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This paper explores the safety of surface structures over a deep coal seam (12#) in a coalmine of northern China's Hebei Province. If 12# coal seam is mined by block caving, the surface might collapse and the surface structure could be damaged. First, FLAC3D simulation was conducted to simulate the influence of block caving in 12# coal seam and the shallower 9# coal seam on roof movement. The results show that the mining of 9# coal seam does not affect surface safety; but the mining of 12# coal seam would cause the surface deformation to exceed the requirements of the current regulation, posing a threat to the safety of surface structures. Hence, the excavation method for the coal seam was replaced with cut-and-fill mining. Further simulation on this coal seam indicates that the safety of surface structures could be guaranteed, when the equivalent mining thickness (EMT) was 0.2m. Under EMT=0.2m, the fill strength that best protects the surface structures and controls the surface deformation was found to be 0.5 times of coal strength. Finally, the EMT and fill strength for the cut-and-fill mining of 12# coal seam were optimized as 0.2m and 0.5 times of coal strength, respectively, laying a scientific basis for fill preparation. [ABSTRACT FROM AUTHOR]

With the increasing depth of underground engineering, the risk of coal–rock dynamic disasters such as rockburst is becoming more and more serious and complex, which seriously threatens the safety of coal resource, mine production and the surface ecological environment. However, the existing risk indices and methods used for evaluating rockburst risk cannot be fully applied to deep goal seam group (DCG) mining. For the safe exploitation of coal resources, in this paper, based on statistical analyses of 300 cases of rockburst, six new indices are proposed for evaluating rockburst risk in the DCG, namely dip angle, moisture content, stability of coal seam, advancing speed of working face, disturbance factors and support patterns. In addition, the influence of multiple factors coupling and superposition on rockburst risk was considered. Thus, the Comprehensive Index Method of rockburst risk of Deep Coal seam Group (DCG–CIM) based on analytic hierarchy process was established. Finally, rockburst risk in the evaluation area was quantitatively assessed into four grades, including "No rockburst risk", "Weak rockburst risk", "Medium rockburst risk" and "Strong rockburst risk". Taking the 2233 working face of Hengda Coalmine as an example, the evaluation results show that the ranges of 0–184 m, 224–284 m, 324–384 m, 424–484 m, 524–584 m and 594–624 m from terminal line of haulage roadway on 2233 working face were the medium rockburst risk zones, which are in accordance with the on-site impact damage results and are more accurate than the traditional method. The DCG–CIM can consider more inducing factors and obtain more accurate and reliable evaluation results and is more suitable for deep coal seam group mining. [ABSTRACT FROM AUTHOR]

In view of the serious damage of roadway and the severe roof weighting of the 3302 working face, microseismic monitoring and surrounding rock displacement monitoring system were used to conduct on-line in-situ monitoring. In this paper, the energy distribution and microseismic event distribution of stope in the primary impact stage and the "square" stage (The working face is pushed to the stage where the strike length of the mined-out area is equal to the dip length, i.e., the stage of "square" of the working face.) are studied. On this basis, the deformation and failure law of the roadways is analyzed. Furthermore, the breaking regularity of multiple thick and hard strata with fully mechanized top-coal caving is obtained. Due to the high span of the fully mechanized caving face, the failure region of the overlying strata expands. As the fracture of the 3rd hard layer, the rotation and deformation of the upper rocks expand. With the periodic fracture of the 3rd hard layer, the hanging area of the 6th hard rock layer increases, which finally leads to its fracture. The weighting of stope is severe during the "square" stage, which is recorded through field monitoring. Through the preliminary analysis, it is concluded that the fracture of the 3rd and the 6th hard stratum contribute to the severe weighting during the "squire" stage, which is easy to induce rock burst. Over the primary impact period, the occurrence of seismic events is frequent and the ground pressure is strong. The maximum approach between two sides of roadway is about 750 mm, and that between the top and bottom is 1300 mm. The periodic weighting of three different "source points" is analyzed by numerical simulation. It is found that the peak value of leading abutment pressure in "square" stage is 82.09 MPa. Finally, the high risk zone of rock burst is obtained, and the predictable "pressure relief zone" is determined, which provides an important reference value for the prevention of rock burst in multi-layer thick and hard rock strata in a super kilometer deep well. [ABSTRACT FROM AUTHOR]

Coal is one of the fundamental fossil energy supporting the world’s economy. The synergistic development between efficient coal mining and ecological environment protection is the inevitable requirement for the preservation of global harmony. As the world’s largest coal producer, China has conducted a strategic shift from east to west in terms of the exploitation of its energy resources, posing a serious threat to the fragile ecological environment of the western region. In particular, the surface subsidence caused by coal mining is the root of the ecological deteriotation and the destruction of ground structures. However, it is difficult to reveal the law of large-scale surface subsidence in western mining areas merely by conventional measurement methods such as leveling, on account of the high intensity of coal seam mining, the weakness of the lithology of overlying rock and the large thickness of wind-blown sand strata. In view of this, small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) technology was used in this study to obtain the time series of surface vertical displacement during the whole mining process of the 2401 working face in the Yingpanhao coal mine, Inner Mongolia. Based on the deformation data, the dynamic evolution characteristics of surface subsidence under high intensity mining in the western mining area were analyzed exhaustively. It was found that the surface subsidence is characterized by an extensive coverage range (48.52 km2) with minimal ground settlement (250 mm) in the study area. Meanwhile, the boundary shape of the subsidence basin followed a “circular-parallelogram-trapezoid” changeable process and the coverage area of the basin experienced three stages: a linear increasing period, a temporary stagnation period, and a re-expansion period. Furthermore, there existed an abnormal uplift phenomenon on the east side of the open-off cut in the 2401 working face. Combined with the structure of overlying strata, this paper carried out a preliminary analysis on the reasons of the abovementioned phenomenon. The research results are of vital realistic significance for ground buildings and ecological environmental protection in the aeolian sand mining area in Western China.

To study the mining stress evolution law of inclined backfilled stope in deep mining, this paper first proposes a method for determining the parameters of the brittle-ductile transition model corresponding to the Hoek–Brown criterion and Mohr-Coulomb criterion under high geostress. Then, a model composed of inclined backfilled stopes with different depths is established to simulate the sequential mining process of ore bodies with varying depths from shallow to deep. The numerical model’s stratum displacement, rock mass stress distribution, and risk factors show that the mining-induced stress will move to the upper stopes and the stratum below the deepest stope. The transfer range and influence degree of mining-induced stress will increase with the increase of the deep mining, resulting in the most dangerous backfilled stope occurring one to two layers above the deepest stope and the apparent stress concentration area occurring below the deepest stope. To prevent disasters caused by mining stress, pillars in inclined deep stopes should have large safety factors. Replacing low-strength backfills with high-strength backfills can reduce the stress concentration in the stratum below the deepest stope.

At present, the increasingly prominent mental health problems of college students have gradually become the focus of the society, universities and families. According to the current situation and challenges of mental health work of college students, we put forward the idea of constructing an early warning platform for college students' psychological crisis based on deep neural networks. The purpose of constructing this platform is to comprehensively improve the psychological health of college students and to purposefully prevent and intervene the psychological crisis. In this paper, we focus on describing the structure, composition of proposed platform and functions of each module, and then give a specific framework, training and testing scheme for the core part of the platform, which is the neural network model for real-time monitoring and analysis of students' mental health. Finally, we demonstrate the effectiveness of the deep neural network for analyzing behavior patterns through simulation experiments on the generated data set. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Nonferrous Metals (Mining Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Water inrush disasters from the coal seam floor occur frequently due to the high water pressure of the Ordovician limestone aquifer, multiple aquifers and strong mining disturbance. We presented a model of water-resisting key strata (WRKS) to investigate the mechanism of floor water inrush from multiple aquifers in deep coal mines. Roof hydraulic fracturing (RHF) for controlling floor water inrush and multi-parameter monitoring were proposed and validated in the Xingdong coal mine in Xingtai, Hebei Province. The results indicated that the periodic weighting step of the test working face after RHF was 9.53 m, which was 61.42% less than that of the working face without RHF (24.7 m). The floor failure depth was 30 m, which was 34.4% less than that of the zones without RHF (45.7 m). Hydraulic fracturing weakened the strength of the overlying strata to control the weighting step and reduce the mining disturbance stress, and the stability of the floor WRKS was enhanced, thereby preventing water inrush from the coal seam floor. The research results provide a solution for preventing floor damage and floor water inrush under strong mining disturbance and in complex hydrogeological environments in deep mining.

In view of problems of high gas pressure and poor permeability of outburst coal seam, unsatisfactory of outburst elimination effect of regional gas control, slow speed of coal roadway excavation and tension of working face replacement caused by deep mining on 15-17220 working face in the Twelfth Coal Mine of Pingdingshan Tia'an Coal Mining Co., Ltd., a regional gas control scheme of 'crossing boreholes + hydraulic punching' was proposed, and the regional gas control effect was tested and verified. The following conclusions are obtained: residual gas content and pressure are reduced to 5.57 m3/t and 0.40 MPa, they are lower than threshold of outburst prevention regulation, which achieve outburst prevention standard for coal mine safety mining; drilling cuttings and borehole gas emission initial velocity respectively are reduced to 3.5 kg/m and 2.18 L/min, the indicators are not overweight, so as to eliminate outburst danger of coal seam; coal roadway excavation footage is risen every month steady with 10%, and effectively relieves problem of tension of working face replacement. The control results validate rationality of the regional gas control scheme.

Energy-absorbing rockbolt is now recognized as an important support element in deep mines around the world. A novel kind of energy-absorbing bolt called J-bolt was developed, which consists of anchoring (damping) module, deformation module, blending module and thread segment. The static pulling loading model and dynamic impact constitutive model of J-bolt were established. The experiment results show: (1) the static pulling load is greater than 190 kN; (2) under multiple dynamic impact loading condition, the peak load of J-bolt exceeds 250 kN each time. Under the given initial dynamic impact loading condition, with the increasing of damping ratio, the oscillation amplitude of J-bolt attenuates quickly along the bolt axial impact direction. The greater the damping effect of J-bolt, the more quickly releasing of the dynamic impact energy. The absorbed energy of J-bolt exceeds 19.3 kJ under each dynamic impact, the accumulated energy absorbing capacity reaches 46.5 kJ. Due to the objective existence of joints in rock mass, the bolted rock mass can generate dilatation and tensile failure in the joints surface of rock mass under dynamic impact condition, but the energy-absorbing support system will keep surfaces of tunnels (stopes) stable, which can effectively absorb the kinetic energy induced by dynamic hazards. [ABSTRACT FROM AUTHOR]

A comprehensive analysis method based on numerical simulation, displacement monitoring and digital borehole photography was proposed and employed to analyze the spalling characteristics and damage range. A continuous–discontinuous numerical model was set up, and which was calibrated based on field displacement monitoring data from Hongtoushan copper mine, and a developed continuous-discontinuous element method (CDEM) coupling the finite element method and the discrete element method was used to investigate the spalling initiation and propagation in the deep underground ramp under periodic stoping conditions, which was verified by the digital borehole photography. The results showed the initiation, propagation of ramp spalling associated with continuous periodic mining-induced stress, and parallels to the vertical stress direction. Severely spalling failure occurs at the left wall of the ramp, and the spalling depth is about 0.6 m. The spalling strain analysis also indicates that large-scale spalling failure occurs in the left wall, and which was verified by the digital borehole photography observation. The numerical simulation and field observation have good consistency. The comprehensive analysis method provide more realistic results, which helps to understand spalling failure mechanisms in deep hard rock mining and provide references for rock support. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The evolution of rock mass cracks is particularly important for the study of the rock mass fracture instability and catastrophic mechanism of underground engineering. To investigate the fracture characteristics of deep rock mass and formation mechanism of the water inrush channel and based on the real measured data of water-inrush mines, this paper divides floor mining cracks into shear cracks, layer cracks, and vertical tensile cracks according to the location of the cracks. Knowledge of mechanics is utilized to analyze the crack-initiating and growing principles of floor mining cracks to disclose the coupling relationship between mining-induced cracks and principle stress and hydraulic pressure. Based on a self-developed simulation test system for high-pressure floor water inrush, a model of crack evolution and channel formation for the deep floor above confined water is established. Through installing stress sensors and displacement-monitoring spots at different depths of the floor, the stress and displacement variation characteristics of floor rock mass during mining are obtained, and the development and evolution patterns of floor mining cracks are deduced. This research shows that the mining-induced cracks of the deep floor rock mass are mainly produced in three parts: open-off cut, the middle of the goaf, and the actual mining face; the crack types mainly include vertical tensile cracks, shear cracks, and layer cracks, and some small cracks have developed near the main cracks; in the process of mining, the mining-induced cracks evolve and penetrate through each other along the direction of the principle stress, and finally the water inrush channel is formed. In an actual coal seam mining process, it is necessary to monitor the crack state of these three parts of the rock mass and the pressure variation of the confined water. The research results can provide new guidelines for the management of deep water inrush disasters and the mining safety of coal resources. [ABSTRACT FROM AUTHOR]

The monitoring system of rock mass stability was established based on the microseismic monitoring technology in view of the problem that the dynamic disaster of ground pressure was easy to occur in the process of deep mining. The design of the monitoring network was optimized, and the wave velocity was corrected by the method of fixed-point blasting. A monitoring network with a positioning error of 10 m and a sensitivity of-- 2. 2 was established finally. The waveform of the monitoring data was picked up and the temporal-spatial evolution characteristics of microseismic events were analyzed) the potential dangerous areas were delineated) and the deformation and damage of the surrounding rock in the potential dangerous areas were analyzed. Finally the early warning precursor of dynamic disaster was summarized, which is that the microseismic events increased greatly and in a high level) the spatial distribution was concentrated highly, the energy index suddenly dropped and the cumulative apparent volume increased rapidly. The research results can provide a reference for the stability investigation of deep mining rock mass. [ABSTRACT FROM AUTHOR]

Copyright of Forensic Science & Technology is the property of Institute of Forensic Science, Ministry of Public Security and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To study the oxidation characteristics and spontaneous combustion micro-evolution characteristics of coal unloaded under different initial stress, in this paper, a comparative study on the micro-oxidation characteristics of the raw coal samples with easy spontaneous combustion and the unloaded coal samples under different initial stress was carried out by using the temperature-programmed experiment, the three axial creep test of coal rock, and the mercury injection experiment. The findings indicate that in the macroscopic aspects, the unloaded coal under different initial stresses is easier to oxidize than the raw coal sample. The CO production–strain curve of the experimental coal samples is similar to the axial stress–strain curve; when the initial stress reaches 25 MPa, the coal sample is in the stage of strain softening and the oxidation capacity of coal sample is the strongest. The infrared spectra of FTIR are analyzed, and the dynamic changes characteristics of microactive groups such as aromatic hydrocarbons, aliphatic hydrocarbons, and oxygen-containing functional groups under different initial stress are mastered. The microscopic spontaneous combustion mechanism of unloading coal under different stress is obtained. [ABSTRACT FROM AUTHOR]

The process of fault activation and sliding induced by deep continuous mining is characterized by grey system. The GM (1, 1) grey prediction model is established based on the field measurement data of fault activation slip induced by deep mining in a copper mine. By comparing the predicted and measured slip values of faults, the model has high accuracy. The grey prediction model of fault activation slip is used to predict the future four phases of fault slip. The growth rate of F2 fault slip is fast, which is consistent with the actual situation in the field. The research results are of great significance to the prediction of active slip under the influence of complex deep mining. [ABSTRACT FROM AUTHOR]

Based on the analysis of rock structure changes by microscope, the adverse effects of groundwater on deep mining engineering are studied from the aspects of mining engineering joint fissures and deep mining surface subsidence. Sanshandao gold mine is a complex water filled mine mainly composed of fissured strata. Based on the field investigation of the joint fissures in the three depths of the mine, the distribution law of the joint fissures in the three depths of the upper wall, ore body and lower wall is analyzed. The integrity of the rock mass is successively reduced from the lower wall, ore body and upper wall. With the increasing mining depth, rock mass joints develop more and more intensively and rock mass stability becomes worse. It is easy to produce potential dangers such as mine gushing, water inrush and even seawater burst. The deep mining project of Sanshandao Gold Mine was completed by using three-dimensional finite difference method software FLAC3D. The numerical modeling and calculation of surface subsidence caused by groundwater were carried out. It was concluded that the surface movement angle along the direction of vertical orebody and along the direction of orebody caused by groundwater increased with the increase of mining depth and was easy to build. Geological disasters such as landslides and landslides in Chengdu mine destroy the ecological environment and affect the lives of residents and social stability. In view of the potential dangers of joint fissures and surface subsidence caused by groundwater in deep mining engineering of mines, the corresponding countermeasures are put forward, which have certain guidance and reference significance for ensuring the safety of deep mining engineering in complex hydrogeological conditions. [ABSTRACT FROM AUTHOR]

• Concentrated vertical stress steers high-stress strike-slip roadway instability. • The high-stress strike-slip unloading tri-zone is defined with the in-situ stress. • Establish a corresponding optimized borehole diameter-spacing design method. • Field tests were successfully carried out according to the research results. To effectively address instability and control failure caused by high roadway stress, this study focuses on the engineering context of the Jinfeng Gold Deposit in southwestern Guizhou. It simulates and analyzes the response of surrounding rock in high-stress roadways affected by strike-slip stress distribution (σ H ＞ σ v ＞ σ h) under varying drilling and pressure relief parameters, and conducts on-site experiments and monitoring. The study reveals that under strike-slip stress conditions when stress relief in the roadway's surrounding rock equals the initial vertical stress, the stress distribution maintains a 'bimodal' pattern. Establish an evaluation method for the stress range in the three-zone during pressure relief and the optimization of drill hole diameter-spacing design. The optimized drilling relief plan effectively shifts stress concentration, and the peak stress near the roadway decreases to the original rock stress level, with a 3.5 MPa reduction at the far end and a horizontal shift of 4.79 m with the unloading level (ε L) reaches 0.8375. Practical implementation confirms the effectiveness of the pressure relief design in unloading and transferring stress from the high-stress roadway's stress concentration area, achieving a 43.14 % deformation optimization on both sides of the roadway. These findings provide valuable references for controlling stress relief in high-stress roadways surrounding rock. [ABSTRACT FROM AUTHOR]

• 1 Stress distribution was recalculated by stress-softening and prominent dilatancy. • 2 Gas-bearing coal under impact loading was a compaction followed by ruin process. • 3 Measures principles were mainly aimed at fracture and stress-concentration areas. • 4 Preliminary goal-reaching parameter based on principles was proposed and applied. As the increasing demand for coal and the depletion of shallow coal resources, the tendency of coal mining in China is progressively shifting to deeper areas, which brings about a circumstance where the frequency and intensity of coal and gas outburst accidents have further deteriorated. Nowadays, there are many outburst prevention measures being applied on site, while this disaster still occurs from time to time. Therefore, to better improve the preventing outcome of them, this paper came forward with some principles, based on the mechanical theory of deep mining and damage evolution procedure concerning coal containing gas underneath the impact load. The primary conclusions were as follows: the stresses, strains, and associated widths in the three areas, namely fracture area, plastic area, and elastic area, in front of the working face were recalculated by considering stress-softening and dilatancy of coal mass. The damage evolution of gas-bearing coal mass under impact loading was displayed in the LS-DYNA numerical simulation as a process of compaction followed by destruction. The proposed principles could be split into two perspectives, one for the fracture area, specifically, to minimize the descending of the coal mass's strength in this area; another for the stress-concentration zone, namely, to abate the thrust due to extrusion and deformation, on the coal body which was located in the front area. According to those principles, a preliminary goal-reaching parameter was proposed and it was implemented for the evaluation of advanced drilling. The results will cooperate to rationalize the design and layout of local outburst prevention measures, thereby enhancing the efficiency of control and ameliorating the deteriorating scenario of outburst disasters. [ABSTRACT FROM AUTHOR]

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

An increased global supply of minerals is essential to meet the needs and expectations of a rapidly rising world population. This implies extraction from greater depths. Autonomous mining systems, developed through sustained R&D by equipment suppliers, reduce miner exposure to hostile work environments and increase safety. This places increased focus on “ground control” and on rock mechanics to define the depth to which minerals may be extracted economically. Although significant efforts have been made since the end of World War II to apply mechanics to mine design, there have been both technological and organizational obstacles. Rock in situ is a more complex engineering material than is typically encountered in most other engineering disciplines. Mining engineering has relied heavily on empirical procedures in design for thousands of years. These are no longer adequate to address the challenges of the 21st century, as mines venture to increasingly greater depths. The development of the synthetic rock mass (SRM) in 2008 provides researchers with the ability to analyze the deformational behavior of rock masses that are anisotropic and discontinuous—attributes that were described as the defining characteristics of in situ rock by Leopold Müller, the president and founder of the International Society for Rock Mechanics (ISRM), in 1966. Recent developments in the numerical modeling of large-scale mining operations (e.g., caving) using the SRM reveal unanticipated deformational behavior of the rock. The application of massive parallelization and cloud computational techniques offers major opportunities: for example, to assess uncertainties in numerical predictions; to establish the mechanics basis for the empirical rules now used in rock engineering and their validity for the prediction of rock mass behavior beyond current experience; and to use the discrete element method (DEM) in the optimization of deep mine design. For the first time, mining—and rock engineering—will have its own mechanics-based “laboratory.” This promises to be a major tool in future planning for effective mining at depth. The paper concludes with a discussion of an opportunity to demonstrate the application of DEM and SRM procedures as a laboratory, by back-analysis of mining methods used over the 80-year history of the Mount Lyell Copper Mine in Tasmania.

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.

To understand the resource features and geology in the deep Jinchuan nickel deposit, difficult geological conditions were systematically analyzed, including high stress, fragmentized ore rock, prevalent deformation, difficult tunnel support, complicated rock mechanics, and low mining recovery. An integrated technology package was built for safe, efficient, and continuous mining in a deep, massive, and complex nickel and cobalt mine. This was done by the invention of a large-area continuous mining method with honeycomb drives; the establishment of ground control theory and a technology package for high-stress and fragmented ore rock; and the development of a new type of backfilling cement material, along with a deep backfilling technology that comprises the pipeline transport of high-density slurry with coarse aggregates. In this way, good solutions to existing problems were found to permit the efficient exploitation and comprehensive utilization of the resources in the deep Jinchuan nickel mine. In addition, a technological demonstration in an underground mine was performed using the cemented undercut-and-fill mining method for stressful, fragmented, and rheological rock.

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.

Phage display technology is a common approach for discovery of therapeutic antibodies. Drug candidates are typically isolated in two steps: First, a pool of antibodies is enriched through consecutive rounds of selection on a target antigen, and then individual clones are characterized in a screening procedure. When whole cells are used as targets, as in phenotypic discovery, the output phage pool typically contains thousands of antibodies, binding, in theory, hundreds of different cell surface receptors. Clonal expansion throughout the phage display enrichment process is affected by multiple factors resulting in extremely complex output phage pools where a few antibodies are highly abundant and the majority is very rare. This is a huge challenge in the screening where only a fraction of the antibodies can be tested using a conventional binding analysis, identifying mainly the most abundant clones typically binding only one or a few targets. As the expected number of antibodies and specificities in the pool is much higher, complementing methods, to reach deeper into the pool, are required, called deep mining methods. In this study, four deep mining methods were evaluated: 1) isolation of rare sub-pools of specific antibodies through selection on recombinant proteins predicted to be expressed on the target cells, 2) isolation of a sub-pool enriched for antibodies of unknown specificities through depletion of the primary phage pool on recombinant proteins corresponding to receptors known to generate many binders, 3) isolation of a sub-pool enriched for antibodies through selection on cells blocked with antibodies dominating the primary phage pool, and 4) next-generation sequencing-based analysis of isolated antibody pools followed by antibody gene synthesis and production of rare but enriched clones. We demonstrate that antibodies binding new targets and epitopes, not discovered through screening alone, can be discovered using described deep mining methods. Overall, we demonstrate the complexity of phage pools generated through selection on cells and show that a combination of conventional screening and deep mining methods are needed to fully utilize such pools. Deep mining will be important in future phenotypic antibody drug discovery efforts to increase the diversity of identified antibodies and targets.

The existence of unexpected resources in the seas and oceans of the world and the real possibilities of covering of important part of the food and energy requirements of humanity in the context of the exhaustion, in a time not too distant, of the terrestrial resources have made that the interest for the world ocean grow steadily, currently, many entities within the European Union being involved in the activities of exploration and exploitation of the seas and oceans, both as technology providers and as mining operators because, despite its small size, this sector has the necessary potential to generate sustainable development and jobs for future generations. The European Union is becoming more and more interested in identifying viable technologies for commercial extraction of marine resources located at great depths, both in the areas located in the national jurisdiction and in the international area of the submarine territories and to participate in the elaboration of relevant regulations that take into account the requirements of the protection of the marine environment. In this context, this article aims to make a brief presentation of the international area of the submarine territories in the context of the European Union's interest in exploring and exploiting its resources. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aiming at the problem of floor failure in deep mining nowadays, taking a certain working face of a deep mine in Shandong, China as the engineering background, the method of numerical simulation and similar simulation are used to study the failure law of floor in the mining process. The numerical simulation results show that the vertical stress increasing area of deep mining is "bubble-shaped"; shearing stress is generally "butterfly-shaped"; plastic zone distribution is "rectangular-shaped", shearing failure is dominant in the surrounding and middle parts, the range of plastic zone decreases with the increase of the depth from the coal seam; when the working face is advanced to 100 m, the floor failure depth reaches 30 m and tends to be stable state no longer increase. The similar simulation results show that that with the increase of floor rock depth, the stress value decreases, and the stress propagation of floor rock mass to deep depth has a lag effect, and the lag time is longer with the increase of depth. Finally, the depth of floor failure in working face is measured by the method of subsection water injection in the downhole. The measured result shows that the maximum floor failure depth is 31.6 m, which is similar to the result of numerical simulation. The two results were verified each other. The numerical simulation can provide a reference for the study of floor failure law in similar mines, and it can also provide some guidance for the prevention and control of water inrush in deep mines. [ABSTRACT FROM AUTHOR]

High stress is the main feature of deep mining. The in situ stress plays a large part in rock fragmentation. In this study, an electric explosion system was developed to study the fragmentation behaviour of rock under high stress conditions. A series of test experiments, including electric blasting tests of copper wires in air and rock-like materials, and blasting crater tests under different stress loading conditions, were conducted. The dynamic evolution of the strain field, and crack propagation process during rock-like materials fragmentation were monitored by digital image correlation (DIC) technique. The results indicate: the electric explosion method is reliable and can provide a clean energy source for rock-like materials fragmentation. Besides, the static stress significantly affects the evolution of the strain field in specimens under electric explosion loading, and in turn changes the crack propagation behaviour, and the final shape and size of the fracture zone. Unlabelled Image • An electric explosion system for deep rock fragmentation is developed. • Evolution of strain field under combined static and electric explosion is analyzed. • Rock fragmentation process and mechanism under combined loading are revealed. [ABSTRACT FROM AUTHOR]

Coal and gas outburst disasters are prone to occur within rock cross‐cut coal uncovering in deep underground coal mines. To reduce the risk of coal and gas burst under rock cross‐cut coal uncovering, a technique of permeability enhancement using hydraulic fracturing sand‐carrying is proposed. Field test was conducted using HF sand‐carrying approach, and the effect of permeability enhancement was investigated. The results show that the evolution of cracks has been subjected three stages: energy slowly increasing and crack initiation, damage localization of coal seam and gradually failure, and crack instability expansion and formation of a complex fracture network system. In addition, it is found that "water‐sand" type injection of high‐pressure fluid carried sand into HF cracks, which creates a support force on crack surface and prevents crack closure. A fully developed fracture network system with high flow conductivity capacity is created and thus increases gas permeability largely. Furthermore, a clearly increasing trend associated with the HF sand‐carrying is found for the treated coal seam area. The permeability coefficient is about 21.5‐30.5 times higher than that from the raw coal seam. A good prevention effect of coal and gas outburst is achieved using HF sand‐carrying method. [ABSTRACT FROM AUTHOR]

Engineering disasters occur frequently and violently with the increase in mining depth, which is mostly due to insufficient study on the failure mechanism of the deep rock mass. In this paper, theoretical and experimental researches on the failure behaviors and deformation control of deep surrounding rock in recent years were reviewed. Macro/meso failure mechanism of deep rock or coal–rock combined body under different loading conditions have been systematically investigated. Stress gradient failure theory of surrounding rock, uniform strength support in the deep roadway, and the analogous hyperbola movement model of overlying strata were preliminary established and a combined grouting control technology for surface and underground was proposed. Abovementioned achievements are expected to offer theoretical bases and technical supports for the exploitation of China's deep mineral resources in the future. [ABSTRACT FROM AUTHOR]

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The paper introduces the important influence of the law of ground pressure on the deep mining of the mine. Through the application of FLAC3D software to numerical simulation calculation of two working conditions in the mining process of a copper mine 59# ore body, it is found that when the 59# ore body is mined to the middle of the 15th section, the disturbance to the surrounding rock is small, and there will be no large-scale collapse of the roof. Mining has the greatest impact on the stability of the 3# goaf, and has the least impact on the stability of the 2# goaf. The stability of the empty area has a certain effect, but the effect is not great. With the increasing mining depth of the 59# ore body, its influence on the fault is gradually increasing, while the waste rock filling has little effect on the stability of the fault. It is concluded that as the mining depth increases, the disturbance to the surrounding rock becomes more and more serious, the stability of the surrounding rock decreases, and the possibility of sudden roof caving is greater. Once the roof caving suddenly occurs, there will be greater noise and vibration in the underground. However, due to the caving mining method adopted in this copper mine, there are a lot of caving overburden and roof in the upper part of the stope. Sudden falling will not cause rock burst. [ABSTRACT FROM AUTHOR]

With the development of deep mining, the mining pressure on the working face is increasing, the failure height of thick seam roof is increasing, and the failure characteristics of roof are becoming more complex. The cracks in the overlying strata of the roof are greatly increased and activated by mining influence, which increases the impervious threat of the roof. In order to solve this problem, the failure stress model of thick coal seam roof was established; the 1308 working face of Yancheng Coal Mine was taken as the engineering background, and the FLAC3D numerical simulation software was used to simulate the formation failure process of 1308 working face with the threat of water permeability; the drilling section water injection test method was used to measure 1308 working face; High water material is used as raw material to fill 1308 working face. The results show that: (1) the failure height of overlying strata is calculated more accurately by mechanical model, and the failure characteristics are analyzed; (2) the failure height of overlying strata calculated by numerical simulation is smaller than that calculated by theory; (3) the problem of serious roof caving in thick coal seam can be effectively alleviated by filling with super-high water material. [ABSTRACT FROM AUTHOR]

Phage display technology is a common approach for discovery of therapeutic antibodies. Drug candidates are typically isolated in two steps: First, a pool of antibodies is enriched through consecutive rounds of selection on a target antigen, and then individual clones are characterized in a screening procedure. When whole cells are used as targets, as in phenotypic discovery, the output phage pool typically contains thousands of antibodies, binding, in theory, hundreds of different cell surface receptors. Clonal expansion throughout the phage display enrichment process is affected by multiple factors resulting in extremely complex output phage pools where a few antibodies are highly abundant and the majority is very rare. This is a huge challenge in the screening where only a fraction of the antibodies can be tested using a conventional binding analysis, identifying mainly the most abundant clones typically binding only one or a few targets. As the expected number of antibodies and specificities in the pool is much higher, complementing methods, to reach deeper into the pool, are required, called deep mining methods. In this study, four deep mining methods were evaluated: 1) isolation of rare sub-pools of specific antibodies through selection on recombinant proteins predicted to be expressed on the target cells, 2) isolation of a sub-pool enriched for antibodies of unknown specificities through depletion of the primary phage pool on recombinant proteins corresponding to receptors known to generate many binders, 3) isolation of a sub-pool enriched for antibodies through selection on cells blocked with antibodies dominating the primary phage pool, and 4) next-generation sequencing-based analysis of isolated antibody pools followed by antibody gene synthesis and production of rare but enriched clones. We demonstrate that antibodies binding new targets and epitopes, not discovered through screening alone, can be discovered using described deep mining methods. Overall, we demonstrate the complexity of phage pools generated through selection on cells and show that a combination of conventional screening and deep mining methods are needed to fully utilize such pools. Deep mining will be important in future phenotypic antibody drug discovery efforts to increase the diversity of identified antibodies and targets. [ABSTRACT FROM AUTHOR]

With the mining depth gradually increases, the coal mines in Hanxing mining area are facing an increasing serious problem of water inrush threat from the ordovician limestone caused by the activation of concealed structures under the influence of mining. In order to determine the water inrush condition and the key treatment areas of coal seam floor, the initial seepage conditions and seepage path expansion laws of high confined water with different concealed structural types under the conditions of large deep and high water pressure should be studied. Therefore, the generalized mechanics models were established from the coaction mechanism of mining disturbance, concealed structure, combination of confined water, based on the analysis of geological characteristics and water inrush of typical coal mines in Hanxing mining area. According to the generalized mechanics models, the cracking condition, seepage strength and water-crack expansion criterion expressed by the principal stresses were obtained by the theoretical analysis of fracture mechanics. Then a classical solution method of boundary loads propagation in semi-infinite elastic plates was applied to derivate the mathematical expressions of the vertical, horizontal and shear stresses of the concealed structural coal seam floor under the coupling of mining stress and confined water pressure. Based on the obtained stress components, the stress state equation was solved by the invariants of the stress tensor to obtain the principal stress expression in the above water-crack expansion criterion. Taking the geological and mining parameters of the typical water inrush mine area in Hanxing area as an example, the case study was carried out and the extended path of coal seam floor crack was calculated using the Matlab program. Furthermore, the RFPA numerical simulation software, which can effectively simulate rock rupture and make fracture extension process visual, was applied to analyze the mechanical behavior of floor with different types of concealed structure and reconstruct the evolution process of confined water seepage path. The results of theoretical calculation and numerical analysis showed that the local stress disturbance of the concealed structure affected the expansion direction of the seepage path, so that three types of coal seam floor respectively showed different seepage paths. For the intact type of coal seam floor, the seepage crack extended to the boundary of both sides of the goaf with a " positive eight-character" shape from ordovician confined water layer. For the coal seam floor with concealed collapsed column, the seepage crack extended to the boundary of both sides of the goaf with an " inverted eight-character" shape from the top interface of the collapsed column to the depth of 28 m. For the coal seam floor with concealed fault, the seepage crack extended along the opposite direction of the fault extension line and stopped at depth of 30 m. The floor water-bearing fracture and the mining fracture expanded to each other and finally formed a seepage channel from ordovician confined water layer to the coal mining face. The result of seepage crack extension law of coal floor with different types of concealed structure obtained by theoretical analysis and numerical simulation could be used for predicting the confined water inrush path and targeted treatment of ordovician limestone kaster water disaster, in combination with microseismic monitoring technology which real-timely and dynamically catch the precursor information on concealed structure activation. [ABSTRACT FROM AUTHOR]

To investigate the tensile strength and fracture properties of sedimentary rock buried at different depths in Shendong coal field,the acoustic emission( AE) parameters of sedimentary rock specimens at different depths in Shendong coal field were monitored by AE monitoring system during the Brazilian splitting experiment. The variation of tensile strength,model I fracture toughness and the ratio k( tensile strength with respect to fracture toughness) of rock specimens with respect to the buried depth was discussed. The damage evolution,failure features and precursory features of specimens were also analyzed. The results indicate that the tensile strength and the fracture toughness increase with the increase of the buried depth and have power function relationship to the buried depth.In general, the tensile strength and the fracture toughness of rocks buried depth above-300 m are lower than 0.5 MPa and 0.15 MPa·m1/2, while those buried depth deeper than-300 m are higher than 1.0 MPa and 0.15 MPa·m1/2,respectively.The ratio k also increases with the rise of the buried depth,and has a logarithmic function relationship with the depth.The k values of rocks with the buried depth over-300 m are 2-3. The k values are 3-6 for the rocks with the buried depth close to-400 m,while the k values are relatively discrete for the rocks with the buried depth deeper than-500 m.In addition,the failure modes were observed similarly existing in the tested specimens,tension-shear mixed failure is the dominant pattern.However, the shear failure occurs at different time for the specimens with the various buried depths.For example,the shear failure begins to appear in the post-peak stage for the rocks with the buried depth less than-300 m, while the shear failure appears in the pre-peak stage for the rocks with the buried depth larger than-300 m.The failure precursors of the tested rocks appear normally before the peak strength, except the difference of the triggered stress. The precursors of the specimens( except medium-coarse sandstone) with the depth less than-300 m appear at the stress reaching 70%-90% peak stress. For the specimens with the buried depth larger than-300 m,the precursors appear at the stress larger than 92% of the peak stress.This indicates that the warning time of the specimen failure decreases with the increase of the buried depths. [ABSTRACT FROM AUTHOR]

In view of the characteristics of outburst, hysteresis and strong disaster caused by floor water bursting in deep mining, scientific and reasonable water inrush risk evaluation in advance is an important means to prevent water inrush in deep mining. In this study, an improved fuzzy comprehensive evaluation system for the risk assessment of floor water inrush in deep mining was established, and an veracious and feasible system method was proposed to evaluate the water inrush risk of floor water in deep mining. The evaluation indices were divided into continuous variable indices, which were quantitatively graded according to floor water inrush risk and discrete variable indices, which were qualitatively graded by expert opinion. According to the characteristics of continuous variables and discrete variables, the triangular fuzzy function and Delphi method were used to calculate the membership degree, respectively, and the analytic hierarchy process was applied to analyze the weights. In order to test the accuracy of the evaluation system, Evaluation of six engineering practices were carried through with hydrogeological data of six mining faces in China. The results are consistent with the field-observed results, which shows that the approach is reasonable and feasible, providing a powerful tool for the risk assessment of floor water inrush in deep mining. [ABSTRACT FROM AUTHOR]

The creep mechanical parameters inaccuracy of surrounding rock under high in-situ stress have become the “bottleneck” problem on the theoretical analysis and numerical calculation, therefore, determining the reliable rock mass creep parameters is urgently needed to be solved in practical engineering. An intelligent back analysis method of rock mass creep parameters based on the displacement increment sensitivity analysis for large underground caverns under high in-situ stress is put forward in this paper. This method is to use the fractional order calculus creep constitutive model which can describe the failure characteristics of surrounding rock creep over time under the high ground stress. Taking the displacements of arch roof, arch shoulder and sidewall as characteristic indices, five creep parameters (instantaneous shear modulus, viscosity coefficient, viscoelastic shear modulus, Viscoelastic coefficient, β) under inversion are confirmed by sensitivity analysis. Displacement increment data were extracted following the principle of “great value” and “sensitivity”. Fitness function of displacement increment is established by determining the inversion creep parameters inputting the eight incremental displacement monitoring information from the main power house and main transformer chamber. The construction of different level combination of learning samples and training samples of each parameter by using uniform design method, parameters value is confirmed by adopting genetic algorithm-neural network searching in the global space. Finally the comparative analysis on displacement increment measured values and calculated values is conducted through grey correlation analysis method and posteriori difference method. The results from underground powerhouse of Jinping II hydropower station show that the surrounding rock mass creep parameters are accurate, validated and rational. It also provides a new method for parameters determination during the long-term stability evaluation of large cavern under high in-situ stress. [ABSTRACT FROM AUTHOR]

Deep rock mass exists in a kind of environment with high geostress, high temperature and high pressure. The influence of mining on it is complex than that on shallow rock. The strong disturbance to deep rock mass was analyzed systematically by combining the surrounding environment of deep rock mass and the disturbance characteristics of deep mining. Firstly, the cooperation between static and dynamic disturbance were examined. According to stress paths in deep mining, both the distribution of initial geostress state and that of disturbance stress state under different depth ranges were given, which reveals the complicated char-acteristics of stress paths in deep mining. Thereby a preliminary formula to calculate unloading velocity was proposed based on rock depth, mining method, rock gravity, residual stress and excavating speed. According to the type of dynamic disturbance and the law of stress wave propagation in deep mining, the characteristics of fluid pressure propagation in deep rock mass was pointed out. Thus it is inferred that the disturbance scope in deep rock mass is extended and the disturbance time is prolonged. Then the influence of disturbance was investigated according Disturbed State Concept (DSC). A disturbance function based on energy feature was defined by analyzing the energy storage, energy dissipation and energy release of deep rock mass, which would be adopted to build a unified constitutive model of deep rock mass based DSC. Such function can quantitatively describe the disturbance in deep rock mass. Lastly, the distribution of excavation disturbance zone in deep rock mass mining and the corresponding stress-strain state were described qualitatively. It is suggested to be divided into Initial Elastic Zone, Excavation Damaged Zone (EDZ) and Excavation Fracture Zone, where Excavation Damaged Zone is divided into Inner Damage Zone, Plastic Disturbed Zone, and Unloading Damage Zone. A formula was given to calculate the size of Excavation Damaged Zone. Each pa-rameter in the formula was explained and the influence on them were discussed. The study shows that the disturbance to rock mass in deep mining become more severe due to the high stress state of the deep rock mass and the complex multi-field coupling of multiphase environment, and thus the range of EDZ is increased significantly with more complex temporal and spatial evolution. The disturbance function based on DSC and the formula calculating EDZ size based on energy analysis can quantitatively describe the extent of disturbance in deep rock mass. They reflect the increase of disturbance stimulus in deep rock mass and the increase of disturbance effect in deep rock mass respectively. [ABSTRACT FROM AUTHOR]

In China, the shallow mineral resources of the earth have been gradually exhausted. There are lots of engineering disasters in deep mining when mining at 1 000-2 000 m depths due to the unknown mechanism in deep mining-induced stress field. At the Ji15-31030 mining face with an over-kilometer depth in Pingdingshan Coal Mine No. 12, the research was carried out to study the mining-induced stress evolution law with different mining speeds. The in-situ monitoring tests including bolt stress testing, borehole stress testing and fractures in borehole monitoring were also carried out to investigate the appearance law of mining-induced stress field. Results showed that the peak advanced abutment pressure increases alternately as the mining face advances and fluctuates around 85 MPa due to great depths when mining over 80 m. The stress concentration factor is 3. 3, which is higher than that at shallow mining face. Overlying strata forms “three-zones” consisting of the caving zone, cracked zone and bent zone. Meanwhile, the peak advanced abutment pressure increases as the mining speed increases gradually, and the distance between peak pressure position and mining face decreases correspondingly, and the longer the length of the rock formed by the main roof breaking is. Hydraulic support pressure increases periodically with mining face advances. The bolt stress increases first and then decreases due to stress redistribution and energy releasing under the influence of mining, which concludes that mining influenced range is about 85 m. Borehole stress increases in the mining influence range about 75 m from the mining face, and decreases slightly when entering the advanced abutment pressure reduction zone. Strong mining disturbance results in fractures developing continuously as mining face advances, and fractures develop into crisscross broken zone as developed upwards. [ABSTRACT FROM AUTHOR]