Mine Design Research Articles

Evaluation of physical and environmental working conditions of underground coal mines within the framework of ergonomics

This study evaluated the physical and environmental working conditions of underground coal mines and the occurrence of musculoskeletal symptoms (MSS). The data from 236 miners were collected and analysed by using the chi-squared test, Fisher's exact test, and the Mann-Whitney U test. Results showed that mine design was inappropriate (e.g., lack of appropriate tools and inadequate working conditions, etc.). Miners had to deal with excessive job demands (e.g., inappropriate work pace, high manual material handling (MMH), and repetitive tasks). Most miners (85.5%) experienced pain/discomfort in at least five body regions. Low back (82.6%), upper back (80.9%), shoulder (77.5%), knee (67.8%), and ankle/foot (62.3%) complaints were the most frequently reported symptoms. The low back symptoms were associated with MMH tasks, shoulder symptoms were associated with poor lighting conditions, and ankle/foot symptoms were associated with inappropriate work pace, inadequate space, pushing/pulling/dragging tasks, and bending/twisting activities. The findings help to understand the working conditions of miners and highlight the need for multifaceted interventions to improve the workstation design and work organisation.

Development of a multiple level underground limestone mine from geology through mine planning

The development of a multiple level underground mine is a complex task in which geology, engineering, ground control, and unit operations are integrated into a single mine design. The components are inter-dependent and must function cohesively to ensure a profitable underground mining operation. To optimize reserve recovery, mine planning should begin from the lowest level and progress up. This limits any misjudgments or oversights of a given level affecting the underlying levels and ensures the ability to maximize recovery from each level. Mine planning should start with the exploration and characterization of the geologic setting. Once the reserve geology and quality is well understood, then mine planning can begin with respect to the following: (1) orientation of mine works with respect to horizontal stress; (2) access to the reserve; (3) determination of opening widths; (4) selection of back, floor horizons and pillar centers; (5) selection of development and secondary mining heights; (6) appropriate inter-burden thicknesses; and (7) examining the stability of the multiple level mine through numerical modeling. The multiple level mine design process and decisions are presented through a case history example. The theme is that there is one opportunity to “get it right” and many chances to overlook a small aspect within the design that will plague the mine throughout all levels and through the entirety of its operating life.

Mechanical behaviour and failure characteristics of cemented paste backfill under lateral unloading condition

A key issue associated with mine backfill design is the determination of mechanical behaviour and failure characteristics of the cemented paste backfill (CPB), especially for CBP under lateral unloading conditions caused by excavation of adjacent stopes. In this research, a series of lateral unloading tests with RFPA3D were conducted to investigate the relationships among the cement-tailings ratio (1:4 and 1:8), lateral unloading stress (0 MPa, 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa and 1.0 MPa), mechanical behaviour, failure modes and acoustic emissions (AE) characteristics. Similar mechanical behaviour of all the CPB specimens was obtained. With different cement-tailings ratios and preloading stress values, the ultimate failure modes of CPB specimens show different forms. Additionally, increasing the preloading stress value caused a rising of AE counts. The results of this study can provide a significant reference for the backfill design and study of underground mining.

Support Design for Rockburst-Hazardous Underground Mines in Gornaya Shoria

Support Design for Rockburst-Hazardous Underground Mines in Gornaya Shoria

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.

Mechanical behaviour and failure characteristics of cemented paste backfill under lateral unloading condition

A key issue associated with mine backfill design is the determination of mechanical behaviour and failure characteristics of the cemented paste backfill (CPB), especially for CBP under lateral unloading conditions caused by excavation of adjacent stopes. In this research, a series of lateral unloading tests with RFPA3D were conducted to investigate the relationships among the cement-tailings ratio (1:4 and 1:8), lateral unloading stress (0 MPa, 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa and 1.0 MPa), mechanical behaviour, failure modes and acoustic emissions (AE) characteristics. Similar mechanical behaviour of all the CPB specimens was obtained. With different cement-tailings ratios and preloading stress values, the ultimate failure modes of CPB specimens show different forms. Additionally, increasing the preloading stress value caused a rising of AE counts. The results of this study can provide a significant reference for the backfill design and study of underground mining.

THE INFLUENCE OF DISCONTINUITIES ON ROCK MASS QUALITY AND OVERALL STABILITY OF ANDESITE ROCK SLOPE IN WEST JAVA

Open-pit mining constitutes a necessary activity for the extraction of rocks and minerals from the Earth. However, open-pit mining activities often result in rock slope stability issues related to the discontinuities of rock masses. Thus, an appropriate cut-slope design in open-pit mining requires good knowledge of the effects of discontinuity on rock mass strength and quality. This study aims to analyze the effect of discontinuity type on rock quality and slope stability. Discontinuity data was collected from the columnar jointed-andesite rock slope in West Java. The analysis showed that the examined andesite slope has a good rock mass quality and very favorable slope stability. However, wedge-type slope failure may occur, which is substantially affected by columnar joints present in the rock mass. Moreover, the analysis indicated that the integral discontinuities present in the andesite outcrops significantly affect the mean values of the discontinuity length, discontinuity spacing, and rock strength. However, the integral discontinuities have little effect on the slope mass rating (SMR). Thus, detailed studies on the contribution of integral discontinuities to the rock mass rating and SMR of different rock types are recommended.

Experimental research of gold migration influenced by cyclic flooding-drainage of rock mass

Efficient development of man-made placers is subject to the introduction of new technological solutions, as well as implementing the possibility of choosing the optimal design and technological indicators of mining and processing equipment, depending on the combination of influencing natural, design and technological factors. The most important research goal is the invention of new innovative technologies. To solve these problems, the direction of research on the development and theoretical substantiation of geotechnology for the development of technogenic alluvial deposits was determined and is being developed on the basis of the intra-dump concentration of valuable components, which ensures the formation of an enriched zone in the near-bed area. In order to develop the technology, the authors carried out large-scale theoretical and experimental studies to study the nature and degree of influence of a number of factors that form the basis of the technology on the migration and concentration of gold particles in the man-made rock mass, as well as determining the technological parameters and modes of flooding and drainage of the rock mass.

Application of modern information technology in the design of underground mining

Application of modern information technology in the design of underground mining

Prediction of rock properties using grinding characteristics of ball mill

Knowledge of physico-mechanical properties of rocks is essential starting from the preliminary exploration to processing in mining projects. The strength properties of rocks considered necessary for mine planning and design, selection of equipment, use of suitable processing technique, etc. Sophisticated laboratory facilities are required to determine various properties of rocks using some international standards like ISRM, ASTM, etc., which is time consuming and costly affair. In this study, an attempt is to predict some of the rock properties like density, tensile strength using grinding characteristics of ball mill. Laboratory experiments conducted on samples of granite, limestone, slate and BHQ varying different parameters like quantity of feed, charge ratio, size of balls, grinding time, etc., at constant RPM of ball mill. Grinding characteristic curves used to obtain 25%, 50%, 80% cumulative passing sieve sizes. In addition, laboratory experiments carried out to find physico-mechanical properties like density, tensile strength, Protodyakonav's strength index, rebound hardness number. Regression analysis carried out with the data obtained from experiments.

A practical, long-term production scheduling model in open pit mines using integer linear programming

SYNOPSIS Long-term production scheduling is a major step in open pit mine planning and design. It aims to maximize the net present value (NPV) of the cash flows from a mining project while satisfying all the operational constraints, such as grade blending, ore production, mining capacity, and pit slope during each scheduling period. Long-term plans not only determine the cash flow generated over the mine life, but are also the basis for medium- and short-term production scheduling. Mathematical programming methods, such as linear programming, mixed integer linear programming, dynamic programming, and graph theory, have shown to be well suited for optimization of mine production scheduling. However, the long-term plans generated by the mathematical formulations mostly create a scattered block extraction order on several benches that cannot be implemented in practice. The reason is the excessive movement of mining equipment between benches in a single scheduling period. In this paper, an alternative integer linear programming (ILP) formulation is presented for long-term production scheduling that reduced the number of active benches in any scheduling period. Numerical results of the proposed model on a small-scale open pit gold mine show a 34% reduction in the average number of working benches in a given scheduling period. Keywords: long-term production scheduling, mathematical programming, practical plans, equipment movements.

Prediction of rock properties using grinding characteristics of ball mill

Knowledge of physico-mechanical properties of rocks is essential starting from the preliminary exploration to processing in mining projects. The strength properties of rocks considered necessary for mine planning and design, selection of equipment, use of suitable processing technique, etc. Sophisticated laboratory facilities are required to determine various properties of rocks using some international standards like ISRM, ASTM, etc., which is time consuming and costly affair. In this study, an attempt is to predict some of the rock properties like density, tensile strength using grinding characteristics of ball mill. Laboratory experiments conducted on samples of granite, limestone, slate and BHQ varying different parameters like quantity of feed, charge ratio, size of balls, grinding time, etc., at constant RPM of ball mill. Grinding characteristic curves used to obtain 25%, 50%, 80% cumulative passing sieve sizes. In addition, laboratory experiments carried out to find physico-mechanical properties like density, tensile strength, Protodyakonav's strength index, rebound hardness number. Regression analysis carried out with the data obtained from experiments.

Entropy Evaluation Method for Sandstone Uranium Reservoir Characteristics Based on Convex Hull Search

The continuity and homogeneity of sandstone uranium deposits are inherent characteristics that affect in situ leaching performance indexes and have important guiding effects on the optimization of mining design. In this work, we propose a spatial information entropy calculation method based on a convex hull search strategy to quantitatively evaluate the geological characteristics of uranium deposits. We use the 3-D block model of sandstone-hosted uranium deposits as hard data. First, we use the Alpha-Shapes algorithm to calculate the convex hull of the space area where various types of unit blocks are located. Second, we formulate a suitable multi-point configuration based on the convex hull size. Then, we use the multi-point density function. Scanning the convex hull point cloud establishes a probability density function to calculate the local information entropy of various sub-regions. Finally, the local spatial information entropy is aggregated using addition and multiplication to obtain the joint spatial information entropy of the entire evaluation area. A series of parameter sensitivity and performance analysis experiments prove the stability of the method and the accuracy of the quantitative and homogeneous evaluations of the complex geological conditions. In order to solve the problem of the difference between the designed production capacity and actual production capacity of a uranium deposit, we use a new method to evaluate the homogeneity and continuity of the lithology and grade of the deposit. The new method and evaluation conclusions can be used for the automation and understanding of future engineering optimization processes.

Analysis of panel design experiments in advanced longwall mines

Panel design and its geometry affects the productivity, strata control and operational costs of longwall mining. Selection the suitable panel size is a critical stage which needs a wide range of geological, technological and economical inputs. Seam height and overburden are two uncontrollable factors which play an important role in longwall mine design. Panel width, panel length and layout of whole mine are main design parameters which are selected based on uncontrollable factors and technological restrictions. In this paper the geometrical characteristics of 61 longwall panels in 46 operating mines of USA have been applied for statistical analysis and extracting some experimental design benchmarks. The analysis shows that average seam height, panel overburden, panel width and panel length are 2.26, 200, 361.5 and 3455 respectively. Average panel width to depth ratio is 1.53 and panel length to width ratio is 9.55. The 3D data analysis reveals that overburden is more important than seam height in enlargement of longwall panels and maximum of the panel area (panel length multiplied by panel width) occurs when the overburden is between 150 to 250 meters and seam height is from 1.5 to 2.5 meters. Also, 50 percent of the studied advanced longwall panels the width to depth ratio varies from one to two. It confirms that even in shallow panels the designers have selected larger panel dimensions to enhance the productivity by considering some subsidence problems and high caving pressures.

Numerical Simulation Investigation of Seismic Dynamic Response of Pillars in Underground Goaf

In order to obtain the dynamic response law of pillars in underground goafs under the action of seismic wave, the acceleration response and dynamic displacement response law of pillars were studied by using the MIDAS-GTS/NX finite element simulation software based on a mine. Results are shown as follows: (1) the response of the top acceleration and displacement of the pillar and roof of goaf is larger than that of the bottom. (2) The cross-sectional area of pillars has a significant effect on the dynamic response of pillars in underground goafs. The stability of pillars with large cross-sectional area is generally better. (3) The position of pillars has a significant effect on the dynamic response of pillars. The dynamic response of pillars in the center of goaf is the strongest. However, the dynamic response of pillars in the edge of goaf is smallest. (4) The laws of acceleration and displacement response of pillars in goafs under horizontal seismic wave are revealed, which provides reference for mining design and earthquake damage prevention.

Understanding roof deformation mechanics and parametric sensitivities of coal mine entries using the discrete element method

Although conventional coal mine designs are conservative regarding pillar strength, local failures such as roof-falls and pillar bursts still affect mine safety and operations. Previous studies have identified that discontinuous, layered roof materials have some self-supporting capacity. This research is a preliminary step towards understanding these mechanics in coal-measure rocks. Although others have considered broad conceptual models and simplified analogs for mine roof behavior, this study presents a unique numerical model that more completely represents in-situ roof conditions. The discrete element method (DEM) is utilized to conduct a parametric analysis considering a range of in-situ stress ratios, material properties, and joint networks to determine the parameters controlling the stability of single-entries modeled in two-dimensions. Model results are compared to empirical observations of roof-support effectiveness (ARBS) in the context of the coal mine roof rating (CMRR) system. Results such as immediate roof displacement, overall stability, and statistical relationships between model parameters and outcomes are presented herein. Potential practical applications of this line of research include: (1) roof-support optimization for a range of coal-measure rocks, (2) establishment of a relationship between roof stability and pillar stress, and (3) determination of which parameters are most critical to roof stability and therefore require concentrated evaluation.

Experimental Study on Rheological Properties and Strength Variation of High Concentration Cemented Unclassified Tailings Backfill

This experimental study presents the rheological properties and strength characteristics of cemented unclassified tailings backfill (CUTB). The particle size distribution and chemical properties of tailings from the Shizhuyuan lead‐zinc mine were examined experimentally. A series of rheological properties and uniaxial compressive strength (UCS) tests were conducted to study the relations between the rheological properties of CUTB and two factors of cement‐tailings ratio (c/t) and solid content (SD). The two‐factor nonrepetitive analysis of variance (ANOVA) method was used to study the sensitivity of rheological properties to two factors of c/t and SD. Relations between UCS performance of CUTB and c/t, SD, and curing time (CT) were discussed. Results indicate that CUTB samples exhibit obvious shear thinning characteristics and the rheological process is the result of multiple rheological model composites. Yield stress and viscosity of CUTB increase with the increase of SD and c/t as quadratic. The solid content is the most important factor for the rheological properties of CUTB, followed by c/t. UCS of CUTB increases exponentially with the increase of SD and increases with c/t as quadratic. The larger the ratio of c/t, the greater the influence of the CT on the increasing strength of CUTB. The smaller the c/t, the slower the increase of the CUTB’s strength with the increase of the SD. The findings of this study can provide the efficient mix proportion of backfill slurry for the backfill mining design, so as to have better performance of the underground mining structure and reduce the cost of backfill mining.

Application of Foam Stopping for Mitigation of Spontaneous Heating In Underground Coal Mines

The problem of spontaneous heating is a major threat to safety and productivity in mines all over the world. In India, more than 80% of fires are caused due to Spontaneous Combustion. The applicability of inert gases is expensive, time-consuming and is a very tedious process. Hence the application of advanced technologies becomes essential to be introduced in mines. In this context, Central Mine Planning and Design Institute (CMPDI), Ranchi, India carried out an R&D project entitled “Construction of quick setting stopping in case of fire in an underground mine using expansion foam agent” under the funding from the Ministry of Coal, Government of India. Under this project, two Indian mines were selected in consultation with MCL for carrying out the proposed work in Orient Mine No.3 and Bundia Mine of MCL (Ib Valley AREA). Coals from both the mines have been collected and analysed in the laboratory. The proximate analysis and CPT/IPT results show that both the coals are moderately prone to spontaneous heating. Considering both intrinsic and extrinsic properties, two stoppings were constructed in the Hirakhand Bundia mines and four in orient mines. Periodic supervision along with the altering ingress of air from intake was been checked. After careful supervision of nearly 4 years, the stoppings proved to be strong enough to be leakage proof. This paper describes the application of foam technology as stopping to avoid air entry, thus preventing the occurrences of spontaneous heating/fire in a panel of Indian coal mines.

Strain energy evolution and conversion under triaxial unloading confining pressure tests due to gob-side entry retained

To increase the recovery rate of coal mining operations, the gob-side entry retained (GER) technique has been extensively implemented in China. However, due to the mining-induced macro-cracks in the immediate roof above the roadside backfill area (RBA) under cyclic loading, the roof failure may occur and threaten the safety of GER. Mechanical characterization of rocks is crucial for understanding of the failure mechanism of this roof failure phenomenon. Based on the theoretical analysis and triaxial unloading confining pressure tests with cyclic loading on sandy mudstone, the strain energy evolution and conversion were studied. Results indicate that the total strain energy, elastic strain energy, and plastic-damage strain energy can be divided into various stages during the test. An index was introduced to describe the energy conversation and deformation of damaged rock specimen during the test, which can be expressed as the ratio of the plastic-damage strain energy to the total strain energy. This index increases gradually from the peak point to the post-peak unloading point. Then, it increases sharply from the first axial stress level to the first failure state, and finally decreases from the second axial stress level to the second failure state. Failure patterns of the damaged rock suggest that the macro-shear failure bands are mainly caused by the axial compression, whereas the micro-crack propagation is due to the circumferential expansion. The findings on the strain energy evolution and conversion of the immediate roof under the loading and unloading conditions of GER provides an insightful method to evaluate the roof stability above RBA, which also sheds lights on the GER design in coal mining to prevent the roof failure above RBA.

Automated Core Logging Technology for Geotechnical Assessment: A Study on Core from the Cadia East Porphyry Deposit

Abstract The Cadia East porphyry deposit, located approximately 20 km south of Orange, New South Wales, Australia, contains a significant resource of copper and gold. This resource is hosted within the Forest Reefs Volcanics and is spatially and temporally associated with the Cadia Intrusive Complex. To extract ore, the underground mine currently uses the block cave mining method. The Cadia East geotechnical model provides data inputs into a range of numerical and empirical analysis methods that make up the foundation for mine design. These data provide input into the construction of stress models, caveability models, ground support design, and fragmentation analysis. This geotechnical model encompasses two commonly used rock classification systems that quantify ground conditions: (1) rock mass rating (RMR) and (2) rock tunneling quality index (Q index). The RMR and Q index are calculated from estimates of rock quality designation (RQD), number of fracture sets, fracture roughness, fracture alteration, and fracture spacing. Geologists and geotechnical engineers collect information used to produce these estimates by manually logging sections of drill core, a time-consuming task that can result in inconsistent data. Modern automated core scanning technologies offer opportunities to rapidly collect data from larger samples of drill core. These automated core logging systems generate large volumes of spatially and spectrally consistent data, including a model of the drill core surface from a laser profiling system. Core surface models are used to extract detailed measurements of fracture location, orientation, and roughness from oriented drill core. These data are combined with other morphological and mineralogical outputs from automated hyperspectral core logging systems to estimate RMR and the Q index systematically over contiguous drill core intervals. The goal of this study was to develop a proof-of-concept methodology that extracts geotechnical index parameters from hyperspectral and laser topographic data collected from oriented drill core. Hyperspectral data from the Cadia East mine were used in this case study to assess the methods. The results show that both morphological and mineralogical parameters that contribute to the RMR and Q index can be extracted from the automated core logging data. This approach provides an opportunity to capture consistent geologic, mineralogical, and geotechnical data at a scale that is too time-consuming to achieve via manual data collection.