Ore Pass Research Articles

PRINCIPLE AND APPLICATION OF CONTROLLABLE GROUTING OF CEMENT-SODIUM SILICATE SLURRY IN LARGE LOOSE ROCK MASS DUE TO MINING CAVING

Loose rock mass is a kind of common rock mass structure in mining,tunnel,underground space and other projects. It has the characteristics of low strength and poor stability. Grouting reconstruction is one of the important technologies to enhance its integrity and strength in site. To meet the special needs of the plugging project of the main ore pass with large-scale collapse under the condition of full rocks in Hebei provincial Xingshan Iron Mine,the concept of the controllable grouting of cement-sodium silicate slurry in the large loose rock mass is adopted. Based on the experimental study of cement-sodium silicate slurry grouting in the large volume loose rock mass,the grouting process was divided into the following five stages. They are vertical dominant seepage with macrovoid,circumjacent seepage with macrovoid,superior seepage stone,splitting and seepage of the first layer and splitting and seepage of the nth layer. According to the spatiotemporal propagation of slurry,the controllable grouting problem was divided into the one-dimensional vertical dominant seepage of cement-sodium silicate slurry and the circumferential spatiotemporal diffusion of single-stage grouting. and the mechanism of its occurrence was revealed that there is an exponential function with base e between the diffusion distance and the time of the one-dimensional vertical dominant seepage of cement-silicate slurry in the loose rock mass. On the basis of the above experimental results,the technology of the controllable grouting of cement-silicate slurry in the loose rock mass was applied to the plugging project of the main ore pass fully filled with large-scale collapsed rocks in the Xingshan Iron Mine,and good engineering performance were achieved.

Research on the Influencing Factors and Prediction Model of Impact Airflow in the Process of Unloading of an Ore Pass Based on a Coupled Computational Fluid Dynamics and Discrete Element Method.

In this paper, a coupled computational fluid dynamics and discrete element method (CFD-DEM) is used to numerically simulate the energy transfer of the ore falling process and the change law of impact airflow velocity under different influencing factors. The results are as follows: the total drag force is an important factor that determines the impact airflow velocity. The greater the total drag force, the greater the impact airflow velocity. The impact airflow velocity increases with the increase of mass flow rate and discharge height and decreases with the increase of ore size, and it is found that the discharge height has the greatest impact on the impact airflow velocity, the ore size is the second, and the mass flow rate is the smallest. Therefore, in the allowable range of mine production, the discharge height should be appropriately reduced. The mathematical model of the impact airflow velocity is obtained by multivariate nonlinear regression on the experimental results of orthogonal experiments.

Применение численного и блочного геомеханического моделирования для определения параметров крепления камерных выработок большого сечения

The study is exemplified by complex workings of a main ore pass that include a variety of underground structures, usually with unique dimensions which depend on the function and size of the equipment placed. The technical solutions for the underground crushing plant and associated structures envisage construction of chambers with the height of up to 35 m and the width of up to 20 m at the depths exceeding 800-1000 m. Such conditions call for a closer attention to be paid to the mine support parameters, especially the bolting depth. A block geomechanical model was designed in the Micromine Mining Software for the rock mass of the new main ore pass. Geotechnical boreholes logs and results of physical and mechanical rock tests were used as the input data for the model. Four domains were identified in the block geomechanical model for subsequent numerical modelling. A 3D model of the stress-and-strain state of the rock mass was made using the CAE Fidesys software based on the Micromine wire-frame model of the main ore pass. The history of the rock mass incremental loading was reconstructed for correct simulation of its stress-and-strain state. Prior to the excavation, the rock mass is pre-stressed by the weight of the rock strata. The excavation phase was then simulated in the stepwise manner. An array of points with the values of maximum principal stresses was downloaded from the numerical model post-processing program and interpolated into the block geomechanical model to refine the SRF parameter of the Barton's Q rating. Based on the obtained Q values, the mine support parameters for chambers were determined using the Barton, Hutchinson and Potvin empirical methods.

Plugging and Its Stability Evaluation for the Ore Pass in the Nonempty Condition Based on Controllable Grouting of Cement-Sodium Silicate Grout

Aimed at the problem to plug the main ore pass with the large collapse at Xingshan Iron Mine, the viscosity-time test and the heap perfusion test of cement-silicate grout in a loose rock mass are carried out. The relationship between the vertical diffusion distance of cement-silicate grout and setting time of grout is studied, and research results are applied to the design of plugging engineering of the main ore pass in -330 m. Based on the numerical simulation of the plugging structure and the long-term stress monitoring of the cable sensors, the stability of the plugging structure itself and the control for the movement of shafts nearby are comprehensively evaluated. The test results show that for a specific loose rock mass, the vertical diffusion distance of cement-silicate grout in the loose rock mass is a power function of grout setting time. Based on the design concept to plug the main ore pass with the large collapse using artificially constructed “bite-bonded arch,” the plugging design and construction procedures are proposed. A numerical model and long-term monitoring of cable stress show that the plugging structure is stable and has an obvious effect on the control movement of abutment shafts.

Study on Parameters of a New Gas-Water Spray in Ore Pass Dedusting Based on Experiment and Numerical Simulation.

To solve the problem of ore unloading dust in ore pass crosscuts, the atomization characteristics of a new gas–water spray and the effect of the ore discharge airflow on the spray effect were studied by experiments, and the installation position of the spray nozzle in the crosscut was determined by numerical simulation. The results show that when the gas–water flow ratio is 100–150, the atomization effect is the best. In this situation, the droplet size can be less than 28 μm. The impact airflow induced by ore unloading has a great influence on the size of the spray droplets, and the dust-collecting ability of the spray is negatively correlated with the impinging airflow. The best location for the spray is 5 m away from the wellhead. At this position, the impact airflow is less than 1.5 m/s, which can ensure that the total dustfall rate of the gas–water spray is 67% and that of the respiratory dust is 34%.

Research on Control of Ore Pass Dust by Unloading Time Interval and Foam Control Technology.

To control the dust pollution caused by the unloading of a multilevel ore pass, numerical simulation and similar experiments were carried out to study the airflow and dust migration influenced by the unloading quantity and the continuous unloading at different time intervals in the ore pass. From this research, the following conclusions are drawn: when the first level of the ore pass is unloaded, the third and fourth levels are the main dust-producing positions, and the concentrations of dust in the breathing zone can reach 85 and 325 mg/m3, respectively. Increasing the unloading interval and reducing the total single unloading quantity can prevent the superposition of dust production. The foam dust removal technology can reduce the secondary dust generation caused by the backlash of the airflow in the ore pass, and the dust emission rate can reach 60% at the fourth level.

Digital surface modeling of an ore pass to reveal orientation of principal stresses and effect of rock fracturing

Digital surface modeling of an ore pass to reveal orientation of principal stresses and effect of rock fracturing

The visualization study of dust pollution generated during unloading of the multi-level in high ore pass based on CPFD software and similar experiments

In addition to dust pollution of the environment, during the unloading process of the multi-level high ore pass, it also causes problems such as ore pass wall wearing and noise pollution. The dust pollution is harmful to the health of employees, which captures people’s attention. To grasp the diffusion law of the unloading dust in the ore pass and reduce the amount of dust discharged, the computational particle fluid dynamics (CPFD) software and similarity experiments were used to study the dust generation and diffusion principle under different unloading conditions. According to the results of the numerical simulations and similarity experiments: when the unloading flow rate is 1.0 kg/s, the dust production and wind speed at the ore pass mouth is the largest, and the maximum wind speed is 2.64 times the dust diffusion speed. The amount of dust generated during the falling of the ore accounts for 78% of the total dust production, and the secondary dust production after the ore falls into the mine bunker accounts for 22%. In the first level unloading, the third and fourth level are the main dust-producing points; the overall wind speed at the main dust-producing point first increases and then decreases, with the increase of the unloading flow. The wind speed and dust generated by unloading are inversely proportional to the change of ore particle size and proportional to the change of unloading height. It is possible to control the dust pollution of the ore pass, to a certain extent, by controlling the unloading flow, reducing the unloading height and increasing the ore particle size.

Relationship of coefficient of restitution and damping coefficient of rock

When rock travels through an ore pass, it falls, hits other rock materials, and ore passes walls. It is essential to understand the material flow and rock particle interactions in an ore pass to avoid hang-ups and accidents involving rock flow. Part of that understanding is to comprehend how rock reacts when it collides with other particles and other materials. It is difficult to determine the coefficient of restitution and the damping coefficient experimentally simultaneously. The objective of this study was to investigate the relation between the two parameters and determine their correlation mathematically. While it is difficult to measure the damping coefficient of rocks in a laboratory directly, results showed that it could be determined mathematically using the coefficient of restitution. Thus, it facilitates the use of rock flow dynamics simulation programs. Furthermore, the analysis showed that the coefficient of restitution exponentially decayed as the damping coefficient increased.

Relationship of coefficient of restitution and damping coefficient of rock

When rock travels through an ore pass, it falls, hits other rock materials, and ore passes walls. It is essential to understand the material flow and rock particle interactions in an ore pass to avoid hang-ups and accidents involving rock flow. Part of that understanding is to comprehend how rock reacts when it collides with other particles and other materials. It is difficult to determine the coefficient of restitution and the damping coefficient experimentally simultaneously. The objective of this study was to investigate the relation between the two parameters and determine their correlation mathematically. While it is difficult to measure the damping coefficient of rocks in a laboratory directly, results showed that it could be determined mathematically using the coefficient of restitution. Thus, it facilitates the use of rock flow dynamics simulation programs. Furthermore, the analysis showed that the coefficient of restitution exponentially decayed as the damping coefficient increased.

Study of high-pressure air curtain and combined dedusting of gas water spray in multilevel ore pass based on CFD-DEM

In order to solve the problem of dust pollution caused by ore unloading in ore pass, this paper, taking Li Lou Mining as a case study, conducted the wind speed variation law in the fluid domain and the impact of the collision between the ore in the unloading process on the fluid to determine the key dust control point based on the CFD-DEM coupling software. By Fluent software, the air curtain dust-proof efficiency under the action of unloading airflow is analyzed, and the relationship between the dust-control wind speed and the impinging airflow is known. And an experimental model of gas water spray is established to analyze the effect of spray dust removal. By analyzing the impact airflow and dust migration caused by ore unloading and the effect of air curtain dust control through numerical simulation, it can be seen that when the ore discharging quantity Mo = 4000 kg, the dust production is mainly concentrated in the fourth middle section. By high-pressure air shield assisting dust removal, dust diffusion can be better controlled when the ratio of impact wind speed of ore pass wellhead (denoted as λ) to high-pressure air curtain wind speed (denoted as ζ) is at least 1:8. When the dust removal effect is optimal, the ratio δ of the water supply amount ql and the gas supply amount Qg is determined by the gas water spray dust control experimental platform.

A New Plugging Technology and Its Application for the Extensively Collapsed Ore Pass in the Non-Empty Condition

Aiming at some long ore passes with severe damages and extensive collapses, we describe an optimal measure to plug a local area of ore pass in order to maintain the capacity of continued use. This paper, taking a new plug for the extensively collapsed long ore pass in the non-empty condition as a breakthrough, builds a structure-plugging system for ore pass based on plug effect, suspension effect, arch effect, and span-reducing effect. Meanwhile, a key plugging technology has been integrated which includes a stability evaluation method of plugging structure, controlled technology of drilling with casing in the composite rock mass, and controllable grouting for inhomogeneous loose rock mass. According to this structure-plugging system and technology, a case has been successful for the main ore pass in the Xingshan Iron Mine in China, which has created a precedent in the world. The practice results show that using this technology to plug the extensively collapsed long ore pass has a series of advantages including of scientific design, strong safety, high efficiency, and low cost.

Impulse force reductions and their effects on WBV exposures in high impact shovel loading operations

When shovels load the dump trucks with over 100-ton passes under gravity dumping conditions, they will create a large impact force on the dump truck body which generates high frequency shock waves which expose the operators to whole body vibrations (WBV). The main cause of such truck vibrations is the large impact force due to the gravity dumping of large tonnage passes. Therefore a rigorous mathematical model has been developed for the impact force containing all the necessary factors upon which it depends. Latter, a thorough analysis shows that percentage reduction of 7.19%, 9.40%, 13.27%, 14.8%, 17.30% and 18.13% can be achieved by reducing the dumping distance to 6.33 m, 6.0 m, 5.5 m, 5.33 m, 5.0 m and 4.9 m, respectively, as compared to when the dumping distance was 7.33 m. Even more reduction in the magnitude of impact force can be observed if the shovel pass gets divided into more than two sub-passes. Therefore, these models can be used to figure out the number of sub-passes into which a single ore pass can be divided and/or the extent to which the dumping distance can be reduced which would reduce the impact force significantly enough to obtain safer yet economic operations.

The effects of orepass loss on loading, hauling, and dumping operations and production rates in a sublevel caving mine

Ore pass failure is a well-known problem for deep mines and the risk of losing an ore pass is associated with severe production disturbances. In the near future, one possible scenario in the Loussa ...

Void fill and support techniques to stabilize drift excavated through a transition zone mined by a TBM at the Stillwater mine

Stillwater Mining Company is the only U.S. producer of platinum group metals (PGMs) and the largest producer outside of South Africa and Russia. The company controls a considerable portion of the J-M reef and is currently developing the “Blitz Project,” which will provide a main haulage level, ore pass systems, backfill plants, and flow-through ventilation to increase production and ensure sustainable extraction of this critical strategic mineral. While driving two sub-parallel footwall laterals 8125m in length, one of the development drifts experienced a massive fall in a geologically disturbed area created by a mafic dike intrusion. Combinations of a void fill material (Tekseal), polyurethane injection, fore poling coupled with steel arches, and supplemental bolting allow safe and efficient advance through this geologically disturbed zone. This paper presents the details of this project.

Cohesion and suction induced hang-up in ore passes

This paper addresses the problem of hang-up in ore passes. A hang-up in a plane ore pass is analysed using the methods of discontinuous stress and velocity fields. The system consisting of broken ore material and a stiff ore pass wall is idealised as a plastic-rigid continuum satisfying the Mohr-Coulomb failure criterion and an associated flow rule. The influence of moisture in the ore, and its associated suction, is accounted for using the effective stress concept for unsaturated geomaterials. A simple failure mechanism consisting of three rigid blocks is assumed which is consistent with a bursting failure type and with the existence of a compressive arch underneath the hang-up section. Stress equilibrium and kinematic restrictions enable the derivation of simple algebraic expressions governing the stability of a hang-up. The separate influences of suction and cohesion are evident in the derived expressions. The paper then applies the derived expressions to a hang-up problem. Strength properties of an ore are determined experimentally using triaxial tests. The way water is retained in the ore is described using its fractal characteristics. It is shown how the ore pass size for hang-up instability is strongly dependant on moisture content and suction. An increase in suction increases the minimum ore pass dimension needed to avoid hang-up formation.

Alternative Process Flow for Underground Mining Operations: Analysis of Conceptual Transport Methods Using Discrete Event Simulation

As the near surface deposits are being mined out, underground mines will increasingly operate at greater depths. This will increase the challenges related to transporting materials from deeper levels to the surface. For many years, the ore and waste transportation from most deep underground mines has depended on some or all of the following: truck haulage, conveyor belts, shafts, rails, and ore pass systems. In sub-level caving, and where ore passes are used, trains operating on the main lower level transport the ore from ore passes to a crusher, for subsequent hoisting to the surface through the shaft system. In many mines, the use of the ore pass system has led to several problems related to the ore pass availability, causing production disturbances and incurred cost and time for ore pass rehabilitation. These production disturbances have an impact on the mining activities since they increase the operational costs, and lower the mine throughput. A continued dependency on rock mass transportation using ore passes will generate high capital costs for various supporting structures such as rail tracks, shaft extensions, and crushers for every new main level. This study was conducted at an existing underground mine and analyzed the transport of ore from loading areas at the lower levels up to the existing shaft points using trucks without employing ore passes. The results show that, when the costs of extending ore passes to lower levels become too great or ore passes cannot be used for production, haul trucks can be a feasible alternative method for transport of ore and waste up the ramp to the existing crusher located at the previous main level. The use of trucks will avoid installing infrastructure at the next main level and extending the ore passes to lower levels, hence reducing costs.

A new ore pass repair method based on cavity auto scanning laser system accurate detection technology

Due to the limitation of traditional detection technology, it is hard to obtain the real shape of ore pass. The models thus obtained are often distortion, and the treatments are often poorly targeted. Based on the accurate 3D point cloud data by using cavity auto scanning laser system, the paper puts forward a new ore pass repair method - the key points protecting shell method. The research established and analysed the 3D model of ore pass before and after damage by integrating cavity auto scanning laser system with the modelling and analysis software. Analysis results show that the method not only can restore the system function of the ore pass effectively, but also solve the problem of of recovered ore pass simultaneously. The implementation result shows that it is an efficient and feasible new treatment which breaks the conventional ideas.

Application of DFN–DEM modelling in addressing ground control issues at an underground mine

A field case study is presented of an underground Canadian mine reporting ore pass problems. The ore pass has significantly degraded where a fault zone was intercepted. A geotechnical site investigation identified four rock mass domains along the ore pass including a fault zone. This information was used to generate a discrete fracture network (DFN) model for the rock mass. A kinematic analysis revealed that structurally controlled failure was not the only failure mechanism for the ore pass. The DFN model was subsequently used to develop 2D synthetic rock masses of the four rock mass domains. This allowed investigation of the influence of impact-induced damage from the transiting material. The maximum impact-induced damage was recorded for the fault zone. The mine adopted the recommendation to install a grizzly at the ore pass collar and cable bolts around the degraded ore pass zone. The recommendations contributed to the structural integrity of the ore pass.

NUMERICAL MODELLING STABILITY ANALYSES OF HAULAGE DRIFT IN DEEP UNDERGROUND MINES

Mine haulage drifts are the arteries of a mine. They are used for the transportation of blasted orefrom the draw point to nearby ore pass or dumping point in deep underground mines. Thus, theymust be remained functional during their service life. Otherwise, their instability could lead toserious consequences such as injuries, delay of production and increased operational cost. Theobjective of this paper is to evaluate the performance stability of mine haulage drifts with respect tomining step adopting numerical modeling of analysis. A two-dimensional, elastoplastic, finitedifference code (FLAC 2D) is built for the purpose of this study. Haulage drift performance isevaluated using stability indicators and numerical modeling results are presented in termsdisplacement, stress and the extent of yield zones with espect to mining step.