, Reynold shear stress, fluid–particle interactions, and energy budget is explored. The results show that a counter-rotating vortex pair forms in the initial stage, with ambient fluid entrainment inducing coherent vortex splitting into numerous vortex filaments, causing significant radial diffusion. Plume transportation begins with rapid settling, followed by a decrease to a roughly constant level. Increasing W0 enhances the particle velocity, allowing plumes to advance faster. This results in particle diffusion rate and concentration dilution rate increasing with decreasing W0. Away from the nozzle centerline, negative axial velocity magnitudes increase as W0 decreases, prompting particle radial diffusion. Additionally, for cases with low W0, significant particle concentration in regions far from the nozzle dampens pulsatile velocity, resulting in decreased Reynolds stress with decreasing W0. Notably, despite the complexity of particle–fluid interactions in plumes, the conversion of initial gravitational potential energy into particle and fluid kinetic energy is limited across all W0. [ABSTRACT FROM AUTHOR]

Valettietta Lincoln & Thurston, 1983 (Amphipoda: Alicelloidea) is an infrequently sampled genus of scavenging amphipod, with a known bathymetric range from 17–5467 m encompassing a variety of habitats from anchialine caves to abyssal plains. Molecular systematics studies have uncovered cryptic speciation in specimens collected from the abyssal Pacific, highlighting uncertainty in the description of Valettietta anacantha (Birstein & Vinogradov, 1963). Here, we apply an integrative taxonomic approach and describe two new species, Valettietta trottarum sp. nov. and Valettietta synchlys sp. nov. collected at abyssal depths in the Clarion-Clipperton Zone, Pacific Ocean. Both species can be distinguished by characters of the gnathopods, uropod 3, and the inner plate of the maxilliped. Further, molecular phylogenetic analyses of two mitochondrial (16S rDNA and COI) and two nuclear (Histone 3 and 28S rRNA) regions found both new species to form well-supported clades and allowed us to re-identify previously published records based on genetic species delimitation. The biogeography of Valettietta is discussed in light of these re-evaluated records, and a new taxonomic key to the genus is provided. These new taxa highlight the strength of applying an integrated taxonomic approach to uncover biodiversity, which is critical in regions being explored for potential industrial purposes. [ABSTRACT FROM AUTHOR]

The article examines how space mining represents an extension of the extractivist paradigm rather than the beginning of a new era of resource abundance. Topics discussed include the historical continuity of resource frontiers, the concept of Cheap Nature in relation to space resources, and the geopolitical dynamics surrounding space resource exploitation.

Submarine hydrate mining can trigger geological disasters, including submarine landslides and seafloor subsidence due to excess pore pressure and weakened layers, which may potentially lead to the reactivation of faults and increased seismic activity. However, current research encounters challenges in assessing geotechnical issues associated with long-term and large-scale production from well grids located in sloped areas. Limited by the complexity of the hydrate sediment, a multifield coupled numerical model of hydrate slope in the Shenhu area was established. Utilizing the modified Mohr–Coulomb model as the constitutive model for hydrate-bearing sediments to track the dynamic reduction in strength and employing the shear strength method to assess submarine slope stability, a series of depressurization strategies are applied to evaluate the risks associated with submarine landslides and seafloor subsidence. Results show that the hydrate dissociation tends to stagnate after a period of mining. The strength of the hydrate decomposed area is severely reduced, and a volume deficit occurs in this area, causing formation displacement. The peripheral region of the decomposed area is compacted by high stress, resulting in a serious decrease in permeability and porosity, which limits the continued decomposition of hydrates. The large-scale submarine landslides with hydrates decomposition will not appear in this block. However, several meters' seafloor subsidence over a wide range risks engineering safety significantly. The amount of seafloor subsidence in the first 50 days is approximately half of the final settlement. A higher production pressure drop can speed up the recovery rate while resulting in more significant seafloor subsidence and slippage. Therefore, the balance between mining speed and formation stability needs more research work. [ABSTRACT FROM AUTHOR]

Vertical pipes are a significant component of deep-sea mining hydraulic lifting systems, frequently stretching up to thousands of meters. This article employs the coupling approach of computational fluid dynamics for the liquid phase and the Discrete Element Method for the particle phase (CFD-DEM) to simulate solid–liquid two-phase flow in a vertical pipeline, utilizing a scaled vertical lift pipeline model as the study object. By adjusting the conveying parameters and structural factors, the lifting performance of particles and the two-phase flow characteristics under various operating circumstances are examined, and the veracity of the simulation is validated by experimental techniques. The findings reveal that the lifting of particles is impacted by both the conveying parameters and the structural factors. The increase in flow rate can effectively improve the distribution of particles in the pipeline and enhance the followability of particles. The disturbance created by the collision and mixing of particles induced by the change in particle concentration has a tremendous impact on the velocity distribution of the two-phase flow in the pipeline and the pressure distribution of the pipe wall. In addition, there is an ideal lifting flow corresponding to various particle concentrations, which may improve the particle dispersion. The outcome of this research has a certain reference relevance for the selection of the parameters of deep-sea mining lifting systems in the future. [ABSTRACT FROM AUTHOR]

Flexible pipe is one of the most important types of equipment applied in the deep-water development of oil and gas and deep-sea metal mining. The carcass of an unbonded flexible pipe with a typical interlocked structure prevents buckling failure under external hydrostatic pressure. The process and principle of carcass layer deformation are described, and a three-dimensional finite element model with solid-shell elements is developed to simulate the cold forming process of a metal strap subjected to a series of rollers. The deflection and deformation behavior in the bend-rolling and interlocking process are investigated, and the residual stress due to deformation is calculated. Taking the carcass layer of a 4-inch internal diameter flexible pipe as an example, a three-dimensional finite element model of the carcass layer loaded with external hydrostatic pressure is developed. The buckling collapse of the carcass layer is evaluated considering different initial imperfections, including residual stress. The results show that the critical pressure can be 60% less than under ideal conditions when the geometric imperfection, material nonlinearity and residual stress due to deformation are considered, which indicates that the effect of residual stress on buckling collapse cannot be ignored. The numerical model and results provide an efficient method and basis for nonlinear buckling analysis and a collapse-resistant unbonded flexible pipe design for industry. [ABSTRACT FROM AUTHOR]

AbstractHorizontal wells have the advantages of high production, considerable access to reserves, and effective sand production control; thus, they are potential well types for hydrate exploitation. In the process of hydrate mining, the decomposition of hydrate will cause the deterioration of the mechanical properties of the reservoir, which may induce submarine landslides, especially in the case of multiple horizontal wells, and the risk of submarine landslides is further increased. Therefore, it is necessary to study the influence of the horizontal well pattern adopted for hydrate mining on the stability of submarine slopes. First, a triaxial mechanical experiment of gas hydrate-containing sediments was carried out, and the mechanical parameters of the hydrate-containing sediments were obtained. Second, a thermal-fluid-solid multifield coupling model considering the hydrate phase transition during the production process was established. Finally, on the basis of the finite element strength reduction method, a slope stability evaluation model for hydrate extraction from a horizontal well pattern was established, and the influence of hydrate extraction from horizontal wells on the stability of submarine slope was analyzed. The results show that the peak strength, elastic modulus and cohesion of gas hydrate-containing sediments increase with increasing hydrate saturation. In the process of hydrate exploitation via horizontal wells, with the reduction in well spacing and the increase in the number of production wells, the risk of slope instability increases. Wells positioned along the slope strike are more conducive to slope stability than those positioned perpendicular to the slope strike. The slope stability increases gradually as the slope dip decreases. When the number of wells is the same, the slope stability increases gradually with increasing well spacing and production pressure. [ABSTRACT FROM AUTHOR]