Search

In order to solve the problems of ignoring multi-dimensional load characteristics, cumbersome modeling process and long design cycle in the design process of hydraulic support in steeply dipping angle coal seam, combined with the load characteristics of hydraulic support in large dip angle pseudo-inclined working face, the design system of large dip angle hydraulic support is developed. Based on the comprehensive research methods of motion simulation, strength test and physical experiment, taking the design of ZY5000/15.5/38 hydraulic support for steeply dipping angle coal seam as an example, the mechanical model is established according to the multi-dimensional stress characteristics of hydraulic support in large dip angle pseudo-inclined stope. The spatial load characteristics of large dip angle hydraulic support are analyzed, and the mechanical linear matrix of top beam and shield beam of hydraulic support in pseudo-inclined working face is established. The design system of hydraulic support is built by using VB.NET as the development language combined with linear matrix and SOLIDWORKS secondary development modeling software, and a good human-computer interaction user interface is developed. The research and analysis show that the trajectory range of the front end of the top beam of the model hydraulic support generated by the system is about 48 mm, and the trajectory curve of the front end of the top beam of the support satisfies the characteristics of double torsion line. The maximum stress value of the model support is 146.7 MPa, which is far less than the equivalent stress value of the material yield, and the maximum deformation displacement is not more than 0.531 mm. The working resistance of the physical model hydraulic support with a similarity ratio of 1:5 is about 38 kN. The loading characteristics of the top beam and the shield beam of the support are tested under different conditions. The mechanical data of the model support in the experiment are basically consistent with the mechanical data generated by the system, and the experiment meets the motion requirements and bearing characteristics of the support in the stages of initial support, resistance increase, constant resistance and pressure relief. The research results reflect the good adaptability of the model hydraulic support under the design system, which has certain scientific and practical significance for enriching the design theory of hydraulic support in steeply dipping angle coal seam and guiding the design and production of hydraulic support.

The hydraulic support is the core of the stability of the ‘surrounding rock and equipm ent’ system in the pitching oblique working face of steeply dipping coal seam. The existing hydraulic support structure can not meet the requirements of spatial stability of pitching oblique mining, which seriously affects the safe and efficient mining of working face under such conditions. Taking the pitching oblique working face of steeply dipping coal seam as the research background, the comprehensive research methods of engineering analogy, structural kinematics analysis and numerical simulation are used to analyze the stability characteristics of ‘support-surrounding rock’ in the pitching oblique working face of steeply dipping coal seam. Based on ZY7000/22/45 hydraulic support, a new parallelogram hydraulic support is invented, the structural rationality design is carried out, and the kinematic response characteristics of key components are analyzed.The research shows that the non-uniform filling of the caving gangue and the crushing, pressing and pushing effect of the gangue on the support are the key factors affecting the stability of the support. The parallelogram top beam and the base are more suitable for the pitching oblique working face. The arrangement of the top beam, base and column of the parallelogram support is parallelogram. The special-shaped shield beam, the rear connecting rod, the oil cylinder connecting rod and the base constitute a flexible four-link structure. The column of the parallelogram support is the main bearing structure, and the cylinder connecting rod is the main motion mechanism. The main influencing factors of its motion characteristics are the distance between the upper and lower column sockets and the distance between the front and rear connecting rods and the hinged position of the shield beam. The shield beam and the rear connecting rod are the key to the position and posture control of the support, and there is no double torsion line during the movement of the support. The research results provide a type selection for the support of this kind of working face, which ensures the safe production of this kind of coal seam to a certain extent.

The structure and stress environment of the surrounding rock at the longwall mining area in the steeply dipping coal seam are alienated, and the composition factors and disaster modes of the ”support and surrounding rock” system in the working face are affected. This leads to some frequent safety accidents in the working face, low coal extraction rate, and high roadway excavation rate. This paper analyzes the mining mechanics behavior of surrounding rock of in the steeply dipping coal seam and proposes a technological concept of partial backfill non-pillar mining in the longwall faces of steeply dipping coal seam. During the process of advancing the working face, partial backfill is carried out along the inclined direction in the lower part of the goaf. The filling body not only forms a gob-side roadway with the support effect of the roadway side, but also eliminates the protection coal pillar, achieving a non-pillar mining. At the same time, the length of the filling and compaction area at the lower dip of the working face is increased, enhancing the stability of the ”support and surrounding rock” system of the working face. Based on the characteristics of the longwall mining area in the steeply dipping coal seam, the partial backfill process of the steeply dipping coal seam paste was optimized and determined. And the partial backfill recovery system and mining and filling process in the steeply dipping coal seam were designed. By using a combination of theoretical analysis, simulation experiments, and numerical calculations, the regulatory mechanism of partial backfill on the mechanical behavior of surrounding rock at the longwall mining area in the steeply dipping coal seam was analyzed. The results show that the filling body affects the deformation and failure of the main roof rock beam, as well as the bearing characteristics of the coal and rock mass on the lower side of the mining area. The deformation of the main roof and the roof of the head entry, as well as the constraints on the coal and rock mass on the lower side of the head entry, all decrease with the increase of filling length. In order to prevent the hanging roof disaster in the unfilled area of the goaf, the filling length should not exceed 1/3 of the working face length. The partial backfill body restricts the fracture of the roof in the lower area of the working face, reduces the formation layer of the critical zone of the overlying rock, forms a stable roadway, and reduces the deformation of the surrounding rock gob-side roadway retained. At the same time, the length of the filling area at the lower part of the working face increases, and the length of the unstable area of the middle and upper surrounding rock structures decreases, improving the stability of the ”support and surrounding rock” system. The filling body changes the stress transmission path of the surrounding rock in the mining area, bearing part of the overlying rock load. The side abutment pressure on the lower side of the working face and the front advanced pressure both decrease with the increase of filling length, and the front support pressure in the lower filling area of the working face has the greatest decrease. The stress state of the gob-side roadway and the working face is improved. Technology of partial backfill non-pillar mining in the longwall faces of steeply dipping coal seam has the advantages of effectively improving resource recovery rate, reducing the roadway drivage ratio, alleviating the tension of mining and replacement, and strengthening the stability of the ”support and surrounding rock” system in the working face. It is of great scientific significance for guiding the green, safe, and efficient mining in the steeply dipping coal seam.

The steeply dipping coal seam is one of the main forms of coal storage in China. It is widely and regionally distributed. According to incomplete statistics, twenty-six provinces, autonomous regions and municipalities directly under the central government are involved in the mining of such coal seams, with abundant reserves, large production and high production concentration in the central and western regions. It shows diversity and complexity in terms of the conditions of existence, with different regions having different coal formation periods and different tectonic control processes, forming diverse and complex mining conditions and giving rise to different mining technology requirements. The mining of steeply dipping coal seam is technically difficult. The asymmetry of the movement and damage of the peripheral rock in the mining area affected by the inclination angle of the coal seam is obvious, and the difficulty of the stability control of the support system and equipment, the matching and coordination of the “three machines”, the layout and support of the mining roadway, and the safety guarantee of the “human-machine” environment at the working face has increased significantly, which seriously restricts the safe and efficient mining of the mine. This has seriously restricted the improvement of safe and efficient mining. The regional economic demand for the mining of steeply dipping coal seam is strong. This kind of coal seams and the production of more concentrated areas are mostly seen in the coal industry-based resource cities, the economic structure is relatively single, the safe and efficient development and utilization of coal resources for the regional energy supply, people’s livelihood, economic stability has the role of the bottom of the pocket, the demand is urgent. For a long time, mining technologies for the steeply dipping coal seam changes focus on solving the “difficult” and “need” contradiction. In the coal mining methods and techniques, strata control theory and technology, complete sets of equipment development and application of the three aspects of continuous improvement, innovation, development, to achieve the transformation from non-mechanized to fully-mechanized mining, the level of safety and production efficiency has increased dramatically, the personnel labor intensity has decreased dramatically, and the operating environment has improved significantly. In the mid-1990s, Lvshuidong Coal Mine of Sichuan Coal Industry Group Limited Liability Company successfully realized longwall fully-mechanized mining in steeply dipping coal seam with medium mining height for the first time, breaking through the "forbidden zone" in this filed. Under this demonstration, the three pioneering engineering practices of longwall fully-mechanical mining of steeply dipping coal seam with thick mining height, steeply dipping coal seam with large mining height, and longwall fully-mechanical mining of steeply dipping coal seam with thin mining height in pseudo-inclination have been successful successively, which innovated the non-linear limiting arrangement of the working face and the way of adjusting the slanting, established a multi-dimensional interactive control mode of the system stability of the “bracket-surrounding rock”, and researched and developed the “support and stability and heavy weight, high-strength and light-weight, safe and reliable, and matching synergistic” complete set of equipment of the working face, which has achieved good results, and the scope of application of the comprehensive mechanized mining technology has further been widened. At the same time, there are still many key scientific problems and technical bottlenecks that need to be broken through in the mining of steeply dipping coal seams, resulting in a large gap between the intelligence level and that of the flat/gently inclined coal seams. Research on the mining dynamics of coal and rock bodies in inclined bedded coal beds, revealing their control mechanisms on the disaster of the surrounding rocks in the mining field, and realizing quantitative characterization need to be further strengthened. It is necessary to further clarify the multi-dimensional dynamic process and law between the system of “rock-bearing structure - mining equipment group”, improve the theoretical and technological basis of “multi-dimensional dynamic multi-objective synergistic control of equipment and surrounding rock”, and realize the transformation and application of the technology. On the basis of breakthroughs in scientific issues, we will carry out systematic technological innovation and research and development of coal mining methods, mining techniques, rock formation control, and complete sets of equipment, so as to crack the bottleneck of the constraints on the double enhancement of “safety and efficiency” in the mining of steeply dipping coal seams, and make the upper limit of the inclination of the steeply dipping coal seams for comprehensive mechanized mining extend upward under the prerequisite of reliable technological safeguards, so as to lay the foundation for the realization of automated and intelligent mining.

Coal wall of large mining height face in steeply dipping coal seam has large free height, wide free movement space and poor self-stabilization balance, coal wall is not an isolated body in the face, it can form a load-bearing structure with the surrounding rock, supports and other mediators, and the mining behavior is closely linked. The dip angle effect can easily promote the dissimilation of the coal wall bearing environment, complicate its response behavior, increase the difficulty of coal wall and surrounding rock stability control, and restrict the safe and efficient production of the face. In order to solve the problem of coal wall stability control of large mining height face in steeply dipping coal seam, theoretical analysis and numerical calculation are comprehensively used for research. The stress in the plastic zone of large mining height face in steeply dipping coal seam increases exponentially, there is an asymmetric arch residual stress influence zone in the vicinity of the coal wall, the plastic zone breadth is dissimilated in different regions, and the width from large to small is the upper, middle and lower part, and the distribution pattern is in the shape of stepped arch, coal in the plastic zone bears repeated pressure, and will be enhanced with the expansion of plastic zone. As the mining height increases, the residual abutment pressure near the coal wall decreases, the compressive strength, displacement value and disturbed range of the coal in front of the coal wall will increase. The stress and transport of the coal wall under the dip angle effect develop in a zonal manner, in which the stress distribution is lower> upper> middle, while for the displacement is middle> upper> lower. In addition, the working face inclination under the oblique angle will lead to the transformation of the coal wall instability mode, when the oblique angle is large, the dip angle of face is small, the compression component of abutment pressure is enhanced, and the external convex spalling mainly occurs. On the contrary, it’s the sliding instability under the coupling of mining stress and self weight. The comprehensive analysis shows that the coal wall mining behavior is regionally heterogeneous under the coupling effect of dip angle and mining height, and because the stress unloading and migration in the middle and upper part of the face are larger, therefore the two regions should be the key prevention and control areas for coal wall instability of large mining height face in steeply dipping panel.

Steeply dipping seam is still internationally recognized as a complex and difficult coal seam. There are many and extensive coal seams in China with excellent coal quality. In recent ten years, the advanced longwall fully-mechanized mining technology of steeply dipping seam has developed rapidly, the working environment has been improved, the labor intensity has been reduced, and the safety level has been improved. However, there have been some urgent problems to be solved, such as low output and poor efficiency. The economic advantages and investment benefits of fully-mechanized mining technology cannot be fully exerted, which restricts the efficient and sustainable development of fully-mechanized mining in steeply dipping seam. Based on years of systematic research and engineering practice, the comprehensive analysis shows that the production efficiency of fully-mechanized mining in steeply dipping seam is mainly restricted by six factors, such as geology, equipment, technology, personnel, management and others, and the weight of each factor is determined. According to the weight of each influence factor, we should take targeted measures such as Precise detection, precise maintenance, precise operation, precise management, precise training and precise supplement In particular, we should pay more attention to the development direction of mining automation and intelligence, and take it as the core accurate countermeasure for promoting production and efficiency of fully-mechanized mining in steeply dipping seam, so as to fundamentally change the passive situation of large number of people and low production efficiency of fully-mechanized mining in steeply dipping seam. The goal of safety, high yield and reducing human efficiency in long wall comprehensive mining in steeply dipping seam is realized.

In order to solve the problem of solder balls being prone to oxidation during long-term storage and transportation, a novel water-based polymer surface treatment agent for solder balls was prepared and researched, with solder balls of Sn3.0Ag0.5Cu serving as the research object. The surface treatment agent was formulated with benzotriazole and polyvinyl alcohol 4000 as film-forming agents, using ascorbic acid as an antioxidant, and incorporating a small amount of alkaline complexing agents and surfactants. The solder balls, processed by this surface treatment agent, were characterized through an oxidation resistance test, shear strength test, cavity test, coating condition test and Raman spectroscopy. Results showed that after treatment with this surface agent, the shear strength of the solder joint of the solder ball increased by 48%; the cavity rate of the solder joint of the solder ball was less than 4%, meeting the industry requirements(less than 15%). These results indicated that the solder balls treated with this surface treatment agent formed a dense anti-oxidation film on their surface, improving the oxidation resistance of the solder balls.

In fourth-generation reactors, fast reactors characterized by high average neutron flux, proliferating fission nuclear fuel, and transmutation of long-decay actinides have become the primary research focus in China. NECP-SARAX is an advanced reactor neutron analysis and calculation system independently developed by the Nuclear Engineering Computational Physics Laboratory of Xi'an Jiaotong University. Based on the features and functions of NECP-SARAX, Xi'an Jiaotong University has developed a customized LoongSARAX system specifically for core physical engineering design and safety evaluation of liquid metal cooled fast reactors. LoongSARAX includes cross-section generation module TULIP and core steady-state analysis module LAVENDER. TULIP is used for the calculation of uniform assemblies, and for addressing one-dimensional plate and cylinder problems. LAVENDER is used for the 3-D core calculation for advanced reactor neutron analysis systems. After obtaining the few-group cross sections for each assembly, LAVENDER employs multi-group neutron transport methods to calculate the core's primary parameters. LAVENDER calculates a variety of parameters for liquid metal cooled fast reactor cores, including criticality, power distribution, reactivity, burnup, etc. In the course of software development, discrepancies between the results obtained through software calculations and actual results are inevitable. If LoongSARAX is to be applied to engineering practice, it is indispensable to ensure its normative and systematic verification and validation (V&V). Relevant international data on the physical calculation benchmark of liquid metal cooled fast reactor were collected and collated in this paper, with a focus on the V&V of LoongSARAX. On this basis, the V&V matrix for the LoongSARAX program was established. In order to improve the accuracy of verification, the whole program was divided into different modules for module verification, subsystem verification and system verification respectively. LoongSARAX was referred to as the system, with TULIP and LAVENDER being its subsystems. The V&V process begins with modules in TULIP and LAVENDER, followed by the system as a whole. The V&V of LoongSARAX covers fast reactors with sodium and lead coolants, such as JOYO, ZPPR17A, FFTF, BFS, etc. By comparing the calculation results of LoongSARAX with the experimental measurement results or MCNP results in the benchmark reports, it can be clearly concluded that LoongSARAX has high calculation accuracy and reliability in the field of liquid metal cooled fast reactor. In summary, LoongSARAX, a computing system developed by Xi'an Jiaotong University for liquid metal cooled fast reactors, demonstrates excellent computing capabilities after undergoing rigorous and systematic V&V. This will provide strong support for the core physical engineering design and safety evaluation of liquid metal cooled fast reactors, and the application of LoongSARAX will also provide valuable experience for the development and promotion of fast reactors in the future.