Pit Slope Research Articles

Pengaruh Pengambilan Keputusan Lokasi Pertambangan Batu Bara terhadap Dampak Lingkungan

Selecting a mining location is a matter that is so important in determining the location of a coal mine that must be chosen by a mining company. Several factors or criteria must be considered in determining the location of a coal mine, including soil material content, determination of the UPS (Ultimate Pit Slope), size and maximum depth limitation at the end of the pit, operation, ladder/bench dimensions, geographical and geological conditions, road geometric conditions and drainage system selection depend on groundwater conditions and rainfall in the mine area. From an environmental point of view, coal mining has an impact on changing landscapes, decreasing soil fertility, threats to biodiversity, decreasing water and air quality, and environmental pollution. Once operational, mines and acid mine drainage also remain in the mining industry. Former coal mines can have positive and negative impacts on the environment related to water quality and quantity. The purpose of this study is to determine the effect of choosing a coal mining location on environmental impacts. The method used in this research is the previous research review method. In which the researcher's efforts to find comparisons, then become inspiration for further research. Then, previous research helps the researcher position the research and prove the originality of the research.
 Keywords Mining, coal, impact, environment

A geotechnical evaluation of the Cumba Pit Slope Failure, Dominican Republic

The combined availability of topographical, geological, structural, hydrogeological and monitoring data is rapidly increasing. Technology and software advances allow the real time incorporation of this data across various software platforms. This paper describes the back-analysis of a 70 m high, pit slope failure of an open pit gold mine in the Dominican Republic, using data from aerial photogrammetry, ground-based synthetic aperture radar and 3D limit equilibrium and finite element modelling. This back-analysis process is considered leading practice with the latest technology. The (northern) side of the Cumba pit slumped along a non-daylighting plane that was identified after the failure event. Remedial investigations included review of geological data, major structures, rock mass constitutive models and groundwater conditions. Topographical and structural data acquired from aerial photogrammetry, pre- and post-failure event, was input into 3D models to replicate observed ground movement. 3D models of pit progression were compared with displacements recorded by ground-based synthetic aperture radar to calibrate model inputs and increase reliability of forward predictions. Such a technical review was completed in less than one week, and the review process implemented for the Cumba pit slope failure now forms the baseline approach for all future geotechnical analysis at the operating mine.

Numerical modeling of open pit aeration under major blasts according to the dust factor

Research objective is to estimate the effect of major blast location, dust and gas cloud initial height, the wind current velocity at the upper pit slope on the time of pit aeration and on the level of atmospheric pollution of the upper pit slope downwind according to the dust factor. Methods of research. Aerodynamics and fine dust transport in 2D geometry was modeled in the COMSOL program. The aerodynamic characteristics were calculated using the incompressible fluid approximation with the standard (k–ε) turbulence model. The process of fine dust spreading is modeled by numerically calculating the convective-diffusion equation for pollutants transfer, considering the settling rate. Numerical experiments were performed under a fixed initial concentration of fine dust and varying velocity of the oncoming wind current for three locations of major blasts and six values of the dust and gas cloud initial height (from 70 to 420 m with a step of 70 m). Results and analysis. Significant qualitative (but not quantitative) similarity was noted in the calculated spatial-temporal parameters for fine dust and the gas component. It is shown that for the recirculation aeration scheme, the longest duration of pit cleaning from dust is observed during major blasts displaced to the weather pit slope. A wave-like removal is predicted of dust pollutants with different heights of peaks and time to reach the peak value. Differences are demonstrated in the processes of pit aeration during major blasts in terms of fine dust and gas component, which do not contradict the physics of the process. Conclusions and scope. A functional dependence has been obtained, which makes it possible to predict the time of reaching the first peak of dust pollution at the upper pit slope downstream as a function of two variables, namely, the initial height of the dust and gas cloud rise and the oncoming wind current velocity.

Hybrid Fiber Optic Cable for Strain Profiling and Crack Growth Measurement in Rock, Cement, and Brittle Installation Media.

Brillouin scattering-based distributed fiber optic sensing (DFOS) technologies such as Brillouin optical time domain reflectometry (BOTDR) and Brillouin optical time domain analysis (BOTDA) have broad applicability for the long term and real-time monitoring of large concrete structures, underground mine excavations, pit slopes, and deep subsurface wellbores. When installed in brittle media, however, the meter scale spatial resolution of the BOTDR/A technology prohibits the detection or measurement of highly localized deformations, such as those which form at or along cracks, faults, and other discontinuities. This work presents a novel hybrid fiber optic cable with the ability to self-anchor to any brittle installation media without the need for manual installation along fixed interval points. Laboratory scale testing demonstrates the ability of the hybrid fiber optic cable to measure strains across highly localized deformation zones in both tension and shear. In addition, results show the applicability of the developed technology for strain monitoring in high displacement environments. Linear relationships are proposed for use in estimating the displacement magnitude along discontinuities in brittle media from strain signals collected from the hybrid fiber optic cable. The hybrid fiber optic cable has broad potential applications, such as geomechanical monitoring in underground mines, surface pits, large civil infrastructure projects, and deep subsurface wellbores. The benefits of fiber optic sensing, such as the intrinsic safety of the sensors, the long sensing range, and real time capabilities make this a compelling technique for long term structural health monitoring (SHM) in a wide range of industrial and civil applications.

Substantiation of the optimal parameters of the bench elements and slopes of iron ore pits

Purpose. To establish the optimal parameters of the bench elements and slopes of the pit at the mining of Horishne-Plavnynske and Lavrykovske deposits of ferruginous quartzites for further use of these parameters at the design. Methodology. Methods for determining the influence of the bench height on the productive pit capacity involves taking into account the quality of the ore, the rate of the mining front advancement, the rate of pit depth at the mining operations, the total length of the mining front, as well as the angles of the working and non-working pit slops. Findings. The most effective parameters for mining benches and slopes of an iron ore pit are considered, using the example of the Ferrexpo Poltava Mining. Parameters of the bench elements with a height of 2430 m have been established, which are worked out in layers with a height of 12, 10 and 15 m. The studies carried out made it possible to establish that layers with a height of 10 m, followed by the final and temporary pit contour with a bench height of 30 m, can improve safety due to the flattened slope of the pit up to 45, while, with a bench height of 15 m, the angle of inclination of the slope will be 47. Originality. The established dependence of the pit ore productivity in percentage on the bench height suggests that with an increase in the bench (layer) height, the ore productivity of the pit decreases. Determination of the influence of the working bench (layer) height on the total volume of ore losses in the design contour of the pit makes it possible to assert that at constant angles of the bench slope and the ore deposit fall, the values of operating losses and clogging change in direct proportion to the height. Practical value. A technological scheme has been developed for the development of a bench with a height of 30m with a layer thickness of 10 m, which makes it possible to improve safety in the pit by pit slope flattening to 45, to reduce the cost of ore mining by optimizing drilling operations (shorter drilling time per well, reduction of overdrilling and etc.) and thereby improve the economic performance of the enterprise.

The Slope Safety, Heavy Metal Leaching, and Pollutant Diffusion Prediction Properties under the Influence of Unclassified Cemented Paste Backfill in an Open Pit.

Open-pit unclassified cemented paste backfilling (OPUCPB) methods have not only addressed the disposal problems of tailings but also eliminated geological hazards of high and steep open pit slopes and created conditions for ecological restoration of the open pit in the future. In this paper, slope safety simulations, heavy metal leaching, groundwater monitoring, and pollutant diffusion predictions were examined to evaluate the slope safety pattern and environmental protection enabled by OPUCPB. The results showed that: (1) The safety factor of the open pit slope was proportional to the height of OPUCPB operation. Under the condition of seismic force and seepage field, the safety factor of slope B was increased from 1.188 to 1.574 by OPUCPB. (2) The toxic and harmful components in tailings were significantly stabilized by the OPUCPB. Under the conditions of acid leaching and water leaching, the quality of the leaching solution met the requirements of the class III limit of groundwater (GB/T14848-2017). (3) The monitoring results of groundwater quality around the open pit showed that the OPUCPB had no effect on groundwater, and the water quality met the requirements of the class III limit of groundwater (GB/T14848-2017). (4) Considering the diffusion prediction of pollutants and groundwater under extreme conditions, it was found that the pollution process is slow, and the shortest time required for pollutants to reach the standard limit is 232 d at a distance of 50 m from the leakage point. Therefore, the influence of OPUCPB can be controlled, and this method can achieve improved reclamation of open pits and safety treatment of tailings. It was worth popularizing and applying in mining enterprises.

The influence of selected weather conditions on the safety of slopes of post exploitation lignite pits filling with water

The article describes selected atmospheric factors that may affect the stability of the end slopes of lignite post mining pits during their filling with water. The main factors such as waves, the influence of the ice cover and the wind were characterized.

Importance of 3D analyses on static and seismic stability of jointed open-pit mine slopes

Most studies on open-pit mine stability have been performed in two-dimensional (2D) mode, which neglects the effect of the circular shape and thus the effect of third-direction boundary conditions. The aim of this work was to study the effect of the third dimension on static and dynamic stability analyses of pit slopes by comparing results from two- and three-dimensional (3D) numerical and limit equilibrium analyses. Geomechanical data from Choghart open-pit mine, located in the seismically active area of central Iran, were considered under a historical earthquake (M = 6.4). Kinematic analyses showed that two tectonic blocks of the mine – BL1 and BL2 – are susceptible to wedge and planar failures, respectively. The 2D and 3D static analyses showed that both blocks are stable, with higher safety factors (SFs) obtained using numerical 3D analyses. In the dynamic analyses, both 2D and 3D analyses showed wedge instability for BL1. However, for BL2, the 2D numerical analyses showed instability whereas the 3D numerical and pseudo-static analyses indicated block stability. The results revealed that the 3D SFs are generally 20–40% greater than those from 2D analyses. This can be explained by the consideration of the third-direction effect, verifying the importance of 3D analyses.

On the Freeze-Thaw Instability of an Open Pit Slope Using Three-Dimensional Laser Scanning and Numerical Simulation

In order to reveal the instability law of open pit mine slope in high-cold and high-altitude area. Firstly, the slope structural plane is scanned by three-dimensional (3D) laser scanning technology, and the point cloud data is obtained to realize the intelligent identification of rock mass structural plane. The geometric parameters of rock mass are counted, and the physical structure model is established. Then, we carry out freeze-thaw cyclic tests on granite to obtain the corresponding mechanical parameters. Finally, according to the obtained mechanical parameters, we use RS2 finite element software to calculate the shear strength of structural plane and joint by generalized Hoek-Brown criterion and Barton-Bandis criterion, respectively, establish the geomechanical model, and use the finite element strength reduction method to calculate the safety factor of slope and judge the instability of slope. The results show that the physical and mechanical properties of granite deteriorate with the increase of the freeze-thaw cycle. Under the action of the freeze-thaw cycle, the pore water in the rock mass freezes and forms frost heaving force. The expansion of volume leads to the further development of joint fissures. The strength of rock slope decreases gradually with the increase of freeze-thaw cycle times, and the safety factor of slope decreases continuously. It shows that repeated freeze and thaw alternation makes the stability of mine slope worse and worse. The research results are helpful to prevent the occurrence of slope disasters in advance and are of great significance to effectively and safely manage the stability of slope, the treatment of open pit, and environmental treatment.

Applied Research on Underpinning Technology for Protection of Structure Closed to Deep Excavation

Building structures are insecurity when it is closed to foundation pit, which likely to collapse or produce large deformation due to design or construction faults. Dead loads of structures applied on the top of pit slope and add the probability of circular sliding of slope. Underpinning technology can transfer loads to the deeper soil layer and deformation had been restrained effectively. With the development of foundation underpinning technique, more and more mini-pile should be drilled through the foundation inner or outer buildings structures. When the structures protected by underpinning method, the foundation pit supporting project can be designed more easily and flexibly. By one engineering example, underpinning technology and foundation pit supporting technology are combined and applied to protect the stability of structures near the pit. Using the united method, the loads of structures are transferred vertical and pressure on the top is reduced highly, active earth pressure is lower at the same time, so that the excavation stability can be achieved more easily. The engineering examples provide better technical references for similar projects.

Probabilistic slope stability assessment of laterite borrow pit using artificial neural network

ABSTRACT Assessment of slope stability of abandoned laterite borrow pits in residential areas is highly desirable as theconsequence of its failure could be fatal. This study applied artificial neuralnetwork (ANN) to conduct probabilistic slope stability assessments of theborrow pits. To determine the corresponding factor of safety (FOS), randomshear strength parameters, slope geometry, structure load on the slope andstructure distance from the slope crest were used as inputs infinite-difference numerical simulations. The FOS was combined with ANNtechniques to derive a mathematical model for predicting the failureprobability. The effects of variability of soil shear strength parameters andcross-correlation between the parameters on the probability of slope failurewere examined. Results showed that the performance level of the pit slopes washazardous. Variability in shear strength parameters significantly influencedthe slope stability, while negative correlation coefficients between theparameters reduced the probability of the slope failure.

Iron ore underground mining under the internal overburden dump at the PJSC “Northern GZK”

Deterioration of mining conditions at mining deposits by open pit methods (increased mining depths, reduced ore deposit thickness) leads to an increase in mining costs. In Ukraine, to reduce open pit mining costs, overburden is disposed in temporary internal dumps located directly in the open pit over the ore reserves. Reactivation of pit areas with the temporary internal overburden dump located on them results in a surge of mining operations and deterioration of technical and economic indicators. Increased energy consumption, a decrease in working site parameters, an increase in angles of open pit slopes and stripping lags lead to unprofitability of open pit mining. One of the solutions to the mentioned scientific and engineering problem involves combined mining of deposits by integrated open pit and underground mining operations. The combined open pit-underground mining method enables reducing mining costs and enhancing technical and economic indicators. The suggested schemes for opening reserves located under the internal overburden dump enhance technical and economic indicators of deposit mining through making the internal dump a permanent one. This allows further disposal of overburden into internal dumps. Implementation of scientific recommendations and technological solutions resulted from the research performed (exemplified by the deposit Hannivske, Ukraine) reduces the cost of ore by 1.33 USD/t. At the same time, the total cost of building an underground mine makes 16.4 M USD, which is 30% less than when applying traditional opening vertical shaft schemes.

Study on the Size and Occurrence Effects of Equivalent Elasticity Modulus of Orthogonal Random Jointed Rock Masses

Under the engineering background of a + 144-m mining platform on an open pit slope of Xinqiao Mining Corporation, the eigenvalue distribution function of joints was acquired based on the massive statistics of field joints. Next, an orthogonal random joint model was constructed using the Monte Carlo method based on the UDEC software platform. Subsequently, the representative elementary volume (REV) size and occurrence effects of the equivalent elasticity modulus of the orthogonal random jointed rock mass were explored through numerical experiments with lots of discrete elements. The results showed that the equivalent elasticity modulus of the orthogonal random jointed rock mass was of evident size effect, and the relationship between the mean equivalent elasticity modulus Eeq and the REV size of the rock mass followed the negative power function distribution. Before the model size reached the REV size, its Eeq was greatly discrete. Under different joint angles, both the standard deviation σf and coefficient of variation δ of the equivalent elasticity modulus of this model presented discrete distribution. As the model size reached the REV size, the mean equivalent elasticity modulus Eeq showed “two-high and one-low” morphological distribution. Eeq was small when the main joint angle was α∈[30°, 40°], but it was large when α = 0° or 90°. δ was taken as 10%, so the REV size of the corresponding Eeq was 10 m × 20 m. When the model size reaches the REV size, the occurrence effect of its equivalent elasticity modulus was no longer significant.

Stability prediction and optimal angle of high slope in open-pit mine based on two-dimension limit equilibrium method and three-dimension numerical simulation

The optimization design of the open pit slope can ensure safety in production at the same time bring considerable economic benefits, so it is necessary to evaluate the stability of the initial excavation scheme of the high slope in an open-pit mine and optimize the initial slope angle according to the evaluation results. In this paper, an exhaustive study of Anyi open-pit mine in mouding County Yunnan province China has been made, and the following results have been achieved: (1)Confirmed the geological factors which affected the slope stability of open-pit mine; (2)Quantified the stability of the open-pit mine slope; (3) Under the premise of safety, the angle of the open pit high slope has been optimized on the base of the calculations of the open-pit mine high slope stability so as to ensure the maximum economic benefit. In this paper, the study area was divided into six zones. Firstly, qualitative analysis of slope stability was made by analogy method of engineering geology and stereographic projection method according to the orebody location, the properties of rock and soil in slope, the height of slope, and so on. The analysis shows that the preliminary design of slope angle is so large to ensure safety. Secondly, the stability of different slopes of a high slope is the quantitative analysis of different zones in high slope was made by two-dimensional limit equilibrium method and the finite difference method. In this paper, the mechanical parameters of rock are obtained by a laboratory test, and the stability of the high slope is quantitatively analyzed by two-dimensional limit equilibrium and three-dimensional numerical simulation.

Geotechnical Issues in Decommissioning Surface Lignite Mines—The Case of Amyntaion Mine in Greece

Recent changes in the fossil-fuel energy sector require coal mining industries to plan for the future, including developing procedures for decommissioning and closure associated with mines. In surface coal mining, the geotechnical issues of decommissioning include the long-term stability of the pit slopes, particularly as the pit is gradually filled with water. This paper investigates such slope stability issues, with emphasis on the conditions prevailing in the Amyntaion surface lignite mine, in Western Macedonia, Greece. Analytical and numerical methods have been developed and used to estimate the temporal evolution of the overall safety factor, as the water level in the pit rises, creating a lake. It is shown that until the water level in the lake reaches a critical depth of approximately 15–35% of the final equilibrium condition, the safety factor against the overall slope instability decreases slightly (by about 3% in the case study, and up to 5–10% in other conditions) compared to its value at the end of exploitation. At higher lake levels, the safety factor increases significantly, as the beneficial effect of the lake water pressure acting on the slope overcomes the adverse effect of pore water pressure rise inside the slope. In typical mines, the critical water depth is achieved within a few years, since the surface area of the pit is smaller at deeper levels; thus, more favorable slope stability conditions are usually reinstated a few years after mine closure, while the small reduction in safety during the initial stages after closure is inconsequential. The paper investigates the parameters influencing the magnitude of the small reduction in the short-term safety factor and produces normalized graphs of the evolution of the safety factor as the lake water level rises. The results of the analyses can be used in preliminary closure studies of surface coal mines.

Analysis of Slip Failure Characteristics and Support Deformation Law of Structural Planes and Rock Foundation Pits with Developed Karst Caves

This paper establishes a numerical analysis model for the slope of a high-inclined angle stratified foundation pit using support methods including row piles, pile-anchor supports, and combined pile-bracing-anchor supports. The reliability of the analysis conclusion was verified by comparing the stress and deformation laws of the support structures on the bedding rock side and the toppling rock side in different schemes, in conjunction with the measured data from Sanhuan South Road Station of Xuzhou Metro Line 3. In addition, on the basis of summarizing the deformation characteristics of the support structures on the bedding rock side and the toppling rock side, the design concept of sectionalized support based on the spatial effect was proposed, and the advantages of the sectionalized support design were elaborated in combination with the numerical analysis results.

Mine Slope Stability Based on Fusion Technology of InSAR Monitoring and Numerical Simulation

In this paper, the slope of the open pit of Dahongshan iron ore mine in Yunnan is taken as the research object, the safety coefficient and settlement values of the slope under natural and rainfall conditions are derived by the finite element software Midas/GTS, and the surface settlement versus time is produced by fusing the InSAR monitoring results of the study area for a whole year to judge the stability of the open pit slope. The results show that the settlement and deformation areas shown by numerical simulation and InSAR monitoring results are consistent; the comparison between InSAR monitoring results and rainfall intensity shows that the cumulative value of slope settlement has a high correlation with heavy rainfall. The safety coefficients of the slopes of the open pit under natural conditions and rainfall conditions are 1.50 and 1.21, the cumulative value of settlement in InSAR monitoring data for one year is 18.4 mm, and no obvious large deformation area is found. The use of numerical simulation combined with InSAR monitoring can realize the analysis of the stability of the slope of the open pit mine.

Mechanism of molten KOH+NaOH etching of GaN revealed by the slopes of etch pits formed at threading dislocations

The etch pit method is used widely to reveal dislocations in GaN via a molten KOH+NaOH solution. To understand the pit formation mechanism better, we performed a statistical analysis of the three-dimensional pit geometry. Particular attention was focused on the slope of the pit facet that forms an angle θ with the {0001} plane. It was found that tanθ is linearly proportional to the apparent pit depth D for a given type of dislocation. Therefore, the slope of the linear fitting (SLF) of tanθ vs. D/t (t is the etch time) could be used to identify the dislocation type and was more reliable than using pit widths. Transmission electron microscopy was used to confirm the results. It is thought that the SLF reflects the configuration of atomic steps at the dislocation core. Our results imply that pit formation is governed by thermodynamic pit nucleation at the dislocation core, followed by kinematic facet development.

Comparing Shear Strength Dispersion Characteristics of the Triaxial and Direct Shear Methods for Undisturbed Dense Sand

Obtaining representative samples for laboratory shear strength testing forms the foundation of a successful geotechnical investigation program. The selection of suitable laboratory testing methods and the understanding of their limitations in the mining of a mineral sands deposit is discussed. The pit slopes will comprise of cohesionless sand and silty sand. The method of recovering undisturbed samples in a deep drilling program is outlined. The use of undisturbed samples increases confidence and reliability in probabilistic stability analysis. The effective friction angle values from 40 consolidated undrained triaxial and 46 direct shear tests are compared. The direct shear test results are 5% lower than the triaxial test results due to subhorizontal bedding. In addition, the coefficient of variation for the triaxial and direct shear friction angle results are 4.3% and 9% respectively, indicating a larger dispersion in the direct shear test results. The triaxial and direct shear datasets result in distinctly different outcomes for pit slope optimisation studies with substantial financial implications. Incorporating triaxial test data in a 35° pit slope stability assessment results in a 36% higher confidence level of achieving or exceeding a factor of safety of 1.3, relative to using the direct shear test data.

Reconstruction of the northwestern slope of the open pit South Mining District Majdanpek for the purpose of reconstruction the active landslide

The exploitation of copper ore in the Majdanpek Copper Mine takes place at the open pit South Mining District. The operation takes place in the complex conditions, and a special feature is that the capital infrastructure facilities: the state road M24, 35 kV transmission line and ri-verbed of the Mali Pek River are located in the northwestern contour of the open pit. Due to the occurrence of landslide in this part of the open pit, the continuity of the ore exploitation process in the mining system of excavation-processing was endangered, as well as the stability of infrastructure facilities. Reconstruction of the northwestern slope of the open pit will eliminate all existing and potential risks and create the conditions for functioning of the mine and town of Majdanpek.