Pit Walls Research Articles

Разработка трудноизвлекаемых запасов угля мобильными горнодобывающими комплексами без постоянного присутствия людей в зоне ведения горных работ

Today, millions of tons of coil remain in the subsoil and are written off as losses. These include hard-to-recover reserves unfit for mining with traditional high-performance means of integrated mechanization. One of the all-purpose technical solutions to the problem of developing such reserves can be technologies using robotic mobile mining equipment based on a heading-and-winning machine and a self-propelled car. Flowcharts for coal deposit development have been designed for seams unfit for mining with integrated mechanization means (medium thick seams, thick seams, flat and steeply inclined seams). These include open-pit and underground mining of marginal reserves from the side of the pit wall and limited reserves from the daytime surface performed by mobile mechanization means. During the operation of these means, the following process operations are repeated: coal breaking, loading into a self-propelled car, transportation along a preset trajectory, unloading into a reloader or other transport vehicle, or a warehouse on the bench. These operations can be robotized, which will increase both the safety and efficiency of coal mining. In order to perform coal-mining operations without constant attendance of maintenance staff, the existing mechanization means must be retrofitted with machine vision and a remote control system. Moreover, a robotized control system for the set of equipment must be developed to resolve the following problems. For the heading-and-winning machine: transportation (feed) along a straight line; transportation along the preset curve (formation of a diagonal entry); coal breaking at the preset thickness; coal breaking within coal-rock boundaries or along a preset cross-sectional contour; loading of broken coal into a self-propelled car; and control of the car loading level. For a self-propelled car: transportation along a preset trajectory from the loading point to the unloading point; control and management of the completeness of loading (unloading).

Energy control and block performance optimization of bench blasting

In this study, rock-like model blast tests with varying toe burdens are conducted and the evolution of blast-induced fractures is analyzed using the digital image correlation (DIC) method. In addition, post-blast fragmentations are image-processed to quantitatively investigate the blasting performance. A three-dimensional numerical model is developed and validated against the experimental results. The effects of blasthole inclination (70°, 80°, and 90°) and short delays on fragment size distribution (FSD) are numerically investigated. Field trials are conducted to verify the numerical results. The experimental results reveal that the overall fragment size increases significantly in proportion to the toe burden. The explosion energy utilization rates range from 3.56 % to 13.16 %, with a tendency to initially increase and subsequently decrease. The numerical results demonstrate that fragments are more evenly distributed with a blasthole inclination of 70°, resulting in a remarkable improvement in rock fragmentation compared to a vertical blasthole. Compared to the toe burden, the influence of short delays on concrete fragmentation is insignificant. The field test results indicate that a narrower FSD range and stable pit walls are achieved by utilizing inclined blastholes in bench blasting. This study provides theoretical guidance for optimizing bench blasting parameters, which has practical significance for improving explosive energy utilization and production efficiency in open-pit mines.

Numerical modelling of the pit wall stability while optimizing its boundaries to ensure the ore mining completeness

Purpose is to assess changes in the stress-strain state of walls along the whole periphery of a super-deep open pit while optimizing its current and final boundaries for the complete ore excavation. Methods. Finite element 3D analysis of stress-strain state (SSS) of the soil and rock mass relies upon the models varying in their scales. Macrolevel model includes the full pit helping perform initial evaluation of its stability depending upon changes in the general wall slope along the pit periphery. Then, the macromodel is separated into sectoral models with smaller scales oriented radially in such a way to include potentially unstable wall areas. The sectoral models make it possible to show the complex bench line in more detail after the peripheries were optimized in terms of economic factor and simulate layered structure of the rock mass. Elastoplastic model of the medium as well as Mohr-Coulomb strength criterion has been implemented using RS3 (Rocscience) program codes. Findings. An indicator of wall strength (safety factor) distribution along the pit periphery has been identified; potential sliding surfaces within each of the separated open pit sectors have been localized based upon the shear strength reduction (SSR) procedure. Influence by the general wall slope as well as by the indicator of the ore excavation completeness on the stripping ratio has been demonstrated. Originality. For the first time, two-level modelling has shown difference in a safety factor depending upon a model scale and a reflection degree of the soil-rock mass structure. In the context of the actual mining and geological conditions of Kacharsky open pit, changes in the safety factor along the pit periphery have been identified depending on the general slope of the wall. Practical implications. Based upon the pit wall stability along the whole periphery, the possibility has been substantiated to optimize its design boundaries for the excavation of those amenable ore reserves, occurred near them, inclusive of ore, occurring in a bottom, which mining is impossible due to inaccessibility.

Pit Slope Configuration for Open Pit Mining – A Case Study

To achieve stable pit wall slopes, it is imperative to obtain a fair knowledge of the rock mass characterisation before designing the pit. Insufficient knowledge of the competency of the country rock could lead to using unsupported slope configuration in the design process which can consequently lead to slope failure. In this study, the geomechnical properties of the Bremen-Nkosuo concession are analysed using Bieniawski’s classification scheme to determine the Rock Mass Rating (RMR) for defining safe pit slope configuration of the Nkosuo pit. The findings show that the rockmass are best described as ‘fair’ for the two main lithologies existing at the concession. Subsequently, localised adjustment factors are applied to the calculated RMR to arrive at Mining Rock Mass Ratings (MRMR). These MRMR values are correlated with 50 m fixed stack height and 1.2 safety factor to determine optimum Bench Slack Angle (BSA) of 54° and 57° for host sedimentary and granitic rocks respectively. For individual benches, optimum slope design configurations were 10 m, 800, and 6.6 m respectively for bench height, bench face angle and catch berm for metasedimentary rocks. Likewise, that for granitic formation were 10 m bench height, 800 face angle and 6.0 m catch berm width. These configurations are in conformance with mineral and mining regulations of Ghana. Slope stability assessment was performed which included Slope Mass Rating (SMR), Kinematic and Limit equilibrium analysis. From the analysis, multi-bench scale slope instability occurrence was found to be rare but single-double scale could be possible at the western wall of the planned pit with probability of failure of about 0.4. Presplit and trim shots perimeter blasting techniques are recommended to maintain the integrity of the final pit walls at certain areas.

Characteristics of Deformation and Stability of Ultra-Deep Pit in Plateau Alluvial–Lacustrine Gravel Strata

Deformation of ultra-deep pit walls and surrounding geotechnical bodies due to engineering disturbances typically shows intricate spatiotemporal patterns. In this study, deformations at critical steps of the construction process were first numerically simulated by Midas GTS NX, and this was followed by lab-scale geophysical model tests of the entire process of the pit construction. Data on deformation obtained from numerical simulations and lab-scale geophysical model tests were compared with those obtained from a dynamic monitoring scheme in the field to analyze the characteristics of the deformation and evolution of the pit wall. This was used to derive a generally applicable theoretical expression to predict variations in the horizontal displacements.

A few results of dynamics of inertial-impact machinery in pit wall slope trimming

A few results of dynamics of inertial-impact machinery in pit wall slope trimming

Slope stability analysis of an open pit mine with considering the weathering agent: Field, laboratory and numerical studies

Freezing-thawing (F-T) processes can affect the slope instability of open pit mine wall in cold regions, resulting the increase of mining operations cost and decrease the safety of personnel and equipment. Therefore, estimating the degradation of rockmass geomechanical properties under the weathering agent is crucial for slope stability analysis of an open pit mine in mountain areas. Accordingly, for optimal slope stability analysis of Angouran open-pit mine in this research, variations of physico-mechanical properties of pit wall schist rock including dry density, and uniaxial and triaxial compressive strengths were firstly measured during the defined F-T cycles. Then, the related properties of slope rock mass were determined using the generalized Hoek-Brown criterion. Based on the estimated rock mass characteristics, a numerical model of mine slope was constructed and pit stability conditions was analyzed. According to the obtained results, the displacement of slope rock mass varied from 0 to 14.6 m, occurred in highly weathered schist, indicating the low probability of large collapses. To validate the achieved results, 30 prisms were installed in the north-west wall of mine and in-situ displacements were recorded three times in week for one year. Results indicated that the measured displacements from in-situ monitoring and numerical model are in good agreement, so that the determination coefficient (R2) was obtained 0.80.

Evaluation of rock stability challenges affecting the formation of sustainable pit lake towards mine closure following crown pillar extraction in open pit-underground mines

The extraction of high-grade ore from the crown pillar (CP) in open pit-underground mines poses stability challenges and potential environmental risks. While an open pit has the potential to transition into a pit lake, the extraction of CP can induce failure in the surrounding walls, preventing the formation of the lake. There is also a concern that the backfilling material may not effectively confine toxic water within the pit, thereby risking contamination of the underground environment. To address these issues, a case study was conducted using FLAC3D and 3DEC models to evaluate the extent of failure caused by CP extraction. On-site observation, along with modelling, has revealed rock damage, including deformation stretching about 4 m from the pit wall and extending vertically from the pit floor to the ramp. The study identified three primary factors leading to pit wall failure or damage: steep pit slopes reaching approximately 70° near the pit floor, an underestimated CP thickness by about 4 m, and the concurrent extraction of ore from the pit wall alongside CP. Based on these findings, rehabilitation measures are suggested, including excavation of the deformed wall and cantilever, as well as partial pit backfilling. There is a substantial increase in the volume of backfill material as the extent of failure increases, which raise concerns about the decision-making process regarding CP extraction. Therefore, this article aims to raise environmental awareness and evaluate whether the benefits of ore extraction outweigh the considerations for pit wall support and the rehabilitation efforts during mine closure.

Causes of Pit Wall Failure in Zhelezny Mine by Radar Monitoring and Stability Calculations

Causes of Pit Wall Failure in Zhelezny Mine by Radar Monitoring and Stability Calculations

Sedimentation processes and morphological changes in a dredge pit and surrounding environment on Ship Shoal in the northern Gulf of Mexico

The use of dredged material from continental shelves and estuaries for degraded barrier islands has become a common practice worldwide. South Pelto block on eastern Ship Shoal (SS) off the coast of Louisiana has been dredged for high-quality sand resources, including Caminada Dredge Pit (CDP) and multiple pits in East Timbalier borrow areas (ET) adjacent to CDP. To understand how these dredge pits change and sediments infill over time, multiple surveys were conducted, including bathymetry, sidescan sonar, subbottom CHIRP, and sediment samples were collected for grain size analysis.Although there is no nearby muddy sediment, sidescan and grain size data both show low-reflectivity areas inside CDP became larger over time, indicating continual supply from suspended mud. Subbottom data show decreasing pit wall slopes over time and degassing over patchy low reflectivity areas on the pit bottom. Arc-chord rugosity analysis was performed with emphasis applied to ET to examine the difference between cutter and hopper dredge techniques. It was revealed that dredging from the hopper created a higher rugosity value than the cutter, leading to a shorter recovery time for the benthic environment. Bathymetric results reveal approximately 20 m to 60 m of horizontal outward pit wall migrations over 3–5 years. Hurricanes Marco, Zeta, and Ida as well as Tropical Storm Claudette passed the study site (within 50 Km) during the study period which increased wind-wave energies sufficiently to develop new sand ripples discovered on sidescan sonar data near ET and CDP. By integrating various datasets and investigating the effects of tropical cyclones on a dredged area in SS, this study contributes valuable insights that fill existing knowledge gaps and enhance decision-making for future management strategies.

Groundwater and surface water control at Highland Valley copper mine (HVC) (in rock and soil both)

This paper is about dewatering of the two large open pit porphyry copper-molybdenum mines of Highland Valley Copper in BC, Canada. These two pits occur within the well differentiated Guichon Creek Batholith with phases progressively more acidic and coarser grained towards the center and intersected by intense fracturing within the ore bodies and also concentric alteration haloes. Also, they are both cut by the steeply dipping Lornex fault which is an average 155 m wide faulting zone with frequent sympathetic faults adjacent to it. As the two pits have mined down at depth, they have exposed bedrock especially with frequent toppling-type faults and shears which have exhibited varying degrees of toppling and ravelling of the pit walls. Also, on the east wall of the Valley Copper pit, there is up to about 350m of glacio-fluvial overburden, originally with artesian flows in two or three aquifers. The toppling is exacerbated by the hydrostatic pressure of the groundwater in the pit walls. Both pits have significant groundwater and run-off in the spring. In order to be able to continue mining down to depths of about 600 to about 750 meters it has been necessary to de-water the walls and divert the surface run-offs to prevent infiltration into the toppling faults. So two water diversion projects were necessary at the crest of the highwalls and were completed to drain both by gravity and pumping the spring run-off water away from the two pits. Also, a major well drilling project is ongoing in the glacio-fluvial overburden aquifers to dewater them with upwards of 4500 US gpm flows. In addition, an annual series of horizontal drainholes were drilled and are ongoing approximately every three benches to dewater and depressurize the bedrock. Minor bedrock wells in the crest of the Lornex Pit also contribute to the dewatering. All the dewatering has allowed the two pits to mine down to close to design depths without significant disruption.

Organization of continuous monitoring of quarry sides

The article discusses the fundamental conceptual positions underlying the study of the significant impact of humanity on the lithosphere, which is approaching and may exceed its limits. It is noted that most surface layers of the Earth's crust are non-renewable, and the majority of chemical elements have found practical applications, yet only about oneseventh of the extracted minerals are used in the production of final products. One of the main challenges in developing open-pit mines is maintaining the stability of the pit walls. As the depth of the pit increases, this issue becomes increasingly critical. The article emphasizes the importance of enhanced study of the fundamentals of managing rock masses in mining operations and the practical application of this knowledge, as it significantly contributes to solving problems and examples related to assessing the stability of slope walls and pit benches.

Substantiation the safety open pit wall parameters in the conditions of a reduced protective zone near State critical infrastructure

The research is focused on topical issues of determining the safe parameters of pit edges in the conditions of a reduced protective zone near a critical infrastructure facility. Considering the extraction of soft rocks that are prone to landslides and deformations, the permissible safe distances from the upper edge of the pit on the surface to the industrial infrastructure facility are determined and established. Based on the physical and mechanical properties of the rocks, the parameters of geomechanical models of the pit edges were developed and substantiated to study their stability and stress state in the conditions of the Eastern section of the Chabanivske clay deposit. A brief description of the deposit under study and its geological structure is given. Computer modeling was carried out to determine the safety factor, and changes in the stress state of the massif near the pit edge were determined by the finite element method. Taking into account the mining technology were determined the safe parameters of the pit edges. Safe distances from high-pressure pipelines of state importance are substantiated. A rational pit edge angle of 28 – 31 degrees is recommended, and the appropriate safety distance for the rocks of the Chabanivske deposit in the western section should be at least 95 m.

Комплексный анализ результатов мониторинга устойчивости уступов карьера с использованием геофизических методов исследования

The Response to challenges related to safety in open-pit mining of mineral deposits is based on continuous monitoring of the pit wall stability as a whole as well as the stability of problematic areas of the pit wall and individual benches. Control of the geomechanical state of the adjacent rock mass using local geophysical methods plays an important role in the overall monitoring of stability of the open-pit elements. The control allows studying in more detail the state of benches and groups of benches in critical areas of the open-pit and developing measures to ensure production safety on this basis. One of the main interdependent factors affecting the pit wall stability is, on the one hand, the size of the disturbed zone that depends on both natural and mining-induced rock fracturing; on the other hand, the level of ground water changing over time depending on the season. The importance of joint account of the factors above has stipulated to propose a comprehensive methodical approach to study water saturation and structural disturbance of rocks in the wall of a deep open-pit. The method consists in periodic, seasonally synchronized, geophysical studies using seismic profiling and GPR sounding and allows identifying the areas of high water saturation and disturbance in the adjacent rock mass. The methodological approach makes it possible to estimate the effect of the main time-varying impact factors (water saturation, natural and mining-induced disturbance, anomalies of physical properties of the rock mass) on the slope stability and provides a scientific and technical basis for developing engineering measures to improve the safety of deep open-pit mining.

Численное моделирование процессов естественного проветривания карьера при вариации его глубины в условиях инверсионного состояния атмосферы

The research objective is to assess the influence of the background stratification parameter and the depth of an open pit mine on the time of natural ventilation of the mine and the level of atmospheric pollution at the upper side of the pit downwind of blasting operations in conditions of the North. An aerothermodynamic model of the atmosphere was used, in which the equations of dynamics in the approximation of incompressible fluid were supplemented with the heat transfer equation, and the buoyancy and background stratification mechanisms were taken into account. The model was created in a general-purpose COMSOL software package and makes it possible to study aerothermogasodynamics of the atmosphere in its various states. A two-dimensional CFD-model of the open pit atmosphere was tested using the recirculation ventilation process. The background stratification parameter (from 0.0 to +0.025 °С/m with the increment of 0.005 °С/m) and the quarry depth from 300 to 700 m were variated. The wind velocity of 1 m/s at the upper side of the pit, the initial location of the dust and gas cloud (in the center of the pit near its floor) and the slope angle of the pit wall of 45° were recorded. A significant increase in the time of natural ventilation of the open pit is demonstrated at intensifying inversion of the atmosphere. Two formation types of the maximum pollution area with the increasing pit depth are predicted: (1) displacement from the center to the lee side of the pit at neutral stratification; and (2) position in the center of the pit near its floor at positive background stratification. It is shown that increasing of both the pit depth and the background stratification parameter leads to a noticeable increase in the time to reach the maximum concentration at the upper side of the pit and a decrease in the value of this maximum. For the recirculation ventilation scheme, intensification of inversion in the atmosphere increases the time of natural ventilation, but reduces the level of atmospheric contamination at the upper side of the pit downstream.

Прогнозная оценка устойчивости борта карьера в тектонически напряженном массиве

The article presents an approach to determining the stability of the pit walls and benches using a set of methods. The results of numerical modeling of the stress-and-strain state are presented for the rock mass in vicinities of one of the quarries in the Khibiny Apatite Arc. Calculations were made using elastic approach to a three-dimensional finite-element model which incorporates basic geological, mining engineering and geomechanical data. The impact of gravitational and tectonic stress field is demonstrated on the stability of the pit wall and benches during its development. Potentially unstable areas have been determined in the wall and benches of the open pit design contour. The identified features of the stress-and-strain state of the rock mass in vicinities of the pit wall make it possible to increase the justification level of technical solutions for the development of surface mining operations and to design preventive measures that would ensure the stability of structural elements of the open pit.

TIME SERIES INSAR ANALYSIS FOR SLOPE STABILITY MONITORING USING SENTINEL-1 IN OPEN PIT MINING

Abstract. Surface mining is an important economic activity in many regions where mineral resources are located close to the surface. The process of ore extraction is characterised by high pit walls with steep slopes. The mining process introduces significant stress and strain changes that could lead to movement on the slope face. Slope failure on the pit walls can occur without warning and can lead to loss of life and disruptions to the mining process. The monitoring of slopes remains the most reliable way to detect movement on unstable slopes. Therefore, slope monitoring programmes have been established to monitor and measure slope movement to help mine management with the stability status of open pit slopes. Conventional monitoring techniques include visual inspections and in situ instrumentation that are point-based, time-consuming, and costly. Open-source remote sensing techniques such as Synthetic Aperture Radar interferometry have been used to monitor slope movements on open-pit mine walls. Time series interferometric Synthetic Aperture Radar (InSAR) can be used to overcome limitations of in-situ monitoring for monitoring slope movements in open-pit mines.

Development of a handheld integrating sphere snow grain sizer (HISSGraS)

Abstract We developed a Handheld Integrating Sphere Snow Grain Sizer (HISSGraS) for field use to measure the specific surface area (SSA) of snow. In addition to snow samples, HISSGraS can directly measure snow surfaces and snow pit walls. The basic measurement principle is the same as that of the IceCube SSA instrument. The retrieval algorithm for SSA from reflectance employs two conversion equations formulated using spherical and nonspherical grain shape models. We observed SSAs using HISSGraS, IceCube and the gas adsorption method in a snowfield in Hokkaido, Japan. Intercomparison of the results confirmed that with HISSGraS direct measurement, SSA profile observations can be completed in just ~1/10 the time required for measurement of snow samples. Our results also suggest that HISSGraS and IceCube have similar accuracy when the same snow samples are measured using the same grain shape model. However, SSAs of near-surface snow layers measured using the three techniques exhibited some biases, possibly due to rapid snow metamorphism or melting during measurement and some technical issues with optical techniques. When excluding SSA data for the surface layer, which metamorphosed remarkably during measurement, IceCube- and HISSGraS-derived SSAs correlated strongly with those obtained by gas adsorption and HISSGraS accuracy is 21–34%.

Рекомендации по эксплуатации и улучшению качества содержания карьерных автодорог Олимпиадинского и Благодатного горно-обогатительных комбинатов

A systematic increase in the volume of the rock mass extracted at the pits of the Olympiadinsky and Blagodatny ore mining and processing plants significantly raises the requirements for the smooth operation of the mining vehicles and optimization of the transportation cost due to a steady and significant increase in annual production and the average haulage distances. Along with a significant design depth (765 m for the Vostochny quarry, the Olympiadinsky ore mining and processing plant), mining is carried out within a rather narrow ring-shaped working area, which leads to high concentration of mining activities and makes it difficult to manage the operation of all types of equipment, including the process vehicles, for which the project justifies the slope angle of the pit roads to be up to 100‰, which would ensure the reduction of pit wall spreading and the decrease in the stripping volumes. The above features create specific conditions for road maintenance and require justification of measures to enhance these activities, which is one of the ways to reduce the cost of the rock mass haulage (with account of a comprehensive analysis of the current conditions and generalization of the experimental work results). Based on the results of measurements and observations of the road condition during the year, an analysis of the actual condition of the roads at the Olympiadinsky and Blagodatny ore mining and processing plants was carried out and measures to improve them were proposed. Based on the analysis of the specific features in formation and operation of the roads at the quarries of the Olympiadinsky and Blagodatny ore mining and processing plants, the article systematizes the recommendations on the in-pit road construction and maintenance. The article describes a methodology of optimizing the design (thickness) of the road topping. The economic effect of improving the condition of the in-pit roads in accordance with the increased haulage volumes has been determined.

A preliminary study on the formation of acid mine drainage through rock geochemical test in the coal mining areas

Acid mine drainage (AMD) is the biggest issue occurring in every mining industry. Therefore, it is necessary to check the rock, particularly its potency to form acid mine drainage. PT X in Lahat, South Sumatra does not yet own a distribution model for the PAF and NAF rocks. Thus, this research was conducted to determine the distribution of PAF and NAF rocks as an initial potency for the formation of acid mine drainage. Six samples in the field were taken from the pit walls, in which these sample codes were A, B, C, D, E, and F, respectively. These samples were subjected to the static and kinetic tests in the laboratory. The static test showed that a sample with a potency to form acid was sample E, while the other five samples did not have any potency to form acid. Afterwards, kinetic tests were conducted with a daily cycle for 25 days. The result showed that the sample F had lower pH value, compared with the other five samples. Thus, based on this study, it can be concluded that the only sample having the potency to form acid was sample F, while the other samples, namely A, B, C, D, and E, respectively, did not have any potency to form acids.