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Mineral consumption is increasing rapidly as more consumers enter the market for minerals and as the global standard of living increases. As a result, underground mining continues to progress to deeper levels in order to tackle the mineral supply crisis in the 21st century. However, deep mining occurs in a very technical and challenging environment, in which significant innovative solutions and best practice are required and additional safety standards must be implemented in order to overcome the challenges and reap huge economic gains. These challenges include the catastrophic events that are often met in deep mining engineering: rockbursts, gas outbursts, high in situ and redistributed stresses, large deformation, squeezing and creeping rocks, and high temperature. This review paper presents the current global status of deep mining and highlights some of the newest technological achievements and opportunities associated with rock mechanics and geotechnical engineering in deep mining. Of the various technical achievements, unmanned working-faces and unmanned mines based on fully automated mining and mineral extraction processes have become important fields in the 21st century.

With the increasing depth of mining, rock burst is on the rise. China’s deep mining industry faces such a threat. A major problem of deep mining is high ground stress, which is the major factor of rock burst. Due to the complexity of the rock burst mechanisms, complexity of induced factors as well as suddenness and randomness of rock burst occurrences, studies of rock burst prediction and control for safe mine exploitation is far from satisfying. The purpose of this paper is to examine of rock burst phenomenon in order to understand both stability in rock mechanics and the prediction of instability disasters in rock mechanics for application in the Ivory Coast mining sector with reference to the current Chinese mining industry.

A microseismic monitoring system was installed in an underground room and pillar coal mine in the Eastern United States to analyze the occurrence and characteristics of induced seismicity during the retreat of two panels in the mine. This study is the first microseismic monitoring effort at an underground coal mine in nearly 30 years. During the retreat of the first panel, an array of eight uniaxial geophones, installed 10 ft. into the roof, recorded events and their magnitudes. The second panel was monitored using an array of twelve uniaxial geophones and two triaxial geophones, also installed 10 ft. into the roof. Comparing the results of these studies, it has been found that the magnitude of seismic events is minimally affected by immediate roof geology or depth of cover. However, it was observed in both studies that the rate at which seismic events occurred did vary with changing roof geology and depth of cover. Using the seismic data from the second panel retreat, focal mechanism solutions were generated for 50 hand-picked events in order to determine if the failure was in compression, tension, or shear. Results of the focal mechanism solutions show that stress relief resulting in dilational events occurs at significant depths, 150–200 m in this case, beneath the active mining face.

With the increasing depth of underground coal mining in China year by year, the problems of the floor heave of roadway become more and more serious. As one of the main forms of the deformation and failure of the surrounding rock in the soft rock roadway, floor heave is the most difficult problem to be solved in the deep mining of coal mines and other underground tunnel engineering. In order to control the floor heave effectively, Chinese scholars have systematically studied the treatment methods of floor heave under various conditions. In this paper, the direct reinforcement method, the indirect reinforcement method and the unloading method are analyzed emphatically, and the comprehensive treatment methods of the grouting bolt combined with reinforcing sidewalls and corners for the floor heave are put forward. After the engineering application of the methods of the grouting bolt combined with reinforcing sidewalls and corners in Baode coal mine, the floor heave of the roadway is controlled at 283 mm and the reinforcement cost of roadway floor is reduced by 40%, which has achieved remarkable technical and economic results. Finally, the prevention and control of floor heave technology is prospected.

The article describes the course of design work, leading to the implementation of a new construction of suspended rails rails for the needs of mines belonging to the Jastrzębska Coal Company. The aim of the works, which was one of the stages of the typification of mining excavation equipment within JSW SA, was to improve the material management within the Company, reduce the production costs of rails, improve their anti-corrosion properties and extend the service life of the track. The design of the new construction was also characterized by easy construction, high straightness of the rail and also the possibility of easy adaptation to the increased speed of transport by suspended rail. The overriding objective of all activities is to reduce the cost of extraction. The design work was carried out using a feedback loop, taking into account the necessary corrections in the subsequent stages, resulting from the results of the strength calculations, laboratory tests and comments of the representatives of JSW SA. The final part of the work was the production of a prototype batch of rails, with the load capacity in accordance with the provisions of the applicable regulations, as well as the usable properties corresponding to the needs of mines JSW SA. JSW SA rails, according to the GIG documentation, are available in several variants: straight rails, curved rails, concave or convex rails and transition rails. The JSW rail system is a complement to the JSW rail system, including suspension, pull-outs, turnouts, locks, and track stops from third-party systems that comply with the JSW system's compatibility and compatibility criteria.

For the study on the propagation–attenuation rule of the blasting vibration wave in the deep mining roadway of Shizishan copper mine, and the analysis of the influences of different maximum explosive charges and different underground systems on the propagation of blasting vibration signals, blasting vibration monitoring of the two different situations has been carried out respectively. Firstly, the Sadov’s Formula has been applied to analyzing the monitoring results of the mining roadway, and thus the value of its excavation blasting vibration attenuation index K and $$\alpha $$ and its corresponding regression formula were attained; then, the appropriate regression formula was used to calculate the maximum explosive charge which could ensure the safety of the principal chambers underground the mine. Meanwhile, on the basis of the HHT analysis method, the rule of vibration wave propagation under these two different situations was analyzed. And the results indicated that, whether with an increase in the single charge, or with an increase in the number of the underground systems to cross, blasting seismic wave had a tendency for spreading to the low-frequency band. Through the regression analysis of the Sadov’s Formula and the HHT Method, the results provided a reliable basis for the safe and efficient production of the mine.

Cross-media analysis and reasoning is an active research area in computer science, and a promising direction for artificial intelligence. However, to the best of our knowledge, no existing work has summarized the state-of-the-art methods for cross-media analysis and reasoning or presented advances, challenges, and future directions for the field. To address these issues, we provide an overview as follows: (1) theory and model for cross-media uniform representation; (2) cross-media correlation understanding and deep mining; (3) cross-media knowledge graph construction and learning methodologies; (4) cross-media knowledge evolution and reasoning; (5) cross-media description and generation; (6) cross-media intelligent engines; and (7) cross-media intelligent applications. By presenting approaches, advances, and future directions in cross-media analysis and reasoning, our goal is not only to draw more attention to the state-of-the-art advances in the field, but also to provide technical insights by discussing the challenges and research directions in these areas.

A device for supporting soft rock masses combined with a constant resistance structure characterized by constant resistance and large deformation at the end of a steel bar, known as the constant resistance and large deformation (CRLD) bolt, has recently been developed to counteract soft rock swelling that often occurs during deep mining. In order to further study the mechanical properties of the CRLD bolt, we investigated its mechanical properties by comparison with the conventional strength bolt (rebar) using static pull tests on many aspects, including supporting capacity, elongation, radial deformation, and energy absorption. The tests verified that the mechanical defects of the rebar, which include the decrease of bolt diameter, reduction of supporting capacity, and emergence and evolution of fracture until failure during the whole pull process, were caused by the Poisson’s ratio effect. Due to the special structure set on the CRLD bolt, the bolt presents a seemingly unusual phenomenon of the negative Poisson’s ratio effect, i.e., the diameter of the constant resistance structure increases while under-pulling. It is the very effect that ensures the extraordinary mechanical properties, including high resistance, large elongation, and strong energy absorption. According to the comparison and analysis of numerical simulation and field test, we can conclude that the CRLD bolt works better than the rebar bolt.

The year-after-year deepening of North China-type coal mines has resulted in frequent water inrush disasters at coal seam floors, causing significant casualties and property loss. The key factor for assessing water inrush hazards is the depth at which the coal seam floor will fail. It is therefore of great importance to predict this failure depth so as to evaluate the potential for floor water inrush incidents and establish effective controls in a timely manner. This paper takes a deep-mining mine in North China Coalfield, as an example, a comparative study is made using four methods: theoretical calculation method, back propagation neural network (BPNN) method, field measurement method, and empirical formula method. The results show that the new theoretical calculation method and the back propagation neural network method proposed in this paper are closer to the true floor failure depth under deep seam mining conditions. Therefore, this study has played an important reference role for prevention and control of water inrush from coal seam floor in deep mining.

The copper ore deposit in SW Poland has been excavated for about fifty years by three deep mines owned by the KGHM Polish Copper JSC. Seismic activity and rock-bursts have been accompanying mining operations since the mines were launched. Therefore prevention measures have to be implemented to assess, mitigate and reduce the seismic and rock burst hazards. Seismic activity i.e. the energy and number of tremors is monitored permanently by means of the mine seismological network. The seismic hazard is also controlled with measurements of the convergence of mine workings. The results of the convergence and seismic activity measurements allow for continuous monitoring of rock mass behavior, as they may indicate increased energy accumulation in the rock mass. On this basis, procedures provoking the release of excess energy from the rock mass can be performed, which may limit the occurrence of uncontrolled, and therefore dangerous to people seismic phenomena. This threat results, among others, from the deposit geological structure and tectonics as well as the significant depth of exploitation. The necessity to carry out measurements for assessing the state of the rock mass is stated in legal regulations and internal mine ordinances. The purpose of the paper was to analyze and assess the relationship between the convergence and seismic activity. The investigation covered one mining panel in the Polkowice-Sieroszowice mine and the four-year period.

The backscattering of radar targets is sensitive to the relative geometry between targets' orientations and the radar. This target scattering diversity makes mechanism interpretation and quantitative application difficult. This study reviews a newly established theory for target scattering mechanism interpretation in the rotation domain. It contains uniform polarimetric matrix rotation theory and the interpretation tool of polarimetric coherence pattern. The core idea of the proposed method is to expand targets' information obtained at a specific orientation to the full rotation domain, which can provide fundamentals for the deep mining and utilisation of target scattering information. On this basis, typical applications with the derived new polarimetric features are introduced and the effectiveness of these features is demonstrated.

Coal mine formations are becoming increasingly threatened by water inrush accidents resulting from high-pressure water conditions in limestone formations below mines with increasingly greater mining depths. This paper focuses on the floor of a deeply buried coal seam and the high-pressure fully mechanized mining faces of the Chensilou Coal Mine in China. Based on systematic observations and analysis of the geological and hydrogeological conditions in the study area, this study conducts theoretical analyses, numerical simulations, and underground observations in a comprehensive manner. Accordingly, a systematic and substantive investigation of the deformation and failure of the deep mining floor and the water inrush mechanism (i.e., the high hydraulic pressure within ash-filled fissures) in the Chensilou Coal Mine is carried out. The burial depth is deeper than 761.4 m, and the water pressure in the limestone of the Taiyuan Formation exceeds 4.95 MPa. Furthermore, the mining depth of the working face is 34.25 m. Based on data on water inrush events and subsurface mining failure depth, the water inrush mechanism in the floor of the coal seam in the Taiyuan Formation is analyzed. The end hole depth of the working face is composed of the L8 limestone, and transient electromagnetic detection technology is used to test the grouting effect of the working face floor and ensure the mining safety of the three working faces tested in this study.

The generation of rock bursts is closely related to overburden movement. Particularly in the condition of a hard and thick overlying strata in deep mining, the impact of a rock burst is eve...

Combined with the actual conditions of the middle section of the V# orebody of Xincheng Gold Mine, the criterion, the yield function, and the softening parameter of the double-yield model were studied. And the simulation parameters of the double-yield model were obtained according to the mechanical parameters of the filling body in Xincheng Gold Mine. The FLAC3D numerical simulation method was used to simulate the filling body of first-step mining stage, and the simulation results of the initial and later stages were analyzed. Real-time monitoring equipment was buried in the second layer of the first-step mining stage to get the internal stress-strain law of the filling body. As for double-yield model, the data of the second stratified monitoring, the data of the real-time monitoring, and the data monitored by the Mohr-Coulomb model of the filling body were compared and analyzed. The applicability of the double-yield model in simulating the filling body was verified, which was closer to the results of actual situation. At the same time, the distribution and variation of stress and strain were basically understood. The above analysis results provide a scientific basis for the optimization of deep mining in Xincheng Gold Mine.

The laboratory simulation environment of the low-voltage station area is set up, and various experimental conditions such as adjustable line parameters, variable load, and operating conditions can be simulated to simulate various types of on-site environment and operation status of the actual station area. This paper proposes the electrical characteristics analysis and parameter extraction method based on the user's electricity behavior. Firstly, through deep mining of massive low-voltage station area power data, based on hierarchical analysis, cluster analysis and other algorithms, extract the typical electrical characteristics of the station area and the user's electricity behavior characteristics, build a typical low-voltage station area model, and develop the laboratory environment. Then, a method for extracting the electrical characteristics of the station based on the user's electricity consumption behavior is proposed. Finally, the simulation of hardware equipment and numerical model are modified to fully simulate the running state of typical station. The experimental results show that the simulation platform is helpful for the verification of the research results of low-voltage platform area, such as the operation error check, the relationship between household and transformer, and the line loss.

International audience; TCP/UDP port scanning or sweeping is one of the most common technique used by attackers to discover accessible and potentially vulnerable hosts and applications. Although extracting and distinguishing different port scanning strategies is a challenging task, the identification of dependencies among probed ports is primordial for profiling attacker behaviors, with as a final goal to better mitigate them. In this paper, we propose an approach that allows to track port scanning behavior patterns among multiple probed ports and identify intrinsic properties of observed group of ports. Our method is fully automated based on graph modeling and data mining techniques including text mining. It provides to security analysts and operators relevant information about services that are jointly targeted by attackers. This is helpful to assess the strategy of the attacker, such that understanding the types of applications or environment she targets. We applied our method to data collected through a large Internet telescope (or Darknet).

Current mine automation efforts are not truly “manless” and as such miss the business benefits that a true “manless” mine would afford. There are some conditions and complex orebodies that necessitate truly “manless” operations in certain mining zones and there exists a business opportunity that true “manless” operations present. We have called this “Zero Entry Mining” because no human need enter the mining zone. Zero Entry Mining not only reduces risk exposure to personnel, but can also be a source of added economic value through higher utilization of equipment, reduced services (e.g. ventilation) and increased revenue through access to difficult to mine areas. In deep mining this might, for example, involve exploitation of ore at depth where steep pit walls, or mining underneath unsupported ground which may involve unacceptable risk for personnel to enter the mining zone. Ultimately zero entry mining will enable the complete redesign of mines, mining equipment and mining methods in ways that were not possible if personnel were in the mining zone. This paper discusses the economic benefits of zero-entry mining as well as developments necessary to enable its operations, including the systems integrity and technology support to deliver true zero-entry mining capability.

Roadway floor rock burst is an important manifestation of rock bursts in deeply buried mines. With the increase of mining depth and mining intensity, rock burst disasters in the roadway floor such as floor heaves are becoming more serious. The article investigated the roadway floor severe heave caused by floor rock burst during excavation of the No. 3401 working face, which was controlled by an anticlinal structure and deep mining in Shandong Mine, China. Firstly, by analyzing geological conditions of the working face, roadway support parameters, and characteristics of coal and rock, it was revealed that high tectonic stress and high crustal stress were main causes of the floor rock burst. Secondly, based on the Theory of Mechanics and Theory of Energy, the energy conversion process in the roadway floor was discussed, and the rock burst condition caused by elastic energy in the roadway floor was analyzed. The failure characteristics of roadway-surrounding rock were also inspected, using a borehole recorder. The roof and sidewalls of roadway mainly contained fissures and cracks, whereas cracks and broken areas are distributed in the roadway floor. Finally, based on the deformation and failure characteristics of roadway-surrounding rock, a method termed “overbreaking-bolting and grouting-backfill” was proposed to control roadway floor rock burst. The method was tested in the field, and the results showed that it could effectively control the deformation of roadway floor and rock burst, guaranteeing the stability of roadway floor. This impact control method for the roadway floor can provide a reference for the prevention and control of roadway rock burst in mines with similar geological conditions.

To prevent large tunnel deformations caused by rock bursts or squeezing ground conditions, rockbolts need to satisfy both strength capacity and the required deformability. Currently, energy-absorbing rockbolts, such as the cone bolt and the D-bolt, have been successfully used in deep mining to avoid sudden tunnel collapses. This paper proposes a new energy-absorbing rockbolt, referred to as a deformation-controlled rockbolt (DC-bolt). The performance of the proposed DC-bolt was verified by numerical simulations using discontinuous deformation analysis (DDA) and by prototype laboratory tests. As a result, it is concluded that the DC-bolt possesses both high loading capacity and deformation capacity. Additionally, the DC-bolt can limit rock surface movement when it reaches a certain displacement. Thus, it can be a useful tunnel support for tunnels that are to be excavated in squeezing ground conditions.

As one of the dynamic disasters of deep mining, rockburst significantly affects the safety of underground environment especially at great depth. First, the elastic energy and dissipative energy are deduced to characterize rockburst process separately employing the theoretical analysis and test technique. Then, a series of split-Hopkinson pressure bar system tests are conducted. After calculation, the percentage of fractured dissipative energy occupied in total input dynamic energy is obtained. Subsequently, the dynamic mechanical parameters of rock specimens and dynamic impact factors are fitted. Finally, a three-dimensional model is developed using the mechanical property of the host rock, constitutive model, and in situ geostress. The contours of energy and the damage conditions of host rock are predicted, and the tendentiousness of rockburst is estimated Refereed/Peer-reviewed

Cross-modal retrieval usually fills the semantic gap between different modalities by sharing subspaces. However, existing methods rarely consider that the data in a certain modality may be heterogeneous when mapping multimodal data into a shared subspace. In addition, most existing methods focus on semantic associations between different modalities, while few approaches consider the semantic associations within a single modality. To address the above two deficiencies, we propose a Neighbourhood Encoding (NE) framework that mines the semantic association of data in the same modality, solves the problem of data heterogeneity by improving the semantic expression of a single modality. To verify the effectiveness of the proposed framework, we use two types of recurrent neural networks to instantiate the framework. Experiments show that the instantiated approaches outperform existing advanced methods in both text-to-image and image-to-text retrieval directions.

Existing high-dimensional deep data mining methods have the problems of low precision and high energy consumption. Therefore, a deep mining method of high-dimensional big data based on association ...

In this paper, we propose a procedure for diagnosing diabetic retinopathy and detecting other suspected areas by using Convolution Neural Network (CNN). The paper is divided into two research areas: First is to identify and predict the highly suspicious region in the high-resolution suspicious patches using Deep-in-Net which can generate disease detection accurately. Second is four bounding boxes generated using machine learning technique by automatically reading maps that gives 80% of information of the eyes labelled by experienced ophthalmologist. This technique has good ability to seek attention mapping. The experiment has two datasets, EyePACS and Messidor.

For mining using the caving and filling methods in metal mines, determining a suitable size for the isolated pillars—the connecting part of the extension from shallow to deep—is crucial for ensuring safety and efficiency. Considering actual cases involving deep caving and cut-and-fill mining in the Chifeng Hongling lead-zinc mine in Inner Mongolia, China, the reserved thickness range of the horizontal isolation layer is obtained via theoretical analysis. On this basis, the pre-processing software HyperMesh is used to build a high-precision hexahedral grid model of the mining area, and the three-dimensional geological model of the mining area is imported into the finite-difference software FLAC3D. The stress field, displacement field, and plastic area evolution law of pillars (horizontally isolated pillars and adjacent rib pillars) in the stope of the ninth middle section after excavation are analyzed via numerical simulation inversion of the selected scheme of horizontal isolated pillars. The numerical simulation results show that the scheme employed to retain the upper horizontal isolated pillars in the ninth middle section involves reserving thicknesses of 8 m and 32 m at average ore body thicknesses of 15 m and 35 m, respectively. These results can provide theoretical guidance and a basis for safe and efficient mining of deep metal mines.

The underground environment in deep mines is complicated and the risk of rockburst is high during excavation. Therefore, it is of great significance to study the tendency of rockburst during excavation. At present, scholars from various countries have analyzed rockburst phenomena from the aspects of strength, stiffness, energy, etc., and have proposed various assumptions and criteria. However, these assumptions and criteria often only consider individual factors, which will lead to one-sidedness and limitations. This article takes the deep mining process of a metal mine as the research background. Based on the results of each independent criterion, fuzzy mathematical theory is introduced to evaluate the rockburst intensity and fuzzy comprehensiveness of various types of rocks in the project. The research results show that the multi-criteria comprehensive evaluation of fuzzy mathematics can well integrate the analysis results of each criterion, and has higher consistency with the actual situation in engineering.

Controllable spatial patterning is a major goal for the engineering of biological systems. Recently, synthetic gene circuits have become promising tools to achieve the goal; however, they need to possess both functional robustness and tunability in order to facilitate future applications. Here we show that, by harnessing the dual signaling and antibiotic features of nisin, simple synthetic circuits can direct Lactococcus lactis populations to form programmed spatial band-pass structures that do not require fine-tuning and are robust against environmental and cellular context perturbations. Although robust, the patterns are highly tunable, with their band widths specified by the external nisin gradient and cellular nisin immunity. Additionally, the circuits can direct cells to consistently generate designed patterns, even when the gradient is driven by structured nisin-producing bacteria and the patterning cells are composed of multiple species. A mathematical model successfully reproduces all of the observed patterns. Furthermore, the circuits allow us to establish predictable structures of synthetic communities and controllable arrays of cellular stripes and spots in space. This study offers new synthetic biology tools to program spatial structures. It also demonstrates that a deep mining of natural functionalities of living systems is a valuable route to build circuit robustness and tunability.

Deep mining operations require special measures in order to keep safe and economic aspects. After mine ore is extracted, voids are created and need to be filled with high-strength, low-cost materials. Cemented Paste Backfill (CPB) has recently become one of the main alternatives in filling stopes. Although numerous papers have mentioned the magnitudes of the strength of this material, its behavior under high confining pressures is still not well understood. Therefore, the purpose of this study is to increase the knowledge regarding the CPB behavior. Triaxial compression tests were performed using a Hoek Cell and Load Frame System under high confining pressures. Samples with two different binder contents were used in order to obtain the CPB strength improvement. Besides the self-weight consolidation curing method, samples were subjected to a different curing method that simulated a zero gravity condition (rotating wheel) in the first curing day to compare their mixture properties. The results suggested that both curing method and binder content have influenced the geomechanical properties of Cemented Paste Backfill. By increasing the curing time, the CPB shear strength has increased slightly, whereas specimens with higher binder content presented a significant increase in shear strength values.

Cooling energy needs, for mines in Northern Ontario, are mainly driven by the mining depth and its operation. Part I of this research focusses on the thermal energy loads in deep mines as a result of the virgin rock temperature, mining operations and climatic conditions. A breakdown of the various heat sources is outlined, for an underground mine producing 3500 tonnes per day of broken rock, taking into consideration the latent and sensible portions of that heat to properly assess the wet bulb global temperature. The resulting thermal loads indicate that cooling efforts would be needed both at surface and underground to maintain the temperature underground within the legal threshold. In winter the air might also have to be heated at surface and cooled underground, to ensure that icing does not occur in the inlet ventilation shaft-the main reason why cooling cannot be focussed solely at surface. Keywords: Thermal loads, Cooling, Underground mining, Deep mining, HVAC mining

The classification of imbalanced data has been recognized as a crucial problem in machine learning and data mining. In an imbalanced dataset, there are significantly fewer training instances of one class compared to another class. Hence, the minority class instances are much more likely to be misclassified. In the literature, the synthetic minority over-sampling technique (SMOTE) has been developed to deal with the classification of imbalanced datasets. It synthesizes new samples of the minority class to balance the dataset, by re-sampling the instances of the minority class. Nevertheless, the existing algorithms-based SMOTE uses the same sampling rate for all instances of the minority class. This results in sub-optimal performance. To address this issue, we propose a novel genetic algorithm-based SMOTE (GASMOTE) algorithm. The GASMOTE algorithm uses different sampling rates for different minority class instances and finds the combination of optimal sampling rates. The experimental results on ten typical imbalance datasets show that, compared with SMOTE algorithm, GASMOTE can increase 5.9% on F-measure value and 1.6% on G-mean value, and compared with Borderline-SMOTE algorithm, GASMOTE can increase 3.7% on F-measure value and 2.3% on G-mean value. GASMOTE can be used as a new over-sampling technique to deal with imbalance dataset classification problem. We have particularly applied the GASMOTE algorithm to a practical engineering application: prediction of rockburst in the VCR rockburst datasets. The experiment results indicate that the GASMOTE algorithm can accurately predict the rockburst occurrence and hence provides guidance to the design and construction of safe deep mining engineering structures.

The cutting efficiency in underground excavations relies on the optimum parameters of the cutting tool and the cutting process. However, the optimization of the cutting tool design and the cutting process is a challenge and requires knowledge about the tool-rock interaction. This paper aims to investigate the tool-rock interaction using a rock cutting mathematical model. The confining pressure was considered in the rock cutting model with conical cutters and the discrete element method was adopted to calculate the dynamics of the rock breakage of this model. Graded particle assemblies were created, calibrated, and compressed in the horizontal direction with a certain confining pressure. Afterwards, the initiation and propagation of cracks during the rock cutting processes were recorded. A series of small-scale rock cutting tests were also carried out to verify the numerical model. The analysis results demonstrate that: 1) the confining pressure induced larger cutting force than that in the unconfined condition; 2) with increase of the confining pressure, the rock failure mode experienced predominantly brittle to predominantly ductile failure; and 3) there was a critical confining pressure/compressive strength ratio of 0.53 when the transition of failure mode occurred.

Workers exposed to hot and humid conditions suffer from heat stress that affects their concentration and can potentially lead to an increase in workplace accidents. To minimize heat stress, protective equipment may be worn, such as personal cooling garments. This paper presents and discusses the performances, advantages and disadvantages of existing personal cooling garments, namely air-cooled, liquid-cooled, phase change, hybrid, gas expansion and vacuum desiccant cooling garments, and a thermoelectric cooling technology. The main objective is to identify the cooling technique that would be most suitable for deep mining workers. It appears that no cooling technology currently on the market is perfectly compatible with this type of mining environment. However, combining two or more cooling technologies into a single hybrid system could be the solution to an optimized cooling garment for deep mines.

For urgent solutions to existing major engineering problems such as deep mining and deep burial of high level radioactive nuclear wastes, exploring the mechanical behaviors of rocks under the synergistic effect of the burial depth of rocks and temperature is of great significance. The mode-I fracture characteristics of granite specimens in the semi-circular bending (SCB) test under the effects of different temperatures and burial depths were experimental investigated. The test results showed that the mineral compositions and fracture characteristics of granite both varied significantly at different burial depths in Daliuhang Gold Mine in Yantai, Shandong Province, China. The high-temperature effect would remarkably weaken the influence of the burial depth on the fracture characteristics of granite; moreover, increasingly growing temperature gradually became a dominant factor influencing the fracture characteristics of granite. As the temperature rose from 20 °C to 900 °C, the peak strength, fracture toughness and fracture energy of granite at different burial depths all declined with the temperature rise. Additionally, a significant quadratic polynomial function relationship was found in temperature with peak strength and fracture toughness. Additionally, it was macroscopically found that the fracture energy linearly increased with the fracture toughness, implying that the specimens with larger fracture toughness need to consume more energy during the failure. However, the specific proportions and rates of energy consumption differed in different fracture stages of granite.

Current technical knowledge on the rheological behavior of cemented paste backfill (CPB) that contains nano-silica (nS) at different curing temperatures is insufficient. However, the assessment and an understanding of the yield stress and viscosity of CPB with nS added at the early ages are critical for using CPB technology in underground mines located in cold or warm regions and/or for deep mining. Therefore, the aim of this study is to investigate and develop a better understanding of the combined effects of temperature, addition of nS as an additive, and type of binder on the rheological properties of CPB. To this end, several CPB samples with different compositions are subjected to various temperatures (2 °C, 20 °C, and 35 °C) for up to 4 h. The yield stress and viscosity of the CPB samples are then measured at different time intervals of 0 min, 15 min, 1 h, 2 h, and 4 h. Moreover, electrical conductivity (EC) monitoring, and microstructural analyses (TG/DTG and XRD) are conducted on the samples. It is found that the yield stress and viscosity of the samples cured at 35 °C are much higher than the other samples. The enhancement of the rheological properties of CPB due to the coupled impacts of nS as an additive and higher temperature leads to reduced flowability of the paste. However, it is also found that the addition of a superplasticizer can partially compensate for the fluidity. Also, an increase in the water content reduces the yield stress and viscosity. The findings presented in this paper will contribute to the development of nano-CPB technology and its effective application in the backfilling operations of underground mines.

Deep mining is an inevitable future trend involving resource acquisition. However, as mining depth increases, the high geostress and severe mining disturbance lead to prominent rock burst disasters. At present, the design of deep mines is mainly based on the engineering experiences based on shallow mining. To date, no integrated planning has been implemented for deep mining in domestic mines. Moreover, during the deep mining process, most problems are handled and solved only after the disaster happens due to the lack of understanding of deep disaster problem. In this paper, a large-scale 3D numerical model was established by Map3D software by considering the high geostress environment, the physical and mechanical parameters of rocks, the constitutive model, and preliminary design parameters Based on this model, the disturbance coefficient and energy accumulation state of stopes was predicted, and the rock burst risk was evaluated. According to the analysis results, the medium-deep hole sublevel open stopping method was chosen to reduce the rock burst risk during deep mining. Through the integrated planning of deep mining, the risk of rock burst disasters can be evaluated ahead of time, thus facilitating the use of a more scientific and reasonable mining method in the field of mining engineering. Integrated planning provides a new method for deep mining and can also and can help reduce or even control fundamentally the magnitude and frequency of rock burst disasters. Thus, it has great security and economic significance for mining engineering.

Pingdingshan mining area is one of the typical deep mining areas in China, and most of the mines in this area are troubled by the difficulties of the deep-soft-rock roadway support. Based on the concept of synergistic interactions of the interior and exterior bearing structure of the surrounding rock and, considering the specific geological conditions of the research site, we establish the mechanical model of the interior and exterior bearing structure of the roadway. Based on numerical simulation, we reveal the influence of main factors, such as support strength and mechanical characteristics, of surrounding rock on the distribution and evolution of the interior and exterior bearing structure. We found that increasing the support strength and mechanical parameters of surrounding rock can make the exterior bearing structure close to the roadway enhance the bearing characteristics of the interior and exterior bearing structure and improve the roadway stability. The distribution characteristics of the interior and exterior bearing structure of the roadway under six different support strengths and six different grouting parameters were systematically investigated by field measurements. According to the field test results, an effective strategy for controlling the deep-soft-rock roadway is proposed, which provides a good reference for surrounding rock control of the deep-soft-rock roadway in the Pingdingshan mining area and mines with similar mining conditions.

Temperature has critical influences on rock strength. It is almost universally acknowledged from laboratory studies that rocks are weakened at elevated temperatures, as a result of the various “thermal damage” mechanisms. Most underground projects, such as geothermal energy extraction, nuclear waste repository and underground excavation for deep mining and caverns, are implemented at the depths ranging only from hundreds to thousands of meters where the temperature is far from reaching the high level for the sole operation of the thermal weakening factors. On the contrary, some experimental studies have reported that rock can be strengthened upon heating, rather than weakened in the mild temperature range from room temperature to 200 °C. Despite the profound scientific and practical significance in the geophysical and geological fields, whether rock will be strengthened or weakened in response to elevated temperature is elusive. The mechanisms behind the strengthening effect are also poorly understood. We carry out a comprehensive literature review on laboratory experimental results of the temperature effect on rock strength, with a focus on the mild temperature regime. We find that the dual effects of three major mechanisms and their interplay may either increase or decrease rock strength. Nevertheless, rock strengthening is more or less an intrinsic property depending on various factors. We also find that there exists a “transition period” at elevated temperatures from rock strengthening to weakening. This discovery is important for underground engineering projects, since the determination of a number of design parameters relies on the laboratory-measured rock strength. Misinterpreted temperature impact on rock strength in an engineering project potentially leads to structural and/or economical failure. For accurate evaluation of rock strength, future laboratory studies should concentrate on the mildly heated rock relevant to the in situ ground conditions.

The high levels of heat and humidity in ultra-deep mining raise issues regarding the occupational health and safety of miners as well as productivity. Miners could wear a cooling vest to reduce heat strain, but it would need to be properly adapted to the constraints and requirements of deep and ultra-deep mines. This article examines the first phase of a validation of a previously proposed usability matrix composed of 16 ergonomic criteria via expert elicitation (from both the academic and mining sector) and lab experiments with human participants in a controlled environment. A questionnaire was used to ask experts to prioritize the criteria and determine which of these should be combined, rejected or added. Laboratory participants were asked to execute typical mining movements to assess a number of criteria for two different cooling vests (one prototype and one commercially distributed) and complete a questionnaire containing a 6-point Likert scale for five criteria: fit, comfort, ease of movement, usability and design aesthetics. Eight experts and ten laboratory participants completed their respective questionnaires. The usability matrix was improved and structured into a mind map representing all relevant criteria and their relationships. This mind map will need to be tested further with experts and miners to ensure and complete its scientific validity.

Research on the mining-induced mechanical behavior and microcrack evolution of deep-mined coal has become increasingly important with the sharp increase in mining depth. For rock units in front of the working face, the microcrack evolution characteristics, structural characteristics, and stress state correspond well to mining layouts and depths under deep mining. The acoustic emission (AE) characteristics of typical coal under deep mining were obtained by conducting laboratory experiments to simulate mining-induced behavior and utilizing AE techniques to capture the variation in AE temporal and spatial parameters in real time, which provide an important basis for studying the rupture mechanisms and mechanical behavior of deep-mined coal. The findings were as follows: (1) AE activity under deep mining was characterized by three stages, corresponding to crack initiation, crack stable propagation, and crack unstable propagation. As the three stages proceeded, the AE counting rate and AE energy rate presented stronger clustering characteristics, and the cumulative AE counting and cumulative AE energy exhibited a sharp increase by an order of magnitude. (2) The crack initiation and the main stages of crack propagation were determined by characteristic points of variation curves in the AE parameters over time. In the main crack propagation stage, the number of cumulative AE events and the cumulative AE counts were similar among the three mining conditions, while coal samples under coal pillar mining released the largest amount of AE energy. The amount of accumulated AE energy released by coal samples increased by one order of magnitude according to the sequence of protective coal-seam mining, top-coal caving mining, and nonpillar mining. (3) Fractal technology was applied to quantitatively analyze the AE spatial evolution process, showing that the fractal dimension of the AE location decreased as the peak stress increased, corresponding to protective seam mining, caving-coal mining, and nonpillar mining. The above results showed that the deformation and fracture characteristics of coal under deep mining followed a general law, but were affected by different mining conditions. The crack initiation and main rupture activity of coal occurred earlier under the conditions of protective seam mining, top-coal caving mining, and nonpillar mining, successively. Moreover, nonpillar mining induced the strongest and highest degree of unstable rupture of the coal body in front of the working face.

The sustainable and clean mining of coal is essential for Australia and the world as coal is a key energy source. However, with the increase of mining depth, many coalmines are facing potential coal burst hazards as deep mining always associated with high gravitational stress and complicated geology. More recently, the coal burst risk is highlighted by accidents happened at Austar and Appin coalmines in Australia. Assumedly due to long time mining history with relatively shallow mining depth, coalmines in Australia has no coal burst history and corresponding risk controlling plans, technics and equipment. This paper proposes a novel method for coal burst risk prediction based on fractal dimension analysis of AE spatial distribution. Besides, this paper introduces the mathematical analysis method of fractal dimension based on dimension calculation formula and MATLAB coding. Finally, obvious fractal dimension decrease of AE spatial distribution is observed in experimental study of coal samples with high burst propensity, which promises the feasibility of coal bursts prediction through AE monitoring.

The excavation of deep mining roadways with traditional mining methods leads to various issues, such as the occurrence of large deformations, the waste of coal resources, complex conditions and the high cost of advanced support measures. In this study, we examined the roadway damage mechanism of the traditional gob-side entry driving method with coal pillars using the Suncun Coal Mine, the deepest mine in China, as an engineering case study. A method for the automatic formation of roadways in deep mining areas by roof cutting with high-strength bolt-grouting was proposed, and several quantitative evaluation indicators, namely, the roadway deformation control rate, anchor cable strength utilization ratio, and hydraulic prop strength utilization ratio, were established. The impacts of controlling the deformation of the surrounding rock were comparatively analysed in consideration of numerous factors, such as the mechanical parameters of the surrounding rock, roof cutting height, roof cutting angle, grouting anchor cable length, and hydraulic prop spacing. On this basis, the proposed method was applied in the field. The results showed that the automatically formed roadway cross-section exhibited decreased convergence deformation; moreover, the roof deformation was effectively controlled, and the passive hydraulic prop supports could be effectively replaced with the active support of grouting anchor cables, verifying the effect of the proposed method.

In this paper, the similarity material model is conducted to investigate the movement law and failure pattern of the super-thick weak cementation overburden. In addition, the photographing scale transformation-time baseline parallax (PST-TBP) method and the Xi’an Jiaotong University Digital Close-range Industrial Photogrammetry System (XJTUDP) software were used to monitor similarity material model. The findings can be summarized as follows: (1) To some extent the PST-TBP method can make up for the deficiency of the XJTUDP software because its measurement accuracy is about 0.5mm; (2) The first breaking span of the immediate roof reached 240m, and the cyclic fracturing length was about 60m. It still shows the characteristics of the inadequate mining when the surface reaches fully mining. It needs more mining space to reach fully mining; (3) The (PST-TBP) method and the XJTUDP measurement system provide technical support to study the dynamic development process of regional deformation caused by deep mining.

This paper uses the RFPA numerical simulation software to establish a numerical model of the rheological failure of the rock mass under stress. Rheological failure characteristics of the body was researched, and the results shows: (1) The rupture sequence of rock rupture is from the corner to the middle. When the rock loses stability under pressure, the rock often ruptures from the corner. The corner gradually collapses and cracks. Then the cracks spread to the middle of the rock. Many cracks extending from the corners are in the rock. The central part intersects each other and eventually causes the rock to break. (2) Rock samples of different lithologies have different stress values when they break under the same confining pressure. From the experimental process, we know that granite>sandstone>mudstone. Therefore, the higher the strength of the rock, the harder the rock will be broken. (3) The weaker the plasticity at rupture, the stronger the brittleness and the stronger the sudden change of rupture. In the deep mining process, the greater the confining pressure, the more obvious the rheological characteristics of the rock, and the greater the total energy released during the rock failure process.