Backfilling is a common practice in the mining industry and the backfilling performance plays a significant role in supporting the surrounding rock mass. To evaluate the backfilling performance, an experimental apparatus has been developed to understand how backfill affects the compressive strength of sandstone specimens in the laboratory. Pebbles were selected to model the backfill and divided into

To extract more in-depth information of acoustic emission (AE) signal-cloud in rock failure under triaxial compression, the spatial correlation of scattering AE events in a granite sample is effectively described by the cube-cluster model. First, the complete connection of the fracture network is regarded as a critical state. Then, according to the Hoshen-Kopelman (HK) algorithm, the real-time estimation

The significant differences between hard rocks (more brittle) and soft rocks (more ductile) may suggest the use of different failure criteria. A strength criterion for soft rocks that includes intermediate principal stress was proposed. The new criterion includes two independent parameters: the uniaxial compressive strength (σci), which can be obtained from common laboratory tests or indirectly estimated

High stress concentrations around underground excavations can result in significant damage to deep hard-rock mines. These conditions can be the result of stopping activities, blasting, seismicity, or other mining activities. Large anisotropic deformation and excavation closure, especially under high-stress conditions, are expected if the excavation is located in a foliated or thin-bedded rock mass

Cryogenic fracturing with liquid nitrogen (LN2) offers the benefits of reducing the water consumption and adverse environmental impacts induced by water-based fracturing, as well as potentially enhancing the fracture complexity. We performed a series of laboratory experiments to explore the key mechanisms governing the breakdown pressures of shale during cryogenic fracturing. In this study, cylindrical

Assessment of drillability of rocks is vital in the selection, operation, and performance evaluation of cutting tools used in various excavation machinery deployed in mining and tunneling. The commonly used rock drillability prediction methods, namely, drilling rate index (DRI) and Cerchar hardness index (CHI) have limitations in predicting the penetration rate due to differential wear of the cutting

Bulking characteristics of gangue are of great significance for the stability of goafs in mining overburden in the caving zones. In this paper, a particle discrete element method with clusters to represent gangue was adopted to explore the bulking coefficient time effect of the broken rock in the caving zone under three-dimensional triaxial compression condition. The phenomena of stress corrosion,

The “three shells” cooperative support technology was proposed herein according to both the large deformation of the rock surrounding large-section chambers in deep mines and the precarious stability of the support structures therein. The development range of the plastic zone in the surrounding rock was controlled by a stress shell to reduce the difficulty of controlling the surrounding rock. Additionally

Multiple-seam gas coproduction is a technology with potential to achieve economic targets. Physical experiments could replicate gas flow dynamics in two seams. In this study, numerical simulation was conducted based on physical experiments. Through calibration, the simulated results agreed with the experimental results. Three findings were obtained. First, the pressure distribution intrinsically depends

This research reviewed the mechanics and gas desorption properties of intact coal, and tested the crushing work ratios of different intact coals, and then, studied the stress conditions for the failure or crushing of intact coal and the gas demand for the pulverization of intact coal particles. When a real-life outburst case is examined, the required minimum stress for intact coal outburst is estimated

Improving the quality of equipment training for the Heavy Equipment Operators (HEO) is a critical task in improving safety and eliminating equipment-related injuries in mining. One of major responsibilities for the HEOs is proper machine inspection. Traditional miner safety training includes the use of hardcopy documents and video instructions. However, modern mobile and computer technology offers

Ground failure is a major contributor to fatalities in underground mines in the US. Underground coal mines in the Northern Appalachian have weak roof rock composed of shale, which is prone to failure under high horizontal stress. Understanding the relationship among strength, specimen size and rock petrographic parameters is essential for developing an effective ground control plan. Size effect studies

The stress and gas pressure in deep coal seams are very high, and instability and failure rapidly and intensely occur. It is important to study the infrared precursor characteristics of gas-bearing coal instability and failure. In this paper, a self-developed stress-gas coupling failure infrared experimental system was used to analyse the infrared radiation temperature (IRT) and infrared thermal image

During deep mining, the excavation disturbance stress path is the domination factor for the stability of the surrounding rock mass as well as the ground pressure. One of the important parameters of the stress path is the loading or unloading rate of the disturbed rock or coal, which depended on the mining rate. To achieve a well understanding of the mining rate and its effect on the coal behavior,

In this paper, the spatio-temporal variation and propagation direction of coal fire were studied in the Jharia Coalfield (JCF), India during 2006–2015 through satellite-based night-time land surface temperature (LST) imaging. The LST was retrieved from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) night-time thermal-infrared data by a robust split-window algorithm based on

The characteristics of rock instability precursors and the principal stress direction are very crucial for the prevention of geological disasters. This study investigated the qualitative relationship between rock instability precursors and principal stress direction through wave velocity in rock acoustic emission (AE) experiments. Results show that the wave velocity variation exhibits obvious anisotropic

Physical upgrading of graphite is typically achieved with many stages of grinding and flotation to produce a concentrate with approximately 95% carbon grade. An innovative grinding and column flotation process has been developed for efficient graphite upgrading to substantially simplify the process flowsheet and reduce operating costs. In this process, a high-pressure grinding roller (HPGR) and a stirred

Precisely understanding the dynamic mechanical properties and failure modes of rocks subjected to true triaxial stress state (σ1 > σ2 > σ3, where σ1, σ2, and σ3 are the major principal stress, intermediate principal stress, and minor principal stress, respectively) is essential to the safety of underground engineering. However, in the laboratory, it is difficult to maintain the constant true triaxial

In this study, to confirm the effect of confining pressure on dynamic mechanical behavior and failure modes of concrete, a split Hopkinson pressure bar dynamic loading device was utilized to perform dynamic compressive experiments under confined and unconfined conditions. The confining pressure was achieved by applying a lateral metal sleeve on the testing specimen which was loaded in the axial direction

Ameliorating the problem of low leaching efficiency, long leaching period, and high agent consumption should be studied to efficiently exploit ion-absorbed rare earth ore resources. In this study, the surfactant sodium dodecyl sulfate (SDS) is used to enhance the leaching effect of an ion-absorbed rare earth ore by ameliorating the seepage effect for the first time. The effects of surfactant concentration

This paper researched the enhanced flotation separation performance of ilmenite and titanaugite using the mixed collector benzhydroxamic acid/dodecylamine (BHA/DDA). The interface assembly mechanism was mainly investigated through in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy combined with the two-dimensional correlation spectroscopy (2D-COS) and X-ray photoelectron

Automatically formed roadway (AFR) by roof cutting with bolt grouting (RCBG) is a new deep coal mining technology. By using this technology, the broken roadway roof is strengthened, and roof cutting is applied to cut off stress transfer between the roadway and gob to ensure the collapse of the overlying strata. The roadway is automatically formed owing to the broken expansion characteristics of the

It is significant to research the impact resistance properties of hydraulic support due to its key support role in the fully mechanized mining face. However, it is difficult for the entire hydraulic support to implement the impact experiment underground and analyze the response characteristic. Therefore, a dynamic impact experiment for the entire hydraulic support was proposed in this paper, where

The discontinuous nature of rock cutting can easily cause unwanted vibrations in the structure of a surface miner. If these vibrations are not properly addressed, the related stress cycles can gradually damage the chassis resulting in fatigue failures. These events can seriously undermine the safety of operators and digging operations may be stopped for days, with an obvious economic impact. This work

The stability of cemented paste backfill (CPB) is threatened by dynamic disturbance, but the conventional low strain rate laboratory pressure test has difficulty achieving this research purpose. Therefore, a split Hopkinson pressure bar (SHPB) was utilized to investigate the high strain rate compressive behavior of CPB with dynamic loads of 0.4, 0.8, and 1.2 MPa. And the failure modes were determined

This study aims at proposing a reasonable roughness parameter that can reflect the peak shear strength (PSS) of rock joints. Firstly, the contribution of the asperities with different apparent dip angles to shear strength is studied. Then the shear strength of the entire joint asperities is derived. The results showed that the PSS of the entire joint asperities is proportional to a key parameter θτ

Gravity is the most important load source in mining and geotechnical engineering, which causes both the stress level and stress gradient inside geomaterials. Different from the stress level, the influence of gravity-induced stress gradient on the behaviour of the material is still unknown. An in-deep study on it will help to promote the understanding of material behaviour, especially for those cases

The coal strength and deformation properties are key factors affecting safe coal mining and high-efficiency coalbed methane (CBM) development. In this paper, reconstituted coal samples are chosen to investigate the weakening behavior of gas on coal strength, meanwhile, its effects on coal deformation are quantitatively evaluated. The results indicate that the weakening degree of gas on coal strength

A common and important task in mining industry is to estimate the settlement or final volume of the tailings or backfill associated with sedimentation and self-weight consolidation. Up to now however, most existing analytical solutions were developed by only considering the settlement induced by consolidation. In this paper, the process of shrinkage tests has been compared with those of sedimentation

The gasification kinetic modelling of two Victorian brown coal (Yallourn and Maddingley) chars and the validity for entrained flow gasification were investigated in this study. The study was conducted in a thermogravimetric analyzer (TGA) at 750–1100 ℃, 30%–90% CO2 concentration using different char particle sizes within 20–106 µm. It was found that random pore model and modified volumetric model are

The distribution of the various organic and inorganic constituents and their influences on the combustion of coal has been comprehensively studied. However, the combustion characteristics of pulverized coal depend not only on rank but also on the composition, distribution, and combination of the macerals. Unlike the proximate and ultimate analyses, determining the macerals in coal involves the use

Large and super-large section chamber groups in coal mines are frequently affected by dynamic loads resulting from production activities such as roadway driving and blasting. The stability of the surrounding rock is poor, and it is difficult to control. In this paper, a similar simulation test was used to study the deformation and evolution laws of the surrounding rock of a triangle-shaped chamber

A novel method of pellet calcification roasting-H2SO4 leaching was proposed to efficiently separate and extract vanadium (V) from vanadium-titanium (V-Ti) magnetite concentrates. The leaching rate of V is as high as 88.98%, while the leaching rate of impurity iron is only 1.79%. Moreover, the leached pellets can be used as raw materials for blast furnace ironmaking after secondary roasting. X-ray photoelectron

In this study, the tomography of dynamic stress coefficient (TDSC) was established based on a mechanical model of stress wave propagation in bedding planes and a mathematical model of the stress wave attenuation in rock masses. The reliability of the TDSC was verified by a linear bedding plane model and field monitoring. Generally, the TDSC in the dynamic stress propagation of bedding planes increases

Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines, but negative effects may occur as the fracturing fluids are absorbed into the coal seam. Gas wettability alteration (GWA) technology can be used as it can enhance the gas and water mobility during dewatering process as a result of capillary pressure change. However, there have been

To evaluate the coal burst proneness more precisely, a new energy criterion namely the residual elastic energy index was proposed. This study begins by performing the single-cyclic loading-unloading uniaxial compression tests with five pre-peak unloading stress levels to explore the energy storage characteristics of coal. Five types of coals from different mines were tested, and the instantaneous destruction

This paper presents the development and implementation of an innovative mixed integer programming based mathematical model for an open pit mining operation with Grade Engineering framework. Grade Engineering comprises a range of coarse-separation based pre-processing techniques that separate the desirable (i.e. high-grade) and undesirable (i.e. low-grade or uneconomic) materials and ensure the delivery

Rockburst is defined as a phenomenon with immediate dynamic instability under excavation unloading conditions of deep or high geostress areas. Inadequate knowledge and lack of characterizing information prevent engineers and experts from achieving appropriate prediction results related to the rockburst behaviour. In this study, a data set including 220 rockburst instances was collected for rockburst

Surface roughness plays a significant role in floatability of coal. In the present paper, coking coal surface was polished by three different sandpapers and the surface properties were characterized by contact angle and roughness measurements. The effect of surface roughness on floatability was investigated by adhesion force measurement system for measuring interaction forces between droplets/bubbles

Multiple seam interactions are a major source of ground instability in several U.S. coalfields. Empirical methods are well suited for this problem, because while the mechanics multiple seam interactions are very complex and poorly understood, many mining case histories are available for analysis. This study makes use of an updated database that includes 356 multiseam case histories, including 67 unsuccessful

This paper presents a novel approach to investigate the relations between drilling signals and bit wear condition in real world full-scale mining operations. This research addresses the increasing demand for automation in mining to increase the efficiency, safety, and ability to work in harsh environments. A crucial issue in fully autonomous unmanned drilling is to have a system to detect the bit wear

The hard roof difficult to collapse easily causes gas accumulation, which threatens the production safety of coal mine. Therefore, roof pre-cracking is required. Although blasting and hydraulic fracturing can also crack the roof, blasting can easily induce rock bursts, whereas hydraulic fracturing needs complex equipment. In contrast, soundless cracking demolition agents (SCDAs) with noise-free, dust-free

This paper presents the development of an innovative standing support for underground mines. The main feature of this standing support is its exterior container, a combination of polyvinyl chloride (PVC) with large rupture strain and fibre-reinforced polymer (FRP) with high strength-to-weight ratio. To demonstrate the advantages of this cementitious grout filled PVC-FRP tubular (PFT) standing support

The effective reinforcement of two or more overlying layers of mine openings in a single installation is usually done by coupling of two standard rock bolts mainly during the extraction of medium-thick coal seams. However, field observations show that the couplers of multiple bolts often degrade or break mostly at their connections. These types of failures can be avoided by strengthening the couplers

The filtration and dewatering of fine clean coal not only ensure industrial water recycle in coal washing plant, but also reduce the moisture of coal product in order to meet the requirements of combustion or coking industry. Fine clean coal is mainly composed by organic matter, and the property difference of different organic matter determines the filtration and dewatering behavior. In this investigation

The spatiotemporal analysis of seismic zones characterised by the scattering and accumulation of strain energy in the roof-rocks of the excavated longwall panel where inelastic or elastic deformations occurred during hard coal seam mining is discussed. The studied longwall panel was designed to utilize the effect of partial stress relaxation caused by the earlier extraction of the coal seams located

Coal and gas outburst is a violent disaster driven by released energy from gas desorption. The initial expansion energy of released gas (IEERG) is a new method to predict coal and gas outburst. In this paper, an instrument for IEERG measurement was developed. Compared with previous setups, the new one which is equipped with three convergent nozzles and quick-release mechanism gets improved in data

Blasting of rocks has intrinsic environmental impacts such as ground vibration, which can interfere with the safety of lives and property. Hence, accurate prediction of the environmental impacts of blasting is imperative as the empirical models are not accurate as evident in the literature. Therefore, there is need to consider some robust predictive models for accurate prediction results. Gene expression

Solid backfill mining (SBM) is a form of green mining, the core of which is to control and minimize the deformation and movement of strata above longwall coal mines. Establishing a mechanical model that can reliably describe roof deformation by considering the viscoelastic properties of waste gangue is important as it assists in improving mine designs and reducing the environmental impact on the surface

To explore the failure mechanism of roadway in layered soft rocks, a physical model with the physically finite elemental slab assemblage (PFESA) method was established. Infrared thermography and a video camera were employed to capture thermal responses and deformation. The model results showed that layered soft roadway suffered from large deformation. A three-dimensional distinct element code (3DEC)

Roof bolts such as rock bolts and cable bolts provide structural support in underground mines. Frequent assessment of these support structures is critical to maintain roof stability and minimise safety risks in underground environments. This study proposes a robust workflow to classify roof bolts in 3D point cloud data and to generate maps of roof bolt density and spacing. The workflow was evaluated

The flow of blasted ore during mining of moderately dipping medium-thick orebodies is a challenge. Selecting a suitable mining system for such ore bodies is difficult. This paper proposes a diamond layout sublevel open stoping system using fan blastholes with backfilling to mine such orebodies. To evaluate the performance of system the relationships between ore recovery and stope footwall dip angle

In this article an attempt to determine the influence of mining factors on the seismic activity during the longwall mining of the upper layer of coal seam no. 405/2 in one of the Polish hard coal mines in the Upper Silesian Coal Basin was conducted. Two longwall panels were mined in analogous geological conditions and based on the same mining system and technology. However, there was significant difference

A series of gas inrush events occurred during development at Grosvenor Mine resulting in exposure to elevated levels of methane at the production face. A total of 22 gas inrush events occurred, with between 15 and 130 m3 of methane released during each event. The presence of an undrained seam in the immediate floor, geotechnical characteristics of the floor, and the stress environment all contributed

The exploitation of the underground is currently undergoing a major transformation process. Besides mining, alternative ways of utilization are playing an increasingly important role. These alternative utilizations include the storage of gases, the disposal of radioactive wastes, and the implementation of geothermal storage facilities. In addition, more and more mining operations are being shut down

Researchers from the National Institute for Occupational Safety and Health (NIOSH) are developing a coal pillar rib rating (CPRR) technique to measure the integrity of coal ribs. The CPRR characterizes the rib composition and evaluates its impact on the inherent stability of the coal ribs. The CPRR utilizes four parameters: rib homogeneity, bedding condition, face cleat orientation with respect to

Accurately estimating load distributions and ground responses around underground openings play a significant role in the safety of the operations in underground mines. Adequately designing pillars and other support measures relies highly on the accurate assessment of the loads that will be carried by them, as well as the load-bearing capacities of the supports. There are various methods that can be

Longwall mining has existed in Utah for more than half a century. Much of this mining occurred at depths of cover that significantly exceed those encountered by most other US longwall operations. Deep cover causes high ground stress, which can combine with geology to create a coal burst hazard. Nearly every longwall mine operating within the Utah’s Book Cliffs coalfield has been affected by coal bursts

In the Kaiping Coal field, mining of five coal seams, located within 80 m in the Kailuan Group, #5, #7, #8, #9 and #12 coal seam, is difficult due to small interburden thickness, concentrated stress distributions, high coal seam metamorphism, and complex geological conditions. By using the ZTR12 geological penetration radar (GPR) survey combined with borehole observations, the overburden caving due