Stope Structure Research Articles

Dynamic stress characterization and instability risk identification using multisource acoustic signals in cut-and-fill stopes

The quantitative characterization of rock mass and stress changes induced by mining activities is crucial for structural stability monitoring and disaster early warning. This paper investigates the time–space–intensity distribution of microseismic sources during the pillar-free large-area continuous extraction. Furthermore, it explores a method involving collaborative evolution patterns of the velocity field and spatial b-value to identify stress and structural changes at the panel stope. Results show that anomalous zones in wave velocities and b-values form at the intersections of extraction drifts, strike drifts, cross drifts, and connection roadways influenced by mining activities, as well as in footwall ore-rock contacts, often accompanied by the nucleation of microseismic events. The synergistic use of wave velocity fields and spatial b-value models reveals the relationship between stress migration behavior and stope structure changes due to mining disturbances. The velocity field primarily reflects macroscopic changes in the structure and stress distribution, while spatial b-values further explain stress gradients in specific areas. Additionally, we have advanced the identification of an instability disaster at the connection roadway and cross drift intersection based on increases in wave velocity and abnormal changes in b-value. This paper demonstrates the potential of risk identification using the proposed method, providing insights into predicting geotechnical engineering disasters in complex stress environments.

Stability assessment of surrounding rock in downward mining route supported by slab-wall backfill structure

Characteristic of ground pressure in surrounding rock is generally considered as the theoretical basis of parameter optimization for stope structure and technology. To explore the feasibility of efficient method for the second-step downward route backfill stopes in Shanjin gold mine, various numerical simulation methods were used to investigate the effect of slab-wall backfill structure on stability of surrounding rock in downward route mining system. The maximum principal stress, artificial false roof stress, and displacement were analyzed to evaluate the level of ground pressure in different mining areas. These results indicate the optimized structural parameters for backfill stopes, which may also provide a low-cost way to achieve a high safety for downward route mining system.

Gas-Solid Flow Characteristics of Airflow and Dust Particles in Blasting Excavation of Underground Metal Mine Tunnels.

Effective dust removal has long been a challenge in the blasting mining of underground metal mine tunnels, and uncontrolled dust diffusion seriously endangers workers' respiratory systems and the underground space safety environment. However, the vast majority of existing numerical studies on dust diffusion are focused on coal mine fully mechanized mining, which is different from metal mine blasting excavation in terms of stope structure and dust properties. Furthermore, the mechanism by which the forced and exhaust ventilation modes affect the diffusion characteristics of inhalable particles is unclear. In this work, gas-solid flow characteristics for dust diffusion in a typical metal mine blasting tunnel were numerically investigated based on the Euler-Lagrange method, where the blasting face instantly released 6.37 × 107 particles with 100 different sizes, ranging from 0.8 to 200 μm. The interphase forces between airflow and dust particles are comprehensively modeled, and the particle diffusion effect caused by fluid turbulence is described by a discrete random walk model. Detailed information for airflow turbulence and particle migration was revealed, and dust removal efficiencies for inhalable particulate matter (PM10) by forced, exhaust, and hybrid ventilation were analyzed. Numerical results predict a complex airflow pattern in the working roadway, including the jet-flow region, return airflow core region, airflow disorder region, and secondary flow region. Dust diffusion temporal characteristics can be divided into three stages, namely, the initial stage of dust generation, the efficient ventilation and dust removal stage, and the later stage of dust diffusion. Dust diffusion spatial characteristics indicate that under the Coanda wall attachment effect, the dust concentration exhibits nonuniform distribution in both vertical and horizontal directions of the return air roadway. The dust removal efficiency of hybrid ventilation on inhalable particles above respiratory height is better than that of forced ventilation, especially in the return air roadway. The additional exhaust air duct based on forced ventilation can discharge more inhalable particles from the tunnel.

Optimization of stope structure parameters by combining Mathews stability chart method with numerical analysis in Halazi iron mine

When employing the open stope mining method for extracting materials in underground mines, it is necessary for personnel and equipment to operate within a specified range of the goaf area, thus, adoption of appropriate mining parameters in the mining field is crucial for promoting safe production practices. In this study, the Harazi iron mine is taken as the research subject, with theoretical analysis combined with numerical simulation that enables the authors to simulate and analyze the width parameter of the mining field. Theoretical analysis utilizing the Matthew stability chart method confirms that the width of the mining field in Harazi iron mine should not exceed 9 m. Based on this finding, the mechanical response characteristics accompanying the mining process at different widths within the mining field limits are analyzed via the Flac3D numerical analysis software. As a result of this analysis, the optimal width of the mining field in Harazi iron mine is determined to be 8 m. The method utilized in this article provides a rational approach to determining structural parameters of the mining field and can effectively aid in promoting mine safety practices.

Comprehensive evaluation method of stope stability and its application in deep metal mine.

The problem of high stress conditions is a critical challenge for mining activity in deep metal mines, and the difficulty and economic cost of maintaining stope stability also increases. In order to ensure stope stability in the mining process, it is necessary to evaluate stope stability for a more stable stope structure. However, there are many kinds of methods for rock stability assessment, and most of them are based on empirical and analytical methods, which lead to uncertain results. In this paper, a comprehensive evaluation method including factors of stope stability, self-stabilization time, maximum safety span, and support measure is determined, which is more likely to provide a comprehensive result. Finally, it was verified by the field application in Jiaojia Gold Mine. Results show that it can accurately evaluate the stope stability from different aspects compared with the traditional single evaluation method, and it leads to a more comprehensive and reliable result.

Design Method and Application of Stope Structure Parameters in Deep Metal Mines Based on an Improved Stability Graph

Deep mining has become an inevitable trend of mining development. Previously conducted studies have established that reasonable stope structure parameters are the premise to ensure the safe and efficient production of deep mines. In order to ensure the safety of deep mining, in this paper, we systematically review the existing stope structure parameter design methods, and then put forward a deep stope structure design method based on the stability of mining rock mass. Based on rock mass quality classification, this method uses a critical span graph and an improved stability graph, and fully considers the influence of joint occurrence and mining stress on the stability of surrounding rock, to design the stope structural parameters. Taking into consideration the deterioration of the quality of deep rock mass, we collect mining data at home and abroad, improve the stability graph, and make it suitable for the design of stope structural parameters with different mining methods. The design process of stope structural parameters is expounded through field engineering cases, and it has specific guiding significance for the design of stope structural parameters in deep metal mines.

Stability Evaluation and Structural Parameters Optimization of Stope Based on Area Bearing Theory

A reasonable and stable stope structure is the premise of realizing safe mining of underground metal ore. To safely mine the gently inclined medium-thick ore body, stope stability in Bainiuchang Mine was analyzed based on the pillar area bearing theory, and stope stability with regard to nine groups of structural parameters was numerically simulated. The results show that the existing stope structural parameters failed to maintain stability requirements and tended to be exposed to the risk of stope collapse. The middle section of the pillar as well as stope roofs and floors are vulnerable due to tensile stress when mining by open stoping, and the compressive stress concentration is prone to occur at the junction of the pillars, stope side walls, roofs and floors. Shear stress contributes little to pillar failure. The reasonable stope structural parameters of open stoping for the gently inclined medium-thick ore body in Bainiuchang mine are optimized using ANSYS numerical simulation: stope height 4.5 m, pillar diameter 4 m, pillar spacing 7 m and pillar row spacing 8 m. The onsite trial shows that the ore recovery rate reaches 82% under these parameters, which also realizes the equilibrium of safety and economy.

Study on Optimization of Stope Structural Parameters and Filling Scheme of Wawu Phosphate Mine in Yichang City, China

Reasonable stope structural parameters are very important to ensure the safety and efficiency of mining. In this paper, based on the elastic-plastic constitutive model of Mohr-Coulomb strength criterion, the reasonable span and critical span are calculated by using simply supported beam theory and mine room width calculation formula. PLAXIS2D finite element analysis software was used to conduct numerical simulation research on 7 m × 9 m, 5 m × 12 m stope structure parameter schemes and 7 m × 9m, 5 m × 12 m waste rock filling schemes. The optimal structure parameters of the stope were determined based on the calculation and analysis of displacement variation rule, surrounding rock stress distribution and plastic zone. The analysis and simulation results show that Case 1 one-time mining 7 m × 9 m and Case 3 one-time mining 5 m × 12 m, the plastic zone is connected, the simulation calculation is not convergent, and the stope is unstable. Case 2 waste rock filling 7 m × 9 m and Case 4 waste rock filling 5 m × 12 m, the distribution and change of stress, displacement and plastic zone in the goaf under the two cases are compared, and finally the waste rock filling 7 m × 9 m is obtained can improve the economy and safety of mining in the mining area, and verify the feasibility of implementing stope structural parameters and waste rock filling mining system is verified.

Study on Optimization of Stope Structure Parameters for Steeply Inclined Medium-thick Broken Ore Bodies

Study on Optimization of Stope Structure Parameters for Steeply Inclined Medium-thick Broken Ore Bodies

Optimization of Stope Structure Parameters Based on the Mined Orebody at the Meishan Iron Mine

Based on the engineering background of the Meishan iron mine with sublevel caving (SLC) method, in this work, we adopted the method for identifying the shape of mined orebody (the original location in blasted slice), which analyzed and determined reasonable stope structure parameters. In the field test, the markers were arranged in the blasted slice, the mined orebody was measured by in situ tests, and reliable data were achieved. The shape of the mined orebody was obtained through this test when the width of drift was 6 m. The mined orebody’s shape was compared with the shape of the isolated extraction zone (IEZ), and the difference increased with increasing height. When the stope structural parameters were determined by the mined orebody, the larger the sublevel height was, the smaller the error was, which was compared with the method using ellipsoid arrangement theory to determine the stope structural parameters. Finally, the reasonable stope structure parameters were optimized. The sublevel height was 22 m, and the drift spacing was 20 m.

A path for evaluating the mechanical response of rock masses based on deep mining-induced microseismic data: A case study

Deep, high-intensity mining has become a general development trend in mineral resource extraction operations. Under deep mining conditions, high-intensity mining renders the mechanical environment more complicated. The strong disturbance caused by excavating ore-bearing rocks may trigger ground-pressure-induced disasters, and the associated disaster mechanism is more complex. In the mining of deep metal orebodies, stope stability has been a crucial factor restricting mining safety. In response to the above problems, a path for evaluating the mechanical response of surrounding rocks using mining-induced microseismic (MS) data was proposed and applied to a test stope of the Xiadian Gold Mine, which has experienced stope instability as a result of deep mining. First, MS data received before, during, and after the mining of the test stope were analyzed to explore the evolution of MS events, the failure mechanism, and the evolution of fractures during different stages. Subsequently, by utilizing the method for calculating the damage, seismic stress, and seismic strain defined by the moment tensor (MT), the dynamic response trends of damage, stress, and strain during the mining of the test stope were investigated. Finally, the proposed damage model based on fractures derived from MS data was mapped into a finite element numerical analysis. According to the time sequence of the stope mining, the rock mass parameters were dynamically weakened to investigate the changes in the plastic zone and the displacement of the test stope under the original and new stope structures and determine the stability of surrounding rocks under the new stope structure. The research is expected to aid in the mining design and support design of deep mines and provide a reference for the same type of mines elsewhere.

Optimization of Structural Parameters of Stope without Sill Pillar in Metal Mine by Computer Numerical Simulation

The determination and optimization of stope structure parameters is of great value in reducing the ore loss and dilution in the mining process, improving the production capacity of the stope, increasing the workload of mining and mining, reducing the investment cost of the mine and improving the mining efficiency. Based on this, this paper first analyses the parameter changes of stope structure parameters without sill pillars in metal mines, and then studies the optimization of structural parameters of stopes without sill pillars in metal mines based on orthogonal test method.

A Dynamic Intersecting Arrangement Model Based on Isolated Draw Zones for Stope Structure Optimization during Sublevel Caving Mining

In this paper, stope structure optimization during sublevel caving mining is considered under the condition that the isolated draw zones (IDZs) are nonstandard ellipsoid, which is realized by dynamically adjusting the arrangement of IDZs and quantifying the degree of intersection of IDZs according to an ore profit and loss calculation model. A dynamic intersecting arrangement model based on IDZs was proposed, which can dynamically adjust the sublevel height and drift spacing according to the ore-rock bulk flow parameters, economic indicators, occurrence condition of the ore body, drilling machine, and so forth. Based on the model, the range of drift spacing, the lower volume of crestal residual ore, and the higher volume of mixing waste rock are calculated. By deducing the function of ore profit and loss, a calculation model for ore profit and loss is established to quantify the degree of intersection of IDZs and determine the best stope structure. Using the constructed dynamic intersecting arrangement model, a stope structure of −213 m to −303 m in the Yanqianshan Iron Mine was designed, with a sublevel height of 22.5 m and a drift spacing of 20.5 m. A physical drawing model was designed, and three physical simulation experiment schemes were conducted to compare and analyse the ore loss and dilution of the intersecting arrangement model and the traditional tangent arrangement model. The results showed that the loss rate decreased by 3.66% and the dilution rate increased by only 0.22%, thus verifying the effectiveness and applicability of the model to optimize the stope structure.

Stope structure evaluation based on the damage model driven by microseismic data and Mathews stability diagram method in Xiadian Gold Mine

To obtain a better economic benefit, Xiadian Gold Mine intended to increase the stope structure parameter from 2.5 m (height) to 8 m. A test stope using the new structure parameter was mined to verify the surrounding rock’s stability. Based on the mechanical indices relating to the ore and rock, the “static” stability of the test stope under the new stope structure was analyzed by the Mathews stability diagram method. Then, a microseismic (MS) monitoring system was installed around the test stope to determine the “dynamic” stability of the test stope during mining. The spatio-temporal evolution of MS events was analyzed to understand the failure behaviors of the surrounding rock. Based on the MS monitoring results, a damage model was established and used to quantify the damage degree and dimension within the surrounding rock during mining the test stope. The study results show that the damage degree increased from less than 0.05 to 0.6, the damage dimension increased from less than 1500 m2 to more than 14,000 m2, and the shear plastic zone appeared around the two sidewalls and the roof of the stope. The results show that the test stope is at risk of instability under the new stope structure.

The Application of Destress Mining Technology in Deep High Stress Stope of a Submarine Mine

Feng, P.; Yang, X.; Guo, Q.; Wang, H., and Wan, C., 2020. The application of destress mining technology in deep high stress stope of a submarine mine. In: Liu, X. and Zhao, L. (eds.), Today's Modern Coastal Society: Technical and Sociological Aspects of Coastal Research. Journal of Coastal Research, Special Issue No. 111, pp. 34–38. Coconut Creek (Florida), ISSN 0749-0208.The deep ore rock of a submarine gold mine had strong rock burst tendency. The difference between its maximum principal stress and minimum principal stress was large, and the surrounding rock deformation and failure were serious. A combined regional and local destress mining technology for the high stress submarine environment was proposed and applied to deep stope in coastal deposit. Regionally, the stope structure and stope sequence were optimized to reconstruct the favorable ground stress environment. Locally, the destress engineering was arranged rationally to interfere with the transmission path of the maximum principal stress. Meanwhile, the pillar was supported by flexible cooperative support with shotcrete and anchor net. The (stress and strain) in situ monitoring indicated that the stress in submarine stope appeared three-dimensional balanced distribution after destress, and the surrounding rock deformation of submarine roadway tended to be stable, achieving the expected destress mining effect in coastal high stress deposit.

Optimum Sublevel Height and Drift Spacing in Sublevel Cave Mining Based on Random Medium Theory

Weak rock mass and poor flow of material can cause excessive ore loss and dilution in sublevel caving. This paper proposes a method to establish design parameters for an inclined deposit within a weak rock mass and evaluates its effectiveness through a case study. In order to solve the problem of low production capacity and poor safety conditions of sublevel caving mining at the Yingfangzi silver mine in China and to ensure a smooth production from the refractory ore body, it is necessary to select appropriate stope structure parameters. Based on random medium theory of gravity flow and the improved equation of ore discharge in random medium, an end wall drawing experiment is carried out to determine the optimum design and flow parameters. It was observed from the experiment that, due to the influence of the randomness of particle movement, there is a mismatch in the flow parameter measurement. The flow characteristics and distribution of the marker particles are different from that of the tested particles resulting in large drawbody shape distortion. The study finds that the flow parameters obtained by the new method are more practical and account for drawpoint width and recommends that the new method for determining the sublevel stope height is used when the drawbody is a non-standard ellipsoid. The outcomes have shown a significant reduction in the dilution and improvement in the recovery rates, and the safety and efficiency of mining have been greatly improved.

Study on the Allowable Exposure Time of Temporary Goaf in the Open Stope and Backfill Mining Method with Large Structure Parameters

Based on the uniaxial rheological experiment data of iron ore rock mass and filling body in large‐scale stope obtained by using the rock servo controlling creep equipment, the characteristics of the creep curve were analyzed. The creep models of iron ore and filling body which can show the attenuation creep of rock were constructed. And a nonlinear creep model was obtained. According to the rheological data of the iron ore and the filling body, the parameters of the new nonlinear creep model were identified to obtain the material parameters of the creep model. Then, the creep model parameters were fitted and reduced to calculate the reasonable exposure time of temporary goaf in the large‐scale stope. The results show that the reasonable exposure time of stope is 520 ～ 650 days, and the reasonable exposure time of filling body is 410 ～ 520 days. The model can well describe the initial attenuation creep stage and steady creep stage in the creep curve, which proves the correctness and rationality of the model. The study provides a reference for mining design and safety production of similar mines with large‐scale stope structure.

Stability of stope structure under different mining methods

The ore body has a great influence on the stability of surrounding rock and mining safety under different mining modes, and the reasonable selection of mining mode depends on other characteristics, such as ore structure surface feature, rock mass mechanical property, and ground stress distribution. Given the insufficient mining research data, this study establishes a 3D model by using the FLAC3D calculation program. Through numerical simulation and other technical means, a preliminary study on plastic and minimum stress changes during horizontal pillar mining, stress changes under different mining modes, and the effect comparison of full filling mining modes is conducted. Results show that the surrounding rock at the corner of pillar 1 is damaged, the plastic zone decreases, and the minimum stress in each working procedure increases slightly. The area of the plastic zone in alternate mining is smaller to that in continuous mining. This study provides a theoretical basis for ore body mining.

Optimization calculation of stope structure parameters based on Mathews stabilization graph method

Mathews stability graphic method, based on the rock classification system, measures the stability of the ore roof area of a relatively simple calculation method and provides a theoretical basis for mine rational design stope structure size parameters. In this study, we used a large-scale tungsten mine in Jiangxi Province as the engineering background and performed on-site engineering geological surveys and indoor ore rock mechanics tests in the middle section of mine 417 to obtain multiple engineering quality indicators for the mines and surrounding rocks. The Mathews stability map method and Barton limit span theory were used. The reasonable size range of the exposed face of the stope was calculated by performing theoretical analysis on the ultimate span. Then, FLAC3D calculation and analysis software were used for the simulation of the stope structure, and the most reasonable design of the exposed surface dimension was selected and used as reference for ensuring the safe production of the mine.

Mining Scheme Optimization and Stope Structural Mechanic Characteristics for a Deep and Large Ore Body

Several large ore bodies are exposed to poor environments. Thus, designing a reasonable mining scheme for the stress characteristics and stability of stope structures is essential. In this study, Fast Lagrangian Analysis of Continua 3D is used to study the stability and mechanics environment of the surrounding rock and cemented pillars in two kinds of mining scheme for continuous mining and “taking one every other one” mining. The mechanical response of stope structure to each process under different mining schemes is analyzed from the aspects of vertical stress, vertical displacement and stress distribution. The results show that, during the “taking one every other one” mining process, the maximum principal stress is between 0 MPa and 5 MPa, the vertical maximum displacement is 25 mm and the vertical stress range is 0–14 MPa. These simulation parameters are obviously better than continuous mining scheme. This mining scheme is more conducive to stope stability, increasing mine economic efficiency and ensure production safety.