Researches on Deep Ocean Mining Robots: Status and Development

With the development of shallow surface mineral resources in metal mines, it is gradually turning to the stage of deep mining. According to the current mining depth and the average annual depth, during the period of “14th Five‐Year Plan,” one‐third of the underground metal mines will reach or exceed the mining depth of 1,000 m, with the deepest being 2,000 m. In the stage of deep mining, mines will face the conditions of high stress, high temperature, high well depth, and strong mining disturbance, which will greatly increase the difficulty of large‐scale deep mining. Among them, the high ground stress environment is the principal problem of many technical problems in deep mining. The selection of mining method has become a prerequisite for solving the problem of efficient and safe mining of deep deposits. In this paper, the vague set theory was introduced into the selection of mining methods and a vague set model for deep unloading mining schemes was established. Taking the Jinchuan No. 2 mining area as the engineering background, four unloading schemes for deep mining were proposed, and the Vague set model was used for optimization. It is concluded that the mining approach with large‐section unloading is the optimal unloading mining plan. The application shows that it has the advantages of high unloading efficiency, large production capacity, and low loss index. It has been fully promoted in the deep mining of the mining area. It is feasible and effective to use the vague set theory in the selection of deep unloading mining schemes, which provides a proper approach in the selection of deep unloading mining schemes.

Deep mining has become an inevitable trend of mining development. Previously conducted studies have established that reasonable stope structure parameters are the premise to ensure the safe and efficient production of deep mines. In order to ensure the safety of deep mining, in this paper, we systematically review the existing stope structure parameter design methods, and then put forward a deep stope structure design method based on the stability of mining rock mass. Based on rock mass quality classification, this method uses a critical span graph and an improved stability graph, and fully considers the influence of joint occurrence and mining stress on the stability of surrounding rock, to design the stope structural parameters. Taking into consideration the deterioration of the quality of deep rock mass, we collect mining data at home and abroad, improve the stability graph, and make it suitable for the design of stope structural parameters with different mining methods. The design process of stope structural parameters is expounded through field engineering cases, and it has specific guiding significance for the design of stope structural parameters in deep metal mines.

The mining of underground coal resources often results in extensive damage to the ground surface, particularly in China, which has a large amount of coal resources. However, the laws of surface damage caused by the mining of deep and shallow underground coal resources are relatively different. This study analyzes the difference in surface damage induced by deep and shallow mining and its mechanism by field measurement and similar material simulation experiments. Surface damage is mainly manifested in the form of cracks, which can be categorized as permanent and dynamic cracks. Permanent cracks occur above the mining boundary of shallow and deep coal mines. Dynamic cracks (including dynamic stretching cracks and stepped cracks) only appear above the goaf in shallow mining. This disparity is due to the fact that strata movement in deep mining occurs in a “three zones” mode, with the failure height of strata increasing with the mining degree in an “S” shape. However, rock strata movement in shallow mining follows a “two zones” mode, with the failure height of rock strata increasing exponentially with the mining degree. Thus, the rock strata are prone to slide and become unstable in the form of benched rock beams, producing dynamic cracks, such as stepped cracks on the surface. This research improves the existing mining subsidence theory and provides technical support for relevant mines to take targeted treatment measures.

Purpose. Development of an adequate model of steel arch support for underground workings of deep coal mines to assess its stress-strain state. Methodology. The study of the deformation of steel arch supports in main workings of deep coal mines, comparing them with the results of analytical studies, considering the peculiarities of the time-dependent geomechanical processes in the rock mass near the face, and development a new mechanical model of the deformation of steel arch support during its loading based on this. The research employed methods of structural mechanics, field studies, and statistical processing of field measurement results. Results. Considering the development of geomechanical processes during the advance of the face, a new two-stage deformation model of steel arch support has been proposed, which operates in the first stage under a regime of specified deformations due to the movement of the contour of the workings, and in the second stage under a regime of specified loading after the loss of stability of the rock at the bottom, which will allow for a reasoned approach to the design of support, justification of its rational form, and ensuring the stability of underground workings in deep mines and quarries. Scientific novelty. Based on the patterns of deformation of steel support in capital workings, a new two-stage deformation model of steel arch support for capital underground workings in coal mines and quarries has been proposed, which corresponds to the conditions of its operation in real conditions. By analyzing the stress-strain state of the arch support, its possible forms have been justified, which have reduced material consumption and are adapted to specific mining and geological conditions. Practical significance. The new model of deformation of steel arch support in coal mines will allow for a reduction in the consumption of steel rolled special profiles used for support production, which is scarce under conditions where the main producers of special profiles – metallurgical plants named after Illich and Azovstal, both located in temporarily occupied Mariupol – have been destroyed. This will also reduce the cost of the extracted mineral resources and increase production efficiency.

Transparency in the field of deep sea mining: Filtering the murky waters

Effect of different ice contents on heat transfer and mechanical properties of concrete

Heat damage caused by deep mining is the inevitable trend in coal mine development. HEMS cooling system is a process system for high-temperature heat damage controlling in deep coal mine, in which cool energy in mine water extracted to reduce work face’s ambient temperature, to achieve heat damage controlling. We analyze the energy consumption of every subsystem during operation of the HEMS system, which could provide a theoretical basis and technical guidance on more efficiently running of cooling system deep in the future.

A typical and may be the most prospective deep ocean mining system is an integration of a mining ship system, a hoist pipeline system and a self-propelled seafloor miner system. According to this representative system configuration, China has designed and developed a deep ocean mining pilot system. In order to evaluate and improve the design of the pilot system, and further to provide technical references for the practical system operation, dynamic simulation models of the subsystems and the total integrated system are developed. For the seafloor miner, a multi-body model with the scale of 1:1 to the actual size of the pilot miner is built, which can be used effectively to perform detailed design, analysis and optimization of the miner system. Meanwhile, to make the integration of the total mining system possible, a simplified 3D single-body model with 6 DOF of the miner is also developed, which is capable of real-time simulation and can be easily integrated with other subsystems. For the pipeline system including the rigid lifting pipe, submerged pump, buffer storage and flexible hose, finite element method (FEM) and discrete element method (DEM) are all proposed and developed. With the FEM model, the towing mining operation process, as well as the launching and retrieval process, can be analyzed. Whereas, the DEM model is preferred to perform the dynamic analysis of the total integrated mining system due to its relative high computation efficiency compared with that of the FEM model. To realize the dynamic analysis of the total integrated mining system with relative high efficiency and accuracy, the single body model of the miner and the DEM model of the pipeline are chosen to be integrated to form the total system and perform dynamic analysis, which in a way can provide specific guidance and suggestions for the practical deep ocean mining system analysis, operation and control. For further researches, more attention will be focused on the analysis of the launching and retrieval operation process of the total mining system, including the water entry of the miner, the launching process of the pipeline system and the final seafloor-touchdown of the miner.

The end state of an autonomous system in South Africa's deep mines is a “fait accompli”. The current unacceptable safety records, and the increasing dangers as the mines get deeper, necessitate the removal of miners from the dangerous stope areas. Robotics seems an obvious solution. An autonomous robotic system to inspect the mine ceiling (hanging wall) is being developed at the Center for Mining Innovation as an initial robotic application for South African deep gold mines. A number of the key technologies needed to enable this are discussed. The localization system, the underground alternative to the GPS, is perhaps the single biggest hurdle needed in enabling underground robotics. A low cost, disposable solution for the small area gold stope (30m × 3m) is presented. Machine sensing of both the environment and of humans is critical in a shared working environment. Here we discuss alternatives to the current sensors used above ground for machine perception. In the deep gold mines the geothermal heat result in hot walls and thermal imaging becomes an option for structural imaging. The combination of temperature with a 3D data enables the determination of a risk measure, indicating potential danger areas. Potential methods of representing the risk data for the miner to interpret are discussed. Finally, the thermal camera in conjunction with a distance sensor is used to identify and track pedestrians in order to predict potential collisions.

The paper deals with model tests as a means for research and development of deep sea mining vessels. Important data can also be collected for operation manuals concerned with precise specification of operations of ocean surface units. The paper reviews deep ocean mining vessels and operations and outlines the aspects which can be successfully dealt with in model tests in conventional wave basins. A range of special techniques are used to obtain the necessary information for the main set-up of the mining vessel in operation and the ore carrier in approach, attach, load, detach, and depart phases of the combined operations. It is discussed how operational conditions and survival conditions can be studied for the above objectives. The model test set-up for the purpose is complex since the many quantities and phenomena covered do not scale similarly. It is shown how servo-assisted free-model tests is the answer to the problems encountered in terms of model testing. The necessary servo units are discussed and dealt with in the appendices. Finally, the paper outlines a test programme and the ranges of test parameters and variables. INTRODUCTION Deep sea mining is a very young technology and very expensive to develop. Basic tests and pilot plants have been operated for some years to investigate possibilities and prepare the full-scale process when the law of the sea legislation and the mineral market conditions are right. The cost of an ocean mining installation for manganese nodules is about 700 million US $ and seems, under certain conditions of high nodule abundance and relatively easy recovery, to be economically feasible with a 20 years' operation in the mining sites. The nodule density of about 9 kg/m2 over a high priority area of 6,000,000 km2, will yield about 40 billion tons of dry nodules for recovery. The operation cost of such a mining system can be estimated to the order of 75 million $ per year exclusive of processing cost which might amount to 125 million per year, and exclusive of capital cost. The direct mining cost is thus 250,000 $ per day covering all operations at sea. Any attempt to improve efficiency and service operation quality or any attempt to prolong the possibility to operate in heavier weather is worth-while. Model tests are a highly qualified means of developing ocean structures, and many aspects of ocean mining can be solved in model tests. The vessels' motions and behaviour under environmental loads, steering and manoeuvring properties at the low speed of advance, carrying a 6 to 8 km long marine riser under the ship bottom, can be measured and analysed for design, development, and preparation of operation manuals. Films and video tapes can be prepared for instructions, marketing, and training purposes. Structural loads for design purposes concerned with mutual operation of the mining vessel and the ore carrier can be studied. Transfer of the recovered ore in dry or slurry form can be dealt with.

In recent years, there have been a number of developments in deep mining research with respect to safety mechanisms and disaster prevention and control. However, it will be difficult to fully resolve the challenges associated with disaster prevention and reduction based on current theories and technologies, and as yet no sound deep mining research approach regarding cataclysm and its control has been established. This paper reviews the literature and discusses problematic research areas associated with deep mining disasters, including in-situ stress measurement and its distribution law, deep rock mechanics and the coupling damage mechanism, dynamic disaster mechanism and prediction, and the water inrush mechanism and early warning, as well as the surrounding rock deformation mechanism and control technologies. This paper analyzes the deficiencies in existing research and identifies key problems that must be solved in deep-mining-induced disasters. Lastly, this paper indicates future prospects in the study of ultra-deep mining disasters.

The particulars and procedures of deep ocean mining are presented. Emphasis is placed upon design uncertainties and their influence on operational efficiency. Requirements which have evolved as a consequence are identified and reviewed. Particular focus is directed towards navigation, communications, data transfer, accurate real-time weather monitoring, and prediction of sea and atmospheric conditions. It is concluded that deep ocean mining will be, to a large extent, dependent upon the transfer of operational information, its availability, accuracy, and reliability.

Heat stress in deep hot mines is a factor that often determines the possibility of technical mining of natural resources. One of the solutions enabling miners to work in such mines is air cooling. Cooling systems vary, and their selection depends on the type of mine and the mining methods used. Limited air cooling capabilities exist in electric-powered coal mines. The main solution for air cooling is based on movable spot air coolers. Such systems commonly use surface or underground refrigeration plants. An underground refrigeration plant (URP) equipped with compressor chillers does not achieve more than 2.5–3.0 MW of cooling capacity due to the limited heat rejection capacity of return air streams in a typical coal mine. The method discussed in this paper, using mine water to discharge waste heat from the underground refrigeration plant, provides a measurable benefit for optimizing the mine air cooling system. The main purpose of this research is to study the feasibility and effect of water diversion from the actual mine drainage system to the underground refrigeration plant. The water drainage system in an underground mine is called the dewatering system of the mine. The heated water in the condensers of the chillers is directed back to the mine’s central dewatering system. The recovery from water discharged to the surface contributes to optimising energy consumption for a mine air cooling and the sustainable discharge of wastewater. In addition, using the total water flow from the mine dewatering system to reject heat in compressor chillers, compared with the traditional solution, can improve the cooling capacity of URP. These findings may provide beneficial guidance for practical applications in deep hot mines with small natural water inflow.

In China, mine curtain grouting has become an important technology to ensure the safe and efficient mining of deep mineral resources and protect regional groundwater resources after more than 60 years of development and improvement. This review paper summarizes and analyzes four aspects of the current situation of curtain grouting technology in deep underground mines: curtain construction conditions, theoretical design and effects, drilling structures, and grouting materials’ research and development. In addition, several main problems of curtain grouting technology in deep underground mines are analyzed: planning and construction lag behind; the theory of mine curtain grouting is not mature enough; the investigation into the mechanism of consolidation and deterioration of grout slurry under long-term high pressure is insufficient; there is a lack of research on the long-term effectiveness of monitoring and evaluation, so precise drilling control technology needs further breakthroughs. In addition, the development directions of this technology are put forward from three aspects: precise directional drilling technology; the consolidation mechanism and durability of slurry under multi-field coupling conditions; and long-term dynamic monitoring, evaluation, and early warning for grouting curtain effectiveness. In the future, mine curtain grouting will become an important mine geological guarantee technology for safety, efficiency, accurate, sustainability, and green mining of the Earth’s deep resources.

The urbanization, the rising of the population, the development of technology along with the elevating level of our everyday lives increase the need for mineral resources, which have multiple appliances. Until now, such deposits were found in terrestrial sites, which however, will soon expire. Therefore, the deep sea mining could be the solution to cover humanity’s needs. However, the limited knowledge on deep sea ecosystems and restricted environmental baseline information currently available are prohibiting to move towards the mining of deep-sea resources, as serious harm can be caused to the environment. As the sea has no boundaries, mining activities can have impacts in various places and users of the marine area. To date, only test mining and exploration activities have taken place worldwide, without however moving to the next phase, which is the exploitation of the available deposits. The Authority which regulates the deep-sea area (meaning the marine area beyond national jurisdiction) is the International Seabed Authority which, via a set of regulations and various recommendations and guidelines, controls the mining activities in the deep sea. The International Seabed Authority supports that the activities should take place basis a precautionary approach, adaptive management and to conduct Environmental Impact Assessment and Environmental Management Plans, as the goal is to proceed with mining in the future, but in a sustainable manner, to protect the deep sea environment for our sake and the generations to come. Through studying the case of Clarion- Clipperton Fracture Zone, one of the areas with growing interest for its mining due to high concentration in polymetallic nodules, it has become apparent that the scientific knowledge is still limited, and it is the needful factor to address environmental thresholds in order to proceed with the mining phase. By raising scientific knowledge, and understanding the ecosystems and their connectivity, the environmental thresholds can be managed and understood, in order to avoid irreversible environmental harm.