Ore Pass Research Articles

Cumulative damage characteristics of rock samples under cyclic low energy inclined plane impact

The ore pass wall in underground mines is often damaged by the impact and wear caused by unloaded ores. Studying the mechanisms of rock damage and failure under different impact angles can provide technical insights for the design and maintenance of the ore passes. This study employed an inclined impact experimental device along with a drop hammer loading test machine to perform cyclic low-energy impact tests on sandstone samples at five different inclined plane angles. The porosity of the rock samples was measured using a nuclear magnetic resonance (NMR) detection system, which provided data on porosity, T2 spectrum distribution, and NMR images of the samples after different numbers of impacts at different slope angles. The results indicate that: (1) Under cyclic inclined plane impact loading, an increase in the inclination angle, leads to reduced damage to the rock sample. The rock sample impacted at a 45° inclined plane exhibited the most severe damage. Rock samples with large inclination angles are more prone to experience rupture fractures at the tip of the inclined plane, primarily due to shear-tensile failure. The porosity changes dramatically at initially slope angles, resulting in greater damage. (2) As the number of impacts increases, the porosity of the samples first decreases, then increases, and subsequently decreases again. This progression corresponds to the closure of large pores following the first impact, followed by the expansion of micropores into macropores after 5 impacts, ultimately leading to gradual degradation of the samples until failure. (3) As the number of impacts increases, new cracks form within the rock sample and small cracks expand. Despite an increase in the number of micropores, the macropores still exert a significant influence on the rock samples, with the macropore spectrum area accounting for over 95%.

Influence of ore-drawing port position on ore-rock flow characteristics in ore pass and lateral pressure on ore pass wall

The blockage and the deformation and failure of the ore pass walls constitute two major problems in applying the ore passes in mines. These problems, which affect the normal operation of mine production, have attracted widespread attention worldwide. The labeled-particle layers method based on numerical simulation was used to investigate the flow characteristics of the ore-rock bulk in the ore pass under different eccentric distances of the ore-drawing port center and ore pass centerline. Moreover, the overpressure coefficient and overpressure number are used to evaluate the degree of damage to the ore-pass wall. The results show that: (1) During the ore drawing process under different eccentricities, the flow patterns of the topmost labeled-particle layers in the ore pass are always in a “—” shaped distribution, and the other layers in the ore pass gradually transition from a “—” shape to a “U” shaped distribution, and then gradually to a “V” shape closer to the drawing funnel; (2) in the range of the ore-drawing funnel, the flow pattern of the ore-rock bulk gradually changes from an upright “V” shape to an italic “V” shape with increasing eccentricity and tip slants to the drawing port, and is less affected in the shaft; and (3) the dynamic lateral pressure caused by the ore-rock flow mainly acts on the lower part of the storage section. When the eccentricity is 0.5 m, the maximum overpressure coefficient and overpressure times are the smallest, leading to the lowest damage degree of the ore pass wall.

Investigating the efficacy of foam-based dust particle capture for dust elimination in ore pass unloading: A similar experimental study

Dust pollution arising from ore unloading poses significant concerns for occupational health. The foam-based dust particle capture presents a promising solution for dust suppression due to enhanced wettability, broader dust capture area, and stronger adhesion. This study designed a similar experiment platform to investigate how unloading conditions and foam parameters influence airflow dynamics and dust migration. The results indicate that airflow intensity and dust source are pivotal factors affecting dust concentration. Additionally, applying foam at the unloading port on the first level or the ore bin proves effective. Foam-dust interaction duration and airflow intensity are crucial determinants of dust suppression efficacy. Furthermore, the study reveals that the foam has a dual effect on dust control: while it efficiently captures dust particles to mitigate pollution, it can also disrupt airflow unfavorably. This research offers valuable insights into optimizing the spatial arrangement and quantitative application parameters of foam equipment.

Analysis of Raise Boring with Grouting as an Optimal Method for Ore Pass Construction in Incompetent Rock Mass—A Case Study

Analysis of Raise Boring with Grouting as an Optimal Method for Ore Pass Construction in Incompetent Rock Mass—A Case Study

Expert Elicitation for the Resilient Design and Optimisation of Ultra-long Ore Passes for Deep Mass Mining

Extension of ore pass length has become increasingly critical for optimising energy-efficient underground mining operations. Long and ultra-long ore passes, spanning from 300 to 700 m, can significantly improve the functionality and viability of underground mass mining operations though suboptimal performance has an extremely adverse impact on production. The public domain lacks substantial information regarding the primary engineering, geological, and geotechnical risks and challenges associated with the design, implementation, operation, and maintenance of such long ore passes. Therefore, the aggregation of past experiences and the insights of experts assume paramount significance. An innovative methodology is introduced to address this evident data deficiency and to establish comprehensive guidelines for the resilient design of such lengthy ore passes — combining gap analysis with expert elicitation techniques. This equips design engineers with the necessary tools to formulate and adapt strategies for assessing the numerous challenges and uncertainties that invariably accompany their projects. Expert elicitation techniques are summarised, and a gap analysis is conducted with subject matter experts, from various countries, collating their extensive ore pass design experience, to create a comprehensive list of effective parameters and key risks that must be considered. Quantitative analysis of the survey results enabled the identification and ranking of the numerous factors affecting the design, operation, and maintenance of long and ultra-long ore passes and highlights the complex technical challenges (substantial damage from rock particle impact, increased dynamic mining stresses leading to failure, air-blasts and back blasts, dust, preferential flow, turbulent and dynamic material flow) that are uncommon in shorter ore passes. Additionally, increasing length heightens the probability of intersecting weak rock or discontinuities, leading to a higher risk of structural failure and instabilities. Faulting, folding, and large-scale structures are also critical geological factors to be considered in the design of such structures. The key geotechnical factor is also the rock type surrounding the pass. Experts highlighted the lack of clear guidelines for decision-making, resilient design, and construction so this work suggests future investigations to determine the complex interaction between the effective parameters, using approaches like the rock engineering system, discovery of cascading hazards, and optimal controls.

Study on the Macro-Fine Mechanical Behavior of Ore Flow Based on the Discrete Element Method

The mechanical behavior associated with the flow of ore-rock bulk materials is an important factor leading to the instability and failure of the shaft wall of the ore storage section in ore passes. It is of great significance for accurately understanding the stability failure characteristics of the shaft wall in the ore storage section in the ore-drawing process to understand the flow characteristics and internal mechanical transfer mechanism of ore-rock bulk. The flow characteristics, contact compactness, stress distribution characteristics, and contact force probability distribution of the ore-rock bulk are analyzed by the discrete element method, which realizes the quantitative characterization of the damage degree of ore-rock flow and reveals the damage mechanism of the shaft wall in the storage section of the ore pass. The results show that (1) in the process of ore-rock particle flow in the ore pass storage section, the macroscopic flow pattern of ore-rock particles changes from a “—” shape to a “V” shape, and the friction between ore-rock particles, particles, and the ore-pass wall is an important reason for the change of the macroscopic flow pattern; (2) the probability distribution of contact force strength between the particles decreases exponentially in the whole ore-drawing process, in which the strong force chains play a major role in the stability of the bulk system; and (3) the overpressure frequency and overpressure coefficient could be used to quantitatively characterize the wall damage degree under the action of ore-rock flow. The dynamic lateral pressure fluctuates periodically in exponential form and decreases, and the dynamic load formed by the ore-rock flow mainly acts on the lower part of the ore storage section.

Research on Intelligent Supervision System of Ore Pass

To prevent safety accidents caused by mining vehicles and personnel entering the operation area by mistakes, it is necessary to reduce the risk of the ore pass. However, the underground space of the mine is narrow, and factors such as dust and noise during the unloading process endanger the health of the personnel on duty in the ore pass. As such, the target detection technology based on deep learning is introduced into the underground monitoring system. The underground surveillance video samples are collected to establish a dataset for Yolov3 algorithm to identify minecarts. Through optimizing the Yolov3 model training process and algorithm, and using the dual-camera collaborative discrimination method, the influence of brightness on the recognition results when the loaders or trucks lights are turned on can be overcome. Four types of minecarts can be accurately identified from the underground surveillance video. On the basis of mining car recognition, an intelligent access control system for mine shafts based on Jetson Nano’s embedded development is developed. The on-site operation results show that the average accuracy of target vehicle recognition is within the range of 95%-100%. The system continuously recognizes the mine car 5 times from the detection program and sends the opening and closing command to complete a 90 ° rotation, which takes only 3 seconds，effectively meeting the needs of the mine for ore pass control.

Characteristics of force chains in the flow of photoelastic particles under a barrier

The essence of particle flow is the microscale breaking and rebuilding of force chains. Therefore, it is essential to conduct research on force chains during the process of particle flow. This study focuses on particle flow during the ore drawing process, develops a photoelastic experimental system for physical ore drawing, studies the macroscopic change characteristics of force chains, analyzes the statistical properties of force chain intensity, length, quantity, and azimuth, and discusses the particle blockage phenomenon and its engineering application in ore drawing. The results show that the length of the strong force chains is mostly about five particles, with fewer numbers, and their direction is primarily concentrated between 60° and 120°. Weak force chains are abundant and distributed uniformly in all directions. In addition, based on the arching and blocking characteristics of particles, a novel sealing method for the ore pass is proposed. The research results deepen the understanding of granular material flow hazards and provide a valuable reference for similar engineering analyses.

Experimental study on the probabilities of kinked arches and kinked arch locations in ore passes under the influences of multiple factors

A smooth shaft production process is important to ensure the safe and efficient development of mineral resources. Due to the influence of ore rock and the mismatch between rock size and ore pass design, an arching phenomenon occurs frequently during actual ore pass release, stagnating production. Therefore, an ore pass release simulator with a freely variable ore pass angle and height is designed and used to conduct a four-factor, five-level orthogonal ore pass release experiment. An analysis is performed to determine the influence of four factors—ore particle size, ore moisture, ore pass inclination and slip height—on the probability of ore pass arching; from there, an ore pass arching probability equation is constructed and the characteristics of the ore pass arching location are clarified, effectively predicting the probability of ore pass arching and providing an effective basis for handling arching events within an applicable range. This analysis effectively predicts the probability of ore pass arch within the applicable range, and provides an effective basis for handling ore pass arch events.

Analyzing degradation of ore pass walls in Kiirunavaara mine using scanning data

Ore passes play a vital role in underground mining operations by facilitating the gravity-driven movement of ore from production levels to lower levels. Failure of the ore pass has serious consequences, including possible production disruptions and substantial financial investments in reconstruction or rehabilitation. Failure mechanisms are often associated with rock mass quality, stress conditions, and wear of the ore pass walls. This study investigated the degradation of ore pass walls using scanning data at LKAB’s Kiirunavaara mine in Sweden. Geotechnical information obtained from various sources aided in further understanding the ore passes’ conditions. The study revealed variations in the ore pass growth rates, highlighting potential stability concerns and the correlation between throughput and pass growth. The findings underscore the need for continuous monitoring and regular inspection to manage wall degradation. The paper proposes potential rehabilitation measures to ensure the stability and safety of ore passes in mining operations.

An Underground Mine Ore Pass System Optimization via Fuzzy 0–1 Linear Programming with Novel Torricelli–Simpson Ranking Function

In this work, we propose a 3D dynamic optimization model that enables the design of an underground mine ore pass system with uncertainties. Ore transportation costs and ore pass development costs are quantified by triangular fuzzy numbers. Transportation costs are treated as production costs, and they vary over the duration of mining operation, while development costs of ore passes are treated as an investment, and they are treated as constant. The developed model belongs to the class of fuzzy 0–1 linear programming models, where the fuzzy objective cost function achieves a minimum value, with respect to given set of techno-dynamic constraints. Searching for optimal value in the fuzzy environment is a hard task, and because of that, we developed a new ranking function which transforms the fuzzy optimization model into a crisp one. A triangular fuzzy number can be presented as a triangular graph G(V,E) composed of vertices and edges. The x-coordinate of the Torricelli point of a triangular graph presents the crisp value of a triangular fuzzy number. The use of this model lets us know the optimal number of ore passes, optimal location of ore passes, and optimal dynamic ore transportation plan.

Autonomous detection and loading of ore piles with load–haul–dump machines in Room & Pillar mines

AbstractAutomation of machines in underground mines is a topic with increasing interest, both for research and industrial applications. Autonomous load–haul–dump (LHD) machines need to load material successfully before dumping it into a crusher or an ore pass. The autonomous loading method must be robust to enable reliable operation of the LHD during long periods of time. In this work, a method to perform autonomous loading in Room & Pillar mines is presented. It is based on detecting all ore piles in real‐time, and then computing attack poses in each pile. Then, a positioning process is performed to get the machine in front of the selected ore pile, and an excavation algorithm is executed for loading until the bucket is filled. The proposed method is able to detect multiple ore piles, with different slopes and sizes, and to consider different possible trajectories for attacking and loading the most feasible pile. The method was tested in the Werra Potash Mine, under real operational conditions. The results show that the method can load about 80% of the material that an experienced operator can load. Also, the success rate of the autonomous loading process is very high, being able to load enough material in all trials, and performing successfully the full procedure in 88% of the cases. Thus, the proposed autonomous loading method is a suitable alternative to be used in Room & Pillar mines.

Life-of-mine optimization for integrated open stope development and production scheduling using a mixed-integer linear programming framework

ABSTRACT Extraction and development sequences must be scheduled strategically in order to maximize the life of mine. The complexities and computational difficulties associated with underground mine planning makes it challenging and open to further research. This paper presents a mathematical programming framework based on mixed-integer linear programming (MILP) formulation for integrated open stope development and production scheduling. Additionally, the MILP model incorporates backfilling, operational levels control, and stope extraction duration control during production scheduling. The MILP model generated a net present value of $244.7 M and determined the capital, ventilation, operational, and ore pass development schedules as well as mining and processing schedules for a gold project with 25 years mine life. A total of 2.48 Mt of material was extracted and processed out of 2.88 Mt mineralized material.

Discrete element approach to determining rock mass pressure on ore pass walls

A critical safety factor of ore pass walls is the correct evaluation of rock flow pressure on the walls at the design stage. This study uses the discrete element method to determine load of rock flow on the ore pass walls. This method is the most effective in modeling ore flow through a trapdoor. On the other hand, modeling of each discrete particle can create an illusion that the model automatically takes into account all typical phenomena of granular medium. From this point of view, the method of discrete elements can be discredited in practice. Therefore, it is necessary to describe the methodology of constructing and correcting the discrete element and finite element models of ore passes. At the first stage, the grain size distribution of rock flow is analyzed, and the representative sample volume is determined. At the second stage, the shear tests are performed at the particle–particle and particle–ore pass wall contacts. It is required to implement both tests as the difference between internal and external friction angles can be assumed to be the cause of bridging (a silo phenomenon). At the third stage, due to essentially different kinematics of shearing andconical pile formation, the calibration criterion is chosen to be the angle of repose. The fourth stage is the bridging modeling and comparison of the model data with the analytical results. This stage is only limited to the numerical modeling as there are yet no fully developed techniques to reconstruct bridging in ore passes on a laboratory scale. At the fifth stage, the numerical experiments on filling an ore pass and on ore outflow from it are carried out. The results are transferred to a finite element method program.

Dust dispersion law and high-pressure air curtain control technology of crossheading during the process of ore unloading

In order to solve the problem of dust pollution in the crossheading caused by ore pass unloading, this paper studied the dust diffusion rule in the crossheading by numerical simulation, established the prediction model of dust concentration in the crossheading, proposed the high-pressure air curtain to control the dust pollution in the crossheading, and determined the dust control parameters of the high-pressure air curtain. The results show that the dust diffusion velocity in the horizontal direction is higher than that in the vertical direction; Discharge height and ore size have a great influence on the mean dust concentration in the crossheading, under the allowable conditions of mine production, the discharge height should be reduced and the ore size should be increased as much as possible; The Sparrow Search Algorithm (SSA)-Extreme Learning Machine (ELM) model can better predict the mean dust concentration in the crossheading of the numerical simulation results of this paper; The inclination of high-pressure air curtain decreases with the increase of air supply angle under the action of impact airflow. When the air supply speed and angle of the high-pressure air curtain are 35 m/s and 30° respectively, the dust removal efficiency of each section in the crossheading can reach 87.3%.

Study on the control of high ore pass dust pollution by pre-injection foam dedusting technology in the ore bin.

The impact airflow generated by ore unloading in the chute raises the dust carried by the ore itself and the floating dust, and then, the dust raised enters the roadway with the airflow and pollutes the environment. In order to minimize the amount of dust entering the roadway and reduce the pollution of unloading dust, we conducted an experimental study of selection of best foam formula and pre-injection foam dust dedusting technology in ore bin. It was found that the optimal foaming formula was 1.0% sodium dodecyl benzene sulfonate (SDBS) + 0.5% sodium dodecyl sulfate (SDS) + (0.2 ~ 0.4%) sodium carboxymethyl cellulose CMC-Na and coconut oil monoethanolamide (CMEA) by the compound experiment using two evaluation criteria of initial foaming amount and foam defoaming rate. When the air pressure is 0.7MPa, the foaming rate of the foam generator is proportional to the gas and liquid flow rate and the best foaming gas and liquid flow ratio is 27.8. Under this circumstance, the foaming rate of the foaming formula is 500l/min. When the height of foam is controlled at 15cm, the effect of foam dust removal is the best. The dust emission rate from the foam to the fourth level can reach 60%, and the dust fall rate of the third level is 28%, which effectively reduces the dust production and relieves the pressure of the spray hole dust fall at the wellhead.

Comparison of Productivity When Running Filled, Near-Empty, or Flow-Through Orepass Using Discrete Event Simulation

Ore passes are often the main part of sublevel caving transportation systems, and they use gravity to move material to lower levels in the mine. During operations, the ore pass structures are exposed to the risk of stoppage and failure, leading to a long-term reduction in operational capacity and affecting productivity. The failed ore passes can be restored or rehabilitated, but the rehabilitation cost is normally high and the time to restore is usually long. To minimize disturbances and stoppage of the ore pass, alternative strategies should be considered. The appropriate design and operation of an ore pass is crucial. Therefore, this study compared running ore pass systems in a filled, near-empty, or flow-through manner using discrete event simulation. The aim was to compare the ore pass operational performance and impact on reaching the daily and 90-day production targets of 76.4 Ktonnes and 6.9 Mtonnes, respectively. The results showed that running the ore pass in flow-through mode, filled manner, and near-empty manner achieved 96%, 80%, and 81% of the production target, respectively. In mining operations where ore pass systems are used to transfer material, running them in a flow-through mode can ensure higher production and fewer hang-ups, as it lessens the chance of blocks arching over a chute throat and leads to less blasting.

Visualization and Assessment of Hang-Up Phenomena Using Vertical Transparent Ore-Pass Models

Limestone is one of the most important mineral resources, and it is only one mineral that can be fully supplied by domestic producers. Generally, a certain amount of ores is stored in the ore passes temporally after blasting excavation, and extraction is carried out from the bottom of the ore pass. However, the hang-up phenomena in the ore passes sometimes occurred and some cases are recently reported. Once the hang-up phenomena in the ore passes occur, it will cause serious problems. In this study, ore flow experiments in the vertical ore passes were conducted using ore pass models which was composed of transparent acrylic tubes, and the conditions of hang-ups were discussed. Since the ore passes were assembled with transparent tubes, it was also possible to observe the hang-up phenomenon directly. To discuss the effect of cross-sectional shapes of ore passes, two kinds of ore-passes, that is, circular and square shapes of cross-sections, are prepared. Using various sizes of ores, the relation between ore size and cross-sectional area was also discussed. It was found that the hang-up phenomenon almost did not occur when the ratio of ore pass size to the mean grain size of ores exceeds the value of 5. It was also found that the circular-shaped ore passes were a little preferable to avoid ore pass hang-ups compared with the square ore pass. The same procedure was applied to the mixed ores which two types of ores with different mean diameters are mixed. In this case, also, the results were almost the same as the results obtained by single-size ores. 3D-DEM analysis was also conducted, and the validity of the experiments was discussed.

Detecting rocks in challenging mining environments using convolutional neural networks and ellipses as an alternative to bounding boxes

The automation of heavy-duty machinery and vehicles used in underground mines is a growing tendency which requires addressing several challenges, such as the robust detection of rocks in the production areas of mines. For instance, human assistance must be requested when using autonomous LHD (Load-Haul-Dump) loaders in case rocks are too big to be loaded into the bucket. Also, in the case of autonomous rock breaking hammers, oversized rocks need to be identified and located, to then be broken in smaller sections. In this work, a novel approach called Rocky-CenterNet is proposed for detecting rocks. Unlike other object detectors, Rocky-CenterNet uses ellipses to enclose a rock’s bounds, enabling a better description of the shape of the rocks than the classical approach based on bounding boxes. The performance of Rocky-CenterNet is compared with the one of CenterNet and Mask R-CNN, which use bounding boxes and segmentation masks, respectively. The comparisons were performed on two datasets: the Hammer-Rocks dataset (introduced in this work) and the Scaled Front View dataset. The Hammer-Rocks dataset was captured in an underground ore pass, while a rock-breaking hammer was operating. This dataset includes challenging conditions such as the presence of dust in the air and occluded rocks. The metrics considered are related to the quality of the detections and the processing times involved. From the results, it is shown that ellipses provide a better approximation of the rocks shapes’ than bounding boxes. Moreover, when rocks are annotated using ellipses, Rocky-CenterNet offers the best performance while requiring shorter processing times than Mask-RCNN (4x faster). Thus, using ellipses to describe rocks is a reliable alternative. Both the datasets and the code are available for research purposes.

Empirical approach to ore pass geometry justification in Talnakh mines

Ore mining in the Talnakh and Oktyabrsky fields using stoping methods includes construction and support of many temporal and permanent ore passes for ore haulage by gravity, which is the commonly known effective and cost-saving technology. Despite all benefits, there are some geotechnical complexities. For instance, making ore passes with smaller diameter increases their stability, which allows using them in difficult ground conditions, on the one hand, and, on the other hand, this can lead to frequent ore flow arching phenomena in ore passes and, consequently, to the increase in efforts for their elimination. This paper presents summary recommendations for selecting the cross-section shape and dimension of an ore pass based on global practice. The approach to determining the ore pass diameter with regard to grain sizes and properties of ore flow is substantiated. A series of experiments for determining the physical and mechanical properties (cohesion and internal friction angle) of ore mixture with a given particle size distribution at various degrees of moisture is carried out. Considering the determined properties, the minimum diameter of an ore pass to provide ore flow without formation of cohesive and interlocking arches is calculated. It is found that at the ore pass diameter of 2.4 m and at the maximum lump ore size of 254 mm, the material with natural moisture flows freely without arching in the ore pass.