Abstract Coal and rock mass bear loads together in underground engineering such as coal mining and roadway support, resulting in different mechanical properties from those of pure coal and rock mass. Accurately obtaining the mechanical properties of coal in coal-rock combined body can help to properly understand the deformation and failure characteristics of the underground coal mass. First, an experimental method to obtain the stress and strain of coal in coal-rock combined samples using strain gauges was proposed and validated. Then, tests on thirteen types of coal-rock combined samples were conducted. The results show that the rock experienced a strain recovery and played a loading effect on the failure of coal when coal-rock samples failed. The compressive strength of coal in the sample increased with the rock strength, and decreased with the coal-rock height ratio. Furthermore, two damage constitutive models of coal were established by serially connecting one damage body with one or two Newton body(s), to reveal the influences of rock(s) on the mechanical behavior of coal in coal-rock samples. Finally, test results were fitted using the two models. It was showed that the two models can accurately describe the stress-strain curves of coal in coal-rock samples and reflect the influences of rock(s), coal-rock combination form and coal-rock height ratio. The fitting constants of the two models have clear physical meanings and can be easily obtained, which are expected to be widely used in underground engineering.
Abstract Automatically formed roadway (AFR) by roof cutting with bolt grouting (RCBG) is a new deep coal mining technology. By using this technology, the broken roadway roof is strengthened, and roof cutting is applied to cut off stress transfer between the roadway and gob to ensure the collapse of the overlying strata. The roadway is automatically formed owing to the broken expansion characteristics of the collapsed strata and mining pressure. Taking the Suncun Coal Mine as the engineering background, the control effect of this new technology on roadways was studied. To compare the law of stress evolution and the surrounding rock control mechanisms between AFR and traditional gob-side entry driving, a comparative study of geomechanical model tests on the above methods was carried out. The results showed that the new technology of AFR by RCBG effectively reduced the stress concentration of the roadway compared with gob-side entry driving. The side abutment pressure peak of the solid coal side was reduced by 24.3%, which showed an obvious pressure-releasing effect. Moreover, the position of the side abutment pressure peak was far from the solid coal side, making it more beneficial for roadway stability. The deformation of AFR surrounding rock was also smaller than the deformation of the gob-side entry driving by the overload test. The former was more beneficial for roadway stability than the latter under higher stress conditions. Field application tests showed that the new technology can effectively control roadway deformation. Moreover, the technology reduced roadway excavation and avoided resource waste caused by reserved coal pillars.
As the work hardening rate increases during the cold drawing of non-heat-treated steel (NHT steel), a significant loss in ductility and toughness can occur, leading to reduced formability and part quality. In this study, a bidirectional drawing process consisting of alternating forward and reverse passes is proposed to mitigate these issues and enhance the mechanical performance of the steel. Mechanical property evaluations, including tensile testing and three-point bending tests, were conducted to assess the effects of bidirectional drawing compared to conventional unidirectional drawing. The results showed that the bidirectionally drawn wire maintained a similar tensile strength to that of the unidirectionally drawn wire at a 70% area reduction, while exhibiting a 12% improvement in elongation. Microstructural analysis revealed grain refinement and reduced texture anisotropy in the bidirectionally drawn specimens, contributing to the observed enhancement in ductility. These findings indicate that bidirectional drawing is a promising approach for improving the formability and overall quality of high-strength, NHT steel components.
Abstract The roadway support has always been a difficult problem in the mining engineering, especially in the deep soft rock roadway, whether it can provide endurable and effective support directly affects the safety production and sustainable development of the mine. In order to solve the supporting issues, it is necessary to make the deformation failure mechanism of deep soft rock roadway clear. This paper describes a case study of the deformation failure mechanism and support technology of deep roadway with soft rock mass in No.2 mine zone of Jinchuan mine that is located in Gansu Province, China. Based on a detailed field investigation and previous research experience, the modes, influencing factors, laws and mechanisms of deformation failure in the roadway are summarized. Then the primary combined supporting scheme “double layer bolt-mesh-shotcrete and U-shaped steel” is evaluated through numerical simulation calculation and onsite experiments. To make up for the shortcomings of the primary support, an improved combined supporting scheme “double layer long bolt-mesh-shotcrete and CFST (concrete filled steel tube)” is proposed. The results of numerical simulation, field monitoring and economic analysis show that the new support can control the deformation of the roadway effectively and has a high cost performance. Finally, several suggestions for supporting in deep soft rock roadway are put forward, aiming at serve as a reference for other engineering.
Water inrush disaster is one of the most threatening disasters in the process of deep coal mining, coal under the action of mining stress to produce damage fractures to form seepage paths, groundwater through these seepage paths into the working face to cause water inrush disasters, different mining methods caused by different damage degrees and fracture distribution, resulting in different distribution of seepage paths, directly affecting the risk of water inrush. Therefore, the damage characteristics and seepage path distribution of deep coal under three mining modes: protective layer mining (PCM), top coal mining (TCM) and pillarless mining (NM) were systematically studied through the triaxial seepage test with axial and confining pressure cycles, and the three-dimensional fracture scanning with a high-precision scanner. The results show that the high stress loading amplitude (NM>TCM>PCM) significantly aggravates the deformation of coal samples and drives the hysteresis loop to change from sparse to divergent, and the strain mutation of TCM and NM in the late cycle indicates the risk of instability. The damage accumulation rate of TCM and NM was significantly higher than that of PCM, and the damage degree of the rupture surface became more serious. The permeability increased in stages with the increase of stress level, and the high stress loading amplitude promoted the fracture propagation and penetration, which significantly optimized the connectivity of the seepage channel. The seepage paths of PCM, TCM and NM showed bifurcation tree, network and surface shape, respectively, and the seepage effect increased sequentially. This study provides a reference for the damage control and prevention of water inrush in deep coal.
Current research on gas concentration prediction in working faces of coal mines often suffers from limited feature dimensions and small dataset sizes, making it difficult to extract long-term fluctuation patterns from large-scale time-series data. To address this issue, this study proposes a Principal Component Analysis (PCA)-Transformer-based prediction algorithm for gas concentration in working faces. Firstly, raw gas concentration-related data was cleaned and normalized using min-max scaling. Then, PCA was applied to reduce the dimensionality of seven influencing factors (methane concentration at the upper corner, return airflow methane concentration, oxygen concentration, carbon monoxide concentration, temperature, net flow rate, and wind speed), effectively eliminating weakly correlated features. Finally, the processed training set was fed into a Transformer model, where the encoder and decoder extracted intrinsic patterns and features of gas concentration variations. Using monitoring data from working face 224 of a high-gas mine in Tongchuan as a sample, the PCA-Transformer model was compared with Long Short-Term Memory (LSTM), PCA-Long Short-Term Memory (PCA-LSTM), and Transformer models. The results show that: ① The PCA-Transformer model achieves a Mean Absolute Error (MAE) of 0.020 3, Mean Squared Error (MSE) of 0.047 2, and a runtime of 86 seconds, meeting the accuracy and timeliness requirements for gas concentration prediction in coal production. ② Compared to LSTM, PCA-LSTM, and Transformer models, the PCA-Transformer model better fits gas concentration trends, effectively identifies peak and trough sequences, and requires the least computational time, demonstrating its superior performance.
In the history of the city of Barnaul and in the memory of its inhabitants, Pyotr Kozmich Frolov remains, above all, a distinguished and innovative engineer, alongside such renowned figures as Ivan Ivanovich Polzunov and Kozma Dmitrievich Frolov. Researchers have most often focused on his primary field of service — the mining and metallurgical industry and the cast-iron railway. However, Frolov also secured his place in history through his significant contribution to shaping the city’s attractive appearance, as a result of which Barnaul came to resemble St. Petersburg in its outlines. The main objective of the authors is to determine the role that Pyotr Frolov played in forming Barnaul’s appealing image as a “Corner of St. Petersburg” — a center of culture, science, and enlightenment. In many respects, this study is linked to his efforts in the planning and beautification of the city, as well as to the powerful influence of the cultural landscape of Saint Petersburg — the capital of the Russian Empire, where Frolov had studied mining engineering and served, thus becoming well acquainted with the city. Through his decisions and actions in designing Demidov Square, Pyotr Kozmich Frolov enhanced the symbolic status of Barnaul as the center of the region’s mining and metallurgical activities, while simultaneously shaping its cultural and educational image in contrast to the prevailing perceptions of Siberia at that time.
Redouane Oubah, Latifa Ouadif, Youssef Zerradi
et al.
Among surface mining methods, strip mining is a widely used technique for extracting mineral resources. This method is suitable for most near-surface stratiform sedimentary deposits and has historically been linked to surface mining of deposits such as coal, phosphates, and other natural substances. Given the significant economic interest that strip mining represents, it is in the best interest of mining companies to exploit as much of the reserves as possible using this technique, as it offers many advantages compared to open-pit or underground methods, particularly regarding safety and ore recovery rates. Today, the exploited deposits have become deeper, making the strip mining process more complex. Hence, there is a need for certain adaptations and the introduction of new techniques to address these geological conditions that threaten the feasibility of this method. This article explores the challenges that strip mining faces in contexts of thick overburden and subsequently presents the various techniques proposed by researchers worldwide aimed at overcoming these difficulties. The paper is based on an in-depth review of existing literature that deals with case studies of open-cast mines in different contexts. The examination of various approaches and techniques used for optimizing exploitation under thick overburden conditions by strip mining, along with their limitations, is presented.
Abstract In practical engineering, it is a common phenomenon of rocks subjected to cyclic loading. Such as mining engineering, subgrade engineering and earthquake engineering. In order to reveal the deformation properties of rock under cyclic loading and to establish the damage model, two groups of cyclic loading tests are carried out. Natural rocks show a remarkable nonlinear deformation property under the cyclic loading. The test results also reveal the evolutions of the elastic modulus and the residual strain of fractured rock. Energy dissipation is the essential characteristic of rock deformation and failure. Therefore, a damage model for fractured rock is established from the viewpoint of energy dissipation. This model takes into account the initial damage of fractured rocks and introduces the concept of equivalent modulus, which make the model more practical and easier to apply.
This is an article in the field of mining engineering. The effects of reducing agent and dephosphorization agent on the direct reduction of high phosphorus oolitic hematite were reviewed. The research status of the influence of reducing agents on the reduction of high-phosphorus oolitic hematite was summarized from two aspects of coal and other reducing agents, and the research progress of dephosphorizers was summarized from two ways of using single and combined dephosphorizers. The problems existing in the direct reduction-magnetic separation process of high-phosphorus oolitic hematite were pointed out. According to the existing problems, suggestions for the future research direction of direct reduction-magnetic separation of high-phosphorus oolitic hematite were put forward.
Yanzhe Zhao, Li Cui, Vinothkumar Sivalingam
et al.
With the development of the equipment manufacturing industry towards the direction of intelligence, the demand for the use of intelligent materials is increasing, and high-performance shape memory alloy (SMA) products are getting more and more attention. However, the current machining quality of shape memory alloy products can not meet the existing quality requirements. The mechanism of surface integrity of NiTi SMA needs to be revealed. The influence of martensitic transformation on microstructure, roughness, hardness, and superelasticity was explored. The occurrence of martensitic transformation is determined by controlling the cutting speed (lower and higher cutting speeds) and machining conditions (dry and liquid nitrogen conditions). The superelasticity was expressed quantitatively by the remnant depth ratio. The occurrence of martensitic transformation promoted the formation of the affected layer and work hardening. Meanwhile, it is an important reason for the increase in roughness and the decrease in superelasticity.
The current situation and future development trend of the intelligent construction market in coal mines are the focus of attention for industry management departments, coal production enterprises, technology support enterprises, and other potential enterprises. It is also an important guiding direction for capital investment, technology research and development, and talent cultivation in the industry. Construct a six dimensional Porter diamond model based on production factors, demand conditions, supporting industries, enterprise strategies, industry opportunities, and government support policies to macroscopically analyze the competitive advantages of the coal mine intelligent construction market; Based on historical data such as the number of coal mines, production capacity, fixed assets investment in mining and dressing industry, total investment in intelligent construction, and construction results from 2013 to 2023, select data in different dimensions such as quantity indicators, production capacity indicators, and investment indicators, calculate the market penetration rate of intelligent construction of coal mines and perform curve fitting, and further modify the fitted curve according to the concentration of coal enterprise scale, concentration of coal production capacity distribution, and concentration of coal enterprise attributes; To further measure the market vitality of coal mine intelligent construction, taking the first batch of 71 intelligent demonstration coal mines in China as samples, the market capacity of coal mine intelligent construction from 2025 to 2035 is predicted. In the case where it is difficult to obtain comprehensive and accurate market data of all subsystems of coal mine intelligent construction over the years, SAC, SAM, and SAP product market statistical data are used to verify the reliability of coal mine intelligent market analysis and prediction results; Based on policy guidance, technological status, and actual construction, five stages of the development of the coal mine intelligent construction market have been proposed: budding, cultivating pilot projects, demonstration construction, comprehensive construction, and advanced intelligence. Based on the Jeffrey Moore divide theory, the characteristics of each stage of intelligent construction and the characteristics of early and mainstream markets have been analyzed, and the market gap and its factors in coal mine intelligent construction have been explored. Specific measures to bridge the gap have been proposed. China’s coal mine intelligent construction market has strong and sustained competitiveness; The market penetration rate is expected to reach 10% by 2026, with a market penetration rate of approximately 4.74% in 2023. This is a golden period for social capital investment, and lower investment can be used to leverage higher market share in the future; The market capacity for intelligent construction of coal mines is expected to exceed 320 billion yuan by 2025 and reach trillions of yuan by 2035; The current intelligent construction of coal mines is in a gap area between the early market and the mainstream market, and it is expected to cross the gap in 2−3 years.
Vibration disease ranks among the first in the structure of diseases in workers at mechanical engineering enterprises, metallurgical, mining, and construction industries, various branches of agriculture, and aircraft manufacturing. A change in the mental status of people working in vibration conditions was identified; the most common are «neurosislike states» with psycho-emotional disorders of anxiety type. Meanwhile, currently existing data on the state of the nervous system in vibration pathology are contradictory and scarce, which requires a more in-depth study. Purpose of the study: to investigate the psychological status of patients with vibration disease from the action of both local and general vibration. Research results. In patients with vibration disease from the action of both local and general vibration, a predominance of destructive psychological defenses (projection and repression) over constructive ones (compensation and rationalization) is observed.
Abstract In deep underground coal mining, engineering activities are performed within anisotropic in-situ stress fields due to engineering disturbances and tectonic stress. Many such activities involve the development of excavations in soft rock and anisotropic coal. Accordingly, studying the mechanical properties of soft rocks is important for the stability of deep underground excavations. In this study, the deformation, strength, and failure characteristics of soft sandstone and raw coal under two different true triaxial loading paths were investigated using a self-developed true triaxial test apparatus. The results indicated that the inelastic strain in the pre-peak stage of sandstone and coal gradually increased with increasing intermediate principal stress. Also, the strength-drop in the post-peak stage increased. The crack initiation stress, crack damage stress, and peak strength of sandstone and coal first increased and then decreased with increasing intermediate principal stress for a given σ3. Moreover, with increasing intermediate principal stress, the failure mode of sandstone and coal changed from shear to tensile shear, and from brittle to semi-brittle. The linear Mogi criteria as found to characterize the true triaxial strength of coal well, while the modified Lade criteria was more applicable to soft sandstone. Owning to the symmetry assumption, the linear Mogi criteria predicted low strength when the intermediate principal stress coefficient exceeded to 0.5. In addition, the peak strength curve of rock on the π plane and the influence of weak structures on the failure mode of anisotropic coal was discussed. Weak structures have an important influence on the failure mode of coal, which depends on the strength difference between the structural plane and the coal rock mass. The strength envelope on the π plane had a significant stress Lode angle effect, which gradually decreased as the mean stress increased.