Experimental investigation of the inhibition of deep-sea mining sediment plumes by polyaluminum chloride

Deep-sea sediment disturbance may occur when collecting polymetallic nodules,resulting in the creation of plumes that could have a negative impact on the ecological environment.This study aims to investigate the potential solution of using polyaluminum chloride(PAC)in the water jet.The effects of PAC are examined through a self-designed simulation system for deep-sea polymetallic nodule collection and sediment samples from a potential deep-sea mining area.The experimental results showed that the optimal PAC dose was found to be 0.75 g/L.Compared with the test conditions without the addition of PAC,the presence of PAC leads to a reduction in volume,lower characteristic turbidity,smaller diffusion velocity,and shorter settling time of the plume.This indicates that PAC inhibits the entire development process of the plume.The addition of PAC leads to the flocculation of mm-sized particles,resulting in the formation of cm-sized flocs.The flocculation of particles decreases the rate of erosion on the seabed by around 30%.This reduction in erosion helps to decrease the formation of plumes.Additionally,when the size of suspended particles increases,it reduces the scale at which they diffuse.Furthermore,the settling velocity of flocs(around 10^(-2) m/s)is much higher that of compared to sediment particles(around 10^(-5) m/s),which effectively reduces the amount of time the plume remains in suspension.

Integrated biomarker response to assess toxic impacts of iron and manganese on deep-sea mussel Gigantidas platifrons under a deep-sea mining activity scenario

Deep-sea mining activities can potentially release metals,which pose a toxicological threat to deep-sea ecosystems.Nevertheless,due to the remoteness and inaccessibility of the deep-sea biosphere,there is insufficient knowledge about the impact of metal exposure on its inhabitants.In this study,deep-sea mussel Gigantidas platifrons,a commonly used deep-sea toxicology model organism,was exposed to manganese(100,1000μg/L)or iron(500,5000μg/L)for 7 d,respectively.Manganese and iron were chosen for their high levels of occurrence within deep-sea deposits.Metal accumulation and a battery of biochemical biomarkers related to antioxidative stress in superoxide dismutase(SOD),catalase(CAT),malondialdehyde(MDA);immune function in alkaline phosphatase(AKP),acid phosphatase(ACP);and energy metabolism in pyruvate kinase(PK)and hexokinase(HK)were assessed in mussel gills.Results showed that deep-sea mussel G.platifrons exhibited a high capacity to accumulate Mn/Fe.In addition,most tested biochemical parameters were altered by metal exposure,demonstrating that metals could induce oxidative stress,suppress the immune system,and affect energy metabolism of deep-sea mussels.The integrated biomarker response(IBR)approach indicated that the exposure to Mn/Fe had a negative impact on deep-sea mussels,and Mn demonstrated a more harmful impact on deep-sea mussels than Fe.Additionally,SOD and CAT biomarkers had the greatest impact on IBR values in Mn treatments,while ACP and HK were most influential for the low-and high-dose Fe groups,respectively.This study represents the first application of the IBR approach to evaluate the toxicity of metals on deep-sea fauna and serves as a crucial framework for risk assessment of deep-sea mining-associated metal exposure.

Multiparameter Numerical Investigation of Two Types of Moving Interactions Between the Deep-Sea Mining Vehicle Track Plate and Seabed Soil:Digging and Rotating Motions

To ensure the safe performance of deep-sea mining vehicles(DSMVs),it is necessary to study the mechanical characteristics of the interaction between the seabed soil and the track plate.The rotation and digging motions of the track plate are important links in the contact between the driving mechanism of the DSMV and seabed soil.In this study,a numerical simulation is conducted using the coupled Eulerian–Lagrangian(CEL)large deformation numerical method to investigate the interaction between the track plate of the DSMV and the seabed soil under two working conditions:rotating condition and digging condition.First,a soil numerical model is established based on the elastoplastic mechanical characterization using the basic physical and mechanical properties of the seabed soil obtained by in situ sampling.Subsequently,the soil disturbance mechanism and the dynamic mechanical response of the track plate under rotating and digging conditions are obtained through the analysis of the sensitivity of the motion parameters,the grouser structure,the layered soil features and the soil heterogeneity.The results indicate that the above parameters remarkably influence the interaction between the DSMV and the seabed soil.Therefore,it is important to consider the rotating and digging motion of the DSMV in practical engineering to develop a detailed optimization design of the track plate.

Deep-sea rock mechanics and mining technology:State of the art and perspectives

The review covers the development and the state of the art in deep-sea mining rock mechanics,equipment and challenges.It begins by introducing the significance of deep-sea mining,the types and geographical distribution of deep-sea resources.Section 2 reviews the mechanical properties and fracture mechanism of seabed and related continental rocks,which contributes to the advancement of relevant technologies and theories.Deep-sea mining systems developed by coastal countries are presented in Section 3.Seabed mineral collection systems are critically assessed in Section 4.Subsea mining vehicle is reviewed by walking mechanism and controlling system in Section 5.In Section 6,the development of subsea lifting system is detailed by dividing it into hydraulic and pneumatic lifting modes,and some technical problems in the lifting system are described.An in-depth description of surface support systems is presented in Section 7,which includes the deep-sea mining ship,dynamic positioning system,heave compensation system,launch and retrieval system,mineral disposing system as well as the storage and transferring systems.Section 8 discusses the challenges in the deep-sea mining,in terms of natural occurrence conditions,international legal framework and cooperative mining,environmental protection and economic benefits,etc.Finally,a brief summary and some aspects of prospective research are presented in Section 9.

System Identification and Parameter Self-Tuning Controller on Deep-Sea Mining Vehicle

System identification is a quintessential measure for real-time analysis on kinematic characteristics for deep-sea mining vehicle, and thus to enhance the control performance and testing efficiency. In this study, the system identification algorithm, recursive least square method with instrumental variables(IV-RLS), is tailored to model ‘Pioneer I’, a deep-sea mining vehicle which recently completed a 1305-meter-deep sea trial in the Xisha area of the South China Sea in August, 2021. The algorithm operates on the sensor data collected from the trial to obtain the vehicle’s kinematic model and accordingly design the parameter self-tuning controller. The performances demonstrate the accuracy of the model, and prove its generalization capability. With this model, the optimal controller has been designed, the control parameters have been self-tuned, and the response time and robustness of the system have been optimized,which validates the high efficiency on digital modelling for precision control of deep-sea mining vehicles.

Blockage of the Deep-Sea Mining Pump Transporting Large Particles with Different Sphericity

The present study aims to plumb blockage of the deep-sea mining pump transporting large particles with different shapes. A numerical work was performed through combining the computational fluid dynamics(CFD) technique and the discrete element method(DEM). Six particle shapes with sphericity ranging from 0.67 to 1.0 were selected. A velocity triangle is built with the absolute, relative, and circumferential velocities of particles. Velocity triangles with absolute velocity angles ranging from 90° to 180° prevail in the first-stage impeller. With declining sphericity, more particles follow the velocity triangle with absolute velocity angles ranging from 0° to 90°, which weakens the ability of particles to pass through the flow passage. Furthermore, the forces acting on the particles traveling in the impeller passage are analyzed. Large particles, especially non-spherical ones, suffer from high centrifugal force and therefore move along the suction surface of the impeller blades. Non-spherical particles undergo great drag force as a result of large surface area. The distribution of drag force angles is featured by two peaks, and one vanishes due to blockage.As particle sphericity declines, both magnitude and angle of the pressure gradient force decrease. Variation of the drag force and the pressure gradient force causes clockwise deflection of the centripetal force, resulting in deflection and elongation of particle trajectory, which increases the possibility of blockage.

Instability Assessment of Deep-Sea Risers Under Parametric Excitation

This study deals with the nonlinear dynamic response of deep-sea risers subjected to parametric excitation at the top of a platform. As offshore oil and gas exploration is pushed into deep waters, difficulties encountered in deep-sea riser design may be attributed to the existence of parametric instability regarding platform heave motions. Parametric resonance in risers can cause serious damage which might bring disastrous accidents such as environment pollution, property losses and even fatalities. Therefore, the paranletric instability analysis should attract more attention during the design process of deep-sea risers. In this work, an equation of motion for a deep-sea riser is derived firstly. The motion equation is analyzed by the Floquet theory which allows the determination of both system response and stability properties. The unstable regions in which parametric resonance easily occurs can be determined. The effects of damping on parametric instability are also investigated, and the stability maps are presented. The results demonstrate that the available damping is vital in suppressing the instability regions. The suggestions for reduction of instability regions are proposed in deep-sea riser design.

Experimental research on grouser traction of deep-sea mining machine

The traction characteristics of the grouser, cutting the simulative soil of deepsea sediment, with different tooth widths, tooth heights, and ground pressures are studied with traction characteristic test apparatus. A traction-displacement model is obtained by combining the analysis of the cutting mechanism. The results show that the tractiondisplacement curves of grousers with different tooth widths, tooth heights, and ground pressures have the same changing trend, which matches the Wong traction model. Their sensitivity coefficient and shear modulus are slightly fluctuated. Therefore, the average values can be used as the traction model parameters. The maximum traction of the grouser with a two-side edge and a 10 mm tooth width increment changing with the tooth height and ground pressure can be determined according to the grousers with different tooth widths. By combining the traction model parameters, the traction-displacement curve of the grouser with a certain group values of tooth width, tooth height, and ground pressure can be predicted. Therefore, the slip of the mining machine can be prevented to improve the mining efficiency.

Predicting the sinkage of a moving tracked mining vehicle using a new rheological formulation for soft deep-sea sediment

The sinkage of a moving tracked mining vehicle is greatly af fected by the combined compression-shear rheological properties of soft deep-sea sediments. For test purposes, the best sediment simulant is prepared based on soft deep-sea sediment from a C-C poly-metallic nodule mining area in the Pacific Ocean. Compressive creep tests and shear creep tests are combined to obtain compressive and shear rheological parameters to establish a combined compressive-shear rheological constitutive model and a compression-sinkage rheological constitutive model. The combined compression-shear rheological sinkage of the tracked mining vehicle at dif ferent speeds is calculated using the Recur Dyn software with a selfprogrammed subroutine to implement the combined compression-shear rheological constitutive model. The model results are compared with shear rheological sinkage and ordinary sinkage(without consideration of rheological properties). These results show that the combined compression-shear rheological constitutive model must be taken into account when calculating the sinkage of a tracked mining vehicle. The combined compression-shear rheological sinkage decrease with vehicle speed and is the largest among the three types of sinkage. The developed subroutine in the Recur Dyn software can be used to study the performance and structural optimization of moving tracked mining vehicles.

Theoretical analysis of effect of solid phase on cavitation performance of deep-sea mining pump

In view of the present situation of low cavitation performance of deep-sea mining slurry pump, the effect of solid phase on the cavitation performance of deep-sea mining pump is analyzed theoretically. The relationship between gas and liquid phases are established by cavitation nucleon theory and mass energy equation as well as solid phase and liquid phase, and then we explored the relationship between gas phase and solid phase. The results show that the critical bubble radius and solid-phase concentration flow rate during the cavitation can be related to the liquid pressure. Eq.(19) show that the larger the solid particle concentration and the solid phase flow, the earlier the cavitation will occur, and pump anti-cavitation performance will decline.

Review of Nodule Mineral Image Segmentation Algorithms for Deep-Sea Mineral Resource Assessment

A large number of nodule minerals exist in the deep sea.Based on the factors of difficulty in shooting,high economic cost and high accuracy of resource assessment,large-scale planned commercial mining has not yet been conducted.Only experimental mining has been carried out in areas with high mineral density and obvious benefits after mineral resource assessment.As an efficient method for deep-sea mineral resource assessment,the deep towing system is equipped with a visual system for mineral resource analysis using collected images and videos,which has become a key component of resource assessment.Therefore,high accuracy in deep-sea mineral image segmentation is the primary goal of the segmentation algorithm.In this paper,the existing deep-sea nodule mineral image segmentation algorithms are studied in depth and divided into traditional and deep learning-based segmentation methods,and the advantages and disadvantages of each are compared and summarized.The deep learning methods show great advantages in deep-sea mineral image segmentation,and there is a great improvement in segmentation accuracy and efficiency compared with the traditional methods.Then,the mineral image dataset and segmentation evaluation metrics are listed.Finally,possible future research topics and improvement measures are discussed for the reference of other researchers.

Experimental Investigation on Vortex-Induced Vibration of Deep-Sea Risers of Different Excitation Water Depths

The vortex-induced vibration test of the deep-sea riser was carried out with different excitation water depths in the wave-current combined water flume.By dimensionally changing the multi-stage water depth and hydrodynamic parameters such as outflow velocity at various water depths,the dynamic response parameters such as dominant frequency,dimensionless displacement and vibration trajectory evolution process of the riser under different excitation water depths were explored to reveal the sensitive characteristics of the dynamic response of vortexinduced vibration of the risers under different excitation water depths.The results show that different excitation water depths will change the additional mass of the riser and the fluid damping and other parameters,which will affect the spatial correlation and stability of the vortex shedding behind the riser.In the lock-in region,the distribution range of the characteristic frequency becomes narrow and centered on the lock-in frequency.The increase of the excitation water depth gradually advances the starting point of the lock-in region of the riser,and at the same time promotes the excitation of the higher-order vibration frequency of the riser structure.Within the dimensionless excitation water depth,the dominant frequency and dimensionless displacement are highly insensitive to the excitation water depth at high flow velocity.The change of the excitation water depth will interfere with the correlation of the non-linear coupling of the riser.The“8-shaped”gradually becomes irregular,and the vibration trajectories of the riser show“O-shape”,“X-shape”and“Crescent-shape”.

Influence on the Solid−Liquid Two-Phase Flow from Cross-Section Area of Slurry Pumps for Deep-Sea Mining

To explore the mechanism of solid-liquid two-phase flow in deep-sea mining pumps,this paper investigates the influences of the impeller cross-section area on the multi-phase flow in the slurry pump.Experimental and numerical results are presented for two-phase flow in four impellers with different cross-section areas.They show that the degree of vortex strength and the passing capacity of particles increase as the cross-section area of the impeller.In addition,the correlations between the two-phase flow and cross-section area have been revealed by a mathematical model taking the force of the flow field into account.The simulation results confirm the theoretical analysis,while the experimental pump performances validate the numerical calculation.The influence of the cross-section area on two-phase flow and pump performance could provide theoretical support for the design of high-performance deep-sea mining slurry pumps.

基于尾流振子模型的柔性悬挂立管涡激振动分析

为了分析深海采矿柔性立管涡激振动响应特性,提出了一种高效的针对特殊边界的处理方法.基于欧拉梁模型和尾流振子模型,结合有限差分方法,系统研究不同边界条件、中间仓质量和海流剪切参数对深海采矿立管涡激振动的影响规律.结果表明:悬挂立管底部会产生较大位移,与传统两端铰接立管相比,相同激励下悬挂立管会激发出更高阶的振动模态,从原本5阶模态升至6阶;随着中间仓质量增加,立管振动的主导模态会随之降低,在同一模态下,悬挂立管底部位移逐渐减小,从0.460降至0.405,当模态转换时,底部位移均方根会迅速增大,由0.405升至0.413;底部位移随着均匀流速的增加呈现出波动趋势,在一定流速范围内,位移随流速线性变化;随着剪切参数增大,在同一模态下,立管底部的位移逐渐减小,当模态转换时,底部位移会增加.

横向振动立管上升流中球形单颗粒运动特征

深海采矿过程中,输送矿石颗粒的立管在复杂海洋环境作用下会产生运动响应,这会对管道中矿石颗粒的运动行为产生重要影响,从而影响矿石提升效率,甚至可能危及整个采矿系统的安全.结合颗粒运动方程和软球碰撞模型,对横向振动立管中的球形单颗粒运动特征进行研究,主要分析了立管振动参数、颗粒与流体密度比以及颗粒与立管直径比对立管中单颗粒运动的影响.研究表明,随振动频率和幅度、颗粒与流体密度比以及颗粒与立管直径比的增加,颗粒垂向平均速度减小.颗粒与管壁之间无碰撞发生时,颗粒与立管之间横向相对速度幅值、颗粒运动与立管之间横向速度的相位差以及颗粒垂向速度波动幅值,与立管振动的频率和振幅、颗粒与流体密度比以及颗粒与立管直径比呈正相关.然而,当颗粒与立管之间有碰撞发生时,颗粒与立管间的横向速度的相位差减小,而颗粒垂向速度波动幅值显著增大.另外,随着密度比和直径比的增大,颗粒与管壁之间更容易发生碰撞,而碰撞会减弱密度比和直径比对颗粒横向速度和垂向速度的影响.

深海采矿立管在波流载荷下的弯矩响应分析

采矿立管是深海采矿系统的重要组成部分,立管的弯矩分析是确保立管正常使用的重要指标。立管所处海洋环境复杂,且立管底部的自由边界条件使得立管弯矩特性难以分析。本文基于波浪理论,使用Abaqus有限元软件建立海洋采矿立管的模型,运用Abaqus中的AQUA海洋工程模块,考虑立管在轴向力、自重、浮力、波浪载荷、海流载荷及模拟海上平台水平和升沉运动共同作用下,对采矿立管进行弯矩分析,计算了提升泵不同安装位置、不同中继仓重量变化对弯矩的影响,结果表明:提升泵会增大安装位置的弯矩幅度,且安装在不同位置对立管弯矩会产生叠加影响;中继仓重量的增加提高了立管整体稳定性,但会使提升泵处弯矩波动产生向中部延伸的不利影响。

基于数据融合及残差卷积自编码器的结构损伤识别方法

深海混输立管作业期间持续遭受外部风浪流耦合荷载及内部矿液两相流体磨蚀作用,长期作用下结构损伤逐渐积累。立管结构呈高长细比、柔性状态,传统结构损伤识别过程中存在模态参数识别困难、单测点响应损伤敏感度低等诸多问题。针对上述问题,该研究提出了基于数据融合及一维残差卷积自编码器(one dimension residual convolution autoencoder, 1D-RCAE)的深海混输立管结构损伤识别方法,以结构损伤敏感的应变动态响应为输入,使用主成分分析(principal component analysis, PCA)进行多测点应变响应特征融合,进一步利用1D-RCAE自动提取损伤敏感特征,以结构损伤前后敏感特征间的马氏距离构建结构损伤判定指标,实现混输立管结构健康状态监测。通过500 m深海混输立管结构数值模拟和立管物理缩尺模型试验对该研究提出的方法进行验证,结果表明,有限测量信息下能够有效实现深海混输立管结构损伤识别,其中数值模拟验证损伤识别准确率高于99%,物理模型验证损伤识别准确率高于98%。同时探究了噪声污染、海洋环境因素变化对该研究提出方法损伤识别性能的影响规律。

垂直扬矿管道堵塞条件下的水力特性

基于试验研究,探讨了不同颗粒粒径(d)、堵管高度(H)、流体平均流速(V)条件下粗颗粒在垂直扬矿管道中堵管后再起动的临界条件。研究结果表明:(a)d和H是影响单位长度压差(ΔP)与V关系的2个重要参数。(b)当ΔP与V呈线性关系时,垂直管道堵管后颗粒将无法实现再起动;反之,如若二者呈非线性关系,则颗粒可实现再起动。(c)基于试验结果提出的颗粒再起动时的临界流速、临界单位长度压差计算公式符合精度要求。

多绳缠绕式超深井提升机提升段钢丝绳动态张力检测方案研究

针对多绳缠绕式超深矿井提升机在运行中存在提升段钢丝绳动态张力测量难且动荷载对安全生产影响较大的问题,在充分考虑动态工况下,结合提升系统受力情况,建立数学模型和方程,提出了准确实用的检测方案,从而实现提升段钢丝绳动态张力的可靠检测,保障超深矿井提升机的安全运行。

深海矿物资源开发系统关键力学问题及技术挑战

海底矿产资源丰富,但环境复杂恶劣,对深海矿物资源开发系统构成极大的危害。本文简述了国内外深海矿物资源开采系统的发展进程及几种典型的深海资源开采系统,基于复杂多变的海况,提出了深海矿物资源开采系统所涉及到的关键力学问题及技术挑战,从矿物资源开采系统的总体设计及集成控制、采矿车采集动态性能控制、立管输送系统动态特性、环境监测与评价等主要关键部分概括了目前采矿系统所面临的技术挑战。