Mine Layout Research Articles

Coal Mining Induced Seismicity in the Ruhr Area, Germany

Over the last 25 years mining-induced seismicity in the Ruhr area has continuously been monitored by the Ruhr-University Bochum. About 1,000 seismic events with local magnitudes between 0.7 ≤ ML ≤ 3.3 are located every year. For example, 1,336 events were located in 2006. General characteristics of induced seismicity in the entire Ruhr area are spatial and temporal correlation with mining activity and a nearly constant energy release per unit time. This suggests that induced stresses are released rapidly by many small events. The magnitude–frequency distribution follows a Gutenberg–Richter relation which is a result from combining distributions of single longwalls that themselves show large variability. A high b-value of about 2 was found indicating a lack of large magnitude events. Local analyses of single longwalls indicate that various factors such as local geology and mine layout lead to significant differences in seismicity. Stress redistribution acts very locally since differences on a small scale of some hundreds of meters are observed. A regional relation between seismic moment M0 and local magnitude ML was derived. The magnitude–frequency distribution of a single longwall in Hamm was studied in detail and shows a maximum at ML = 1.4 corresponding to an estimated characteristic source area of about 2,200 m2. Sandstone layers in the hanging or foot wall of the active longwall might fail in these characteristic events. Source mechanisms can mostly be explained by shear failure of two different types above and below the longwall. Fault plane solutions of typical events are consistent with steeply dipping fracture planes parallel to the longwall face and nearly vertical dislocation in direction towards the goaf. We also derive an empirical relation for the decay of ground velocity with epicenter distance and compare maximum observed ground velocity to local magnitude. This is of considerable public interest because about 30 events larger than ML ≥ 1.2 are felt each month by people living in the mining regions. Our relations, for example, indicate that an event in Hamm with a peak ground velocity of 6 mm/s which corresponds to a local magnitude ML between 1.7 and 2.3 is likely to be felt within about 2.3 km radius from the event.

Superiority of neural networks for pillar stress prediction in bord and pillar method

Estimation of pillar stress is a crucial task in underground mining. This is used to determine pillar dimensions, room width, roof conditions, and general mine layout. There are several methods for estimating induced stresses due to underground excavations, i.e., empirical methods, numerical solutions, and currently artificial intelligence (AI). AI based techniques are gradually gaining popularity especially for problems involving uncertainty. In this paper, an attempt has been made to predict stresses developed in the pillars of bord and pillar mining using artificial neural network. A comparison has also been done to compare the obtained results with the boundary element method as well as measured field values. For this purpose, a multilayer perceptron neural network model was developed. A number of architectures with different hidden layers and neurons were tried to get the best solution, and the architecture 5-20-8-1 was found to be an optimum solution. Sensitivity analysis was also carried out to understand the influence of important input parameters on pillar stress concentration.

Modeling Uncertainties in Mining Pillar Stability Analysis

Many countries are now facing problems related to their past mining activities. One of the greatest problems concerns the potential surface instability. In areas where a room-and-pillar extraction method was used, deterministic methodologies are generally used to assess the hazard of surface collapses. However, those methodologies suffer from not being able to take into account all the uncertainties inherent in any hazard analysis. Through the practical example of the assessment of a single pillar stability in a very simple mining layout, this article introduces a logical framework that can be used to incorporate the different kinds of uncertainties related to data and models, as well as to specific expert's choices in the hazard or risk analysis process. Practical recommendations and efficient tools are also provided to help engineers and experts in their daily work.

Integrated planning of the partially automated Banji coal mine in China

The chinese mining company SDIC Xinji currently develops in the province of Anhui, south of Beijing, the coal mine Banji, pursuing the aim to realize an exemplary high-performance mine with the highest degree of production efficiency and a high safety standard, using state of the art technology. Remarkable with this assignment of task is the fact, that power supply technology, high voltage switch technology, automation and communication were being projected from one supplier, as an integrated complete system, based on a three- dimensional mine layout model.

Integration of borehole geophysical data in 2D and 3D to develop a hazard index

A borehole hazard index is the integration of interpreted risk indexes with an existing geological and structural 3D mine or exploration model. Individual risk indexes are produced and combined with the purpose of providing a clear visual and quantitative method for determining varying degrees of risk associated with development through a particular geological rock volume. Disparate data sets are used to characterize separate risk indexes established from user defined criteria. Input data sets include geological and structural logs and mine layouts, complemented by a borehole geophysical suite including borehole radar, optical & acoustic televiewers, density, neutron, flowmeter and full wave form sonic. The user defined criteria are established for individual project requirements and can include factors such as the intersection of structures, the presence of water ingress, proximity to structures with specific orientations and the presence of lithological units prone to failure. The requirements of the integration environment vary; certain criteria can be adequately assessed in a 2D environment while other hazard indexes require data to exist in a true topological 3D environment where spatial queries can be performed. The applications of a borehole hazard index include shaft site evaluations, and shaft sinking development planning. Additionally a hazard index can serve as a mine production tool, evaluating hazards in front of the face which will affect both safety and production rates. Successful deployment requires regular and timely update of the local structural model which can be achieved by automating the hazard index generation once the starting model has been defined.

Elastoplastic stability analysis of mine haulage drift in the vicinity of mined stopes

This paper is focused on the interaction between the haulage drift and nearby mining activity related to sublevel stoping method with delayed backfill, one of the most popular mining methods in Canadian underground metal mines. The stability of the haulage drift is examined through a detailed parametric study of a nonlinear, elastoplastic, two-dimensional finite element model representing typical mining layout most commonly adopted in Canadian underground metal mines. The model parametric study examines the influence of critical factors such as the stope mining sequence, mining depth and the distance between the stope and the haulage drift. Stability indicators are defined in terms of displacement, stress and the extent of yield zones, which serve as a basis for assessing the effect of different parameters on the stability of the haulage drift. The model parametric study demonstrates that stope mining causes a footwall lateral shift of the entire drift. The severity of such shift is increased with shorter distance between the stope and haulage drift. Of all mining excavations examined, same-level mining appears to be the most critical. It is also found that more stress relaxation zones and yield zones develop around the haulage drift as the mining depth increases and as distance between haulage drift and the stope decreases.

Network modelling of underground mine layout: two case studies

AbstractThe dominant working structure of an underground mine is a set of interconnected tunnels which provides access to ore zones and haulage of ore from the designated ore zones to the mill. This set of interconnected tunnels forms a network. We describe a mathematical network model and the modelling features of our two software tools for designing underground mine layouts that minimise associated costs. The application of these techniques is illustrated in two industry case studies. In the first, we apply the underground network optimisation tool to design an extension to an Australian gold mine where 15 new distinct orebodies are located in a 3 km long region, several hundred metres underground. In a second case study, we design a single decline for accessing a large orebody where a turning circle constraint is a significant factor. An efficient decline is found using the decline optimisation tool.

A GIS-based Weights-of-Evidence model for mapping cliff instabilities associated with mine subsidence

The Weights-of-Evidence (W-of-E) technique was applied, within a geographic information system (GIS), to derive a model of rockfall potential associated with mining-induced subsidence. The purpose of the model was to describe the potential for rockfalls from up to 60 m high steep sandstone gorges and slopes associated with proposed underground longwall operations within the immediate vicinity of a previously mined area. Ten known rock falls associated with the previous mining operation were used as training points. Six evidential themes were considered-slope, cliff height, planform curvature, profile curvature, the distance of the cliff areas from the longwall panels, and the distance of the cliff areas from the river. Two models were created, one based on a mine layout in which longwall panels extend beneath the steep areas of a nearby river, and a second in which the mine layout is modified so that mining does not occur directly beneath or within 50 m of the steep slopes. This is to allow for the comparison of rockfall potential based on different mining configurations. The results demonstrate that the W-of-E method is a suitable tool for mine subsidence impact assessment, and suggest that not mining directly under the Nepean river may decrease rockfall potential, on average, by approximately ten times. Numerous limitations with the results, relating to the availability of appropriate evidential theme data and the accuracy of training points, are discussed.

A 3D mine simulation model for decision-making in mine design and production

In this paper, the philosophy, methodology, objectives, mining process logic, program structure and its state-of-the-art for our recently developed mine simulation model (a decision-making tool for mine design and production) are discussed. This simulation model is a detailed 3D model that can be used for many different mine sites without the need for programming but requiring only different input data that characterize the mine being simulated. The simulation model generates development, production and performance data throughout mine lifetime. The model also provides economics analyses such as operating cost, revenue, cash flow, rate of return on investment, net present value, ore tons mined and mine lifetime based on simulation results. Further, it studies the sensitivity and risk for the variation of parameters such as ore grade, dilution rate, market price and pre-production investment. The model thus provides all-important information for decision-making in mine design and production. This decision-making tool is very useful for mining projects since it is based on very accurate ore body data (from Datamine), mine layout data (from AutoCAD), equipment data, and production schedules and organization.

The long-term mine production scheduling problem

Recognizing the complexity of coal mining management, e.g., the scarcity of financial resources and a variation in the quality of coal found in different sections of a mine, in this paper, we develop a mixed-binary programming model as an aid for generating mine production schedules in order to obtain coal of the desired quality and maximize the associated net present value. The model is based on the definition of the mine layout as a precedence network, with the nodes representing mining sections. A general solution methodology based on the Benders' decomposition of the model is developed. It exploits the special nature of the resulting subproblems in order to develop an effective solution procedure. Computational experience of this procedure, along with the results of its application to a mining case, are presented.

Oil Sands Slurry Flow in Flexible Pipe

Production cost and efficiency optimization for the Athabasca oil sands is a key to securing North America’s energy supply. Current oil sands production cost is about $13/bbl compared with $1.25/bbl for conventional crude oil. The effort to reduce production cost must focus on truck haulage because it contributes the dominant component of the production cost of about 26%. Toward this objective, hydraulic transportation has become a competitive means for materials handling. There is a desire to extend the hydraulic transport system to production faces using mobile train of flexible pipelines to optimize the system efficiency and cost. This flexible arrangement introduces a unique set of hydraulic transport problems, which must be addressed through rigorous modeling and analysis. This paper provides multiphase oil sand slurry models in flexible pipelines. New mathematical models are developed to characterize the multi-phase flow of oil sands slurry. The models combine the effects of dispersed particles and the carrier continuous phases. The coupled equations of each field are solved numerically for flexible pipe configuration. The models yield the productivity and deliverability of bitumen slurry between two mine facilities. The flexible arrangement allows modeling in elbow-type joint at different angles and in conventional linear pipelines, enabling adaptation of pipelines to various mine outlays. Numerical examples are presented to show the applicability of the new model and to ascertain optimum operational conditions of the flexible pipes in mine layouts.

Design of backfilled thin-seam coal pillars using earth pressure theory

In underground coal mining any increase in coal recovery rate is dependent on a decrease in pillar size. Backfilling is one way of reducing the required size of pillars and hence the volume of coal left underground. Therefore any comparisons made between a self-supported mine layout and backfill supported mine layout are based directly on pillar design. The most effective way to examine the effect of backfill on pillar support, and subsequently the rate of recovery, would be to incorporate the mechanisms of backfill support directly into the current design procedure for coal pillars. This paper presents a review of the mechanics of backfill support, a method of estimating the magnitude of that support based on earth pressure theory, and an example that incorporates backfill support into current coal pillar design.

A Computational Intelligent Algorithm for Surface Mine Layouts Optimization

Optimized surface mine layouts are used to extract mineable reserves with minimum waste under economic geological, geotechnical, and property boundary constraints. Surface mine design and optimization algorithms are limited in dealing with the random field properties of these layouts, resulting in suboptimal results. Database changes also require complete rerun of these algorithms, resulting in long CPU times with no allowance for incorporating operating strategies. In this study, the authors develop a computational intelligent (CI) algorithm to solve these problems. The CI algorithm combines the stochastic models of ore reserves and commodity prices to generate economic block and target values. The error back-propagation algorithm is used to train feed-forward neural networks for block pattern recognition and partitioning based on the target values. The CI algorithm is used to optimize Section SBHP 860001 of a surface mine layout, and the results are compared with that from the 2-D Lerchs-Grossmann’s algorithm.

A NEW DIMENSION TO STUDIES OF SPONTANEOUS COMBUSTION OF COAL

Spontaneous combustion of coal is a hazard frequently encountered in coal mining. It has been researched extensively but the actual mechanism by which it occurs is not completely understood. Under suitable conditions, the spontaneous combustion hazard manifests itself in all major aspects of coal mining, namely, underground coal mining, surface mining, stockpiling of coal at the pithead, power stations and ports, during sea-borne transport and stacking of reject material. In underground coal mining, the most difficult situation occurs when spontaneous combustion takes place in the presence of an inherently explosive atmosphere which may promote a local spontaneous combustion incident into an explosion hazard involving the entire mine. Such an incident at the Moura mine in Central Queensland resulted in greater pressure on mine operators for the safe management of spontaneous combustion in their underground coal mines than ever before. As not all coal mines are equally liable to spontaneous combustion due to the different propensities of different coals to self-oxidation, the risk assessment for spontaneous combustion is a primary requirement for the development of a spontaneous combustion management plan for a mine. Once the coal seam has been classified into various categories of spontaneous combustion risk, it is necessary to determine a fire ladder for the coal seam. This should be followed by detailed planning of the mine layout including the mine ventilation system and a spontaneous combustion monitoring program before devising a spontaneous combustion management plan as required by the Coal Mines Underground Regulations 1999. In this paper, a case history is presented which includes the development of a spontaneous combustion management plan for a high-risk coal seam in a greenfield site, from the risk assessment stage to the outbreak stage of a spontaneous combustion incident. It is concluded that the risk assessment, evaluation of the fire ladder, comprehensive monitoring by a tube bundle system and trending of carbon monoxide/oxygen deficiency ratio (Graham's ratio) and CO levels were the main elements in an effective spontaneous combustion control system for the mine.

Underground Planning at Stillwater Mining Company

As part of a new expansion effort, Stillwater Mining Company needed a tool for analyzing development and production scenarios in a new area of an underground platinum and palladium mine in Stillwater, Montana. We developed a large mixed-integer programming model that takes as input the planned mine layout, projected ore quality, and projected costs for basic mining activities, and produces as output a near-optimal schedule of activities that maximizes discounted ore revenue over a given planning horizon. We then used this model to evaluate various planning scenarios and make recommendations about development and production in this new area.

Underground Planning at Stillwater Mining Company

As part of a new expansion effort, Stillwater Mining Company needed a tool for analyzing development and production scenarios in a new area of an underground platinum and palladium mine in Stillwater, Montana. We developed a large mixed-integer programming model that takes as input the planned mine layout, projected ore quality, and projected costs for basic mining activities, and produces as output a near-optimal schedule of activities that maximizes discounted ore revenue over a given planning horizon. We then used this model to evaluate various planning scenarios and make recommendations about development and production in this new area.

Integrated seismic exploration for mine planning and profitability

First BreakVolume 18, Issue 8 p. 343-349 Integrated seismic exploration for mine planning and profitability D. Carpenter, D. CarpenterSearch for more papers by this authorC. Robson, C. RobsonSearch for more papers by this author D. Carpenter, D. CarpenterSearch for more papers by this authorC. Robson, C. RobsonSearch for more papers by this author First published: 24 December 2001 https://doi.org/10.1046/j.1365-2397.2000.00098.xCitations: 4 I. M. C. Geophysics Ltd, PO Box 18, Huthwaite, Sutton-in-Ashfield, Nottinghamshire, NG17 2NS, UK, Tel. +44 1623 441444; Fax: +44 1623 442072; E-mail: imcgeophysics@compuserve.com. Originally presented as paper P-594 at the 61st EAGE in Helsinki, Finland. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume18, Issue8August 2000Pages 343-349 RelatedInformation

Strike stabilizing pillars as a regional support strategy for ultra-deep gold mines

Strike stabilizing pillars are included in the mine layout of a number of deep South African gold mines as a means of providing regional support with the principal aim of controlling rockbursts. Large seismic events associated with stabilizing pillars can cause extensive damage to working areas. Mining-induced seismicity recorded at Western Deep Levels Limited has been analysed in an attempt to improve the design of stabilizing pillars, and thereby reduce their associated seismic hazard. This work revealed that the vast majority of stabilizing pillars, regardless of their dimensions and those of their adjacent stopes, will, at some time, give rise to seismic events of magnitude, M≥2. Contrary to expectations, this work strongly indicates that the rock mass in the near vicinity of the mined out areas does not behave in an elastic manner. Consequently, the currently employed design methodologies, based on elastic principles, should not provide the only criteria when designing strike stabilizing pillars.

Geotechnical classification of deep and ultra-deep Witwatersrand mining areas, South Africa

As depth of mining increases, so the production costs of the aurifereous Witwatersrand deposits are continuously increasing, with some mines already mining at depths exceeding 3500 m. Health and safety aspects are, simultaneously, gaining in importance. Therefore, in order to mine deep orebodies in existing mines, as well as to develop new mining ventures safely and efficiently, novel approaches, including mining strategies, layouts and support systems have to be adopted. Geological features largely control the deformation mechanisms associated with Witwatersrand orebodies. These features are grouped into two major categories: primary and secondary features. Both impact on the rockmass behaviour associated with the excavations, and contribute to the definition of geotechnical areas. Primary geological features are defined by the various rock types, orebody geometry, and the frequency and mineralogical characteristics of sedimentary structures (e.g. various kinds of bedding planes and lithological boundaries). The primary features also control rock engineering properties, closure rates, attitude and frequency of mining-induced stress fracturing, and planes may be reactivated during seismic events. Secondary geological features are faults, dykes and veins/joints, and associated metamorphism. These cause stability problems and are often associated with seismic events. Compositional and textural characteristics of these features, and their controls on the rockmass behaviour, are ill-defined. Primary and secondary geological characteristics also play an important role in identifying the appropriate mining strategy, layout and support. Geological features can be predicted into deep unmined areas, and therefore contribute to the safest and most efficient extraction of the orebody. Witwatersrand orebodies are mined in complex geological environments, with the rockmass behaviour differing from one orebody to the other. This is approached by employing a new methodology that attempts to quantify the problems encountered when mining the major Witwatersrand orebodies.

Integrated seismicity around deep-level stopes in South Africa

Stresses acting on a rock mass, elastic deformations of the area mined out, the amount and method of mining, geological features and rock properties are known to influence mining induced seismicity. The effect of stress and mining method on seismicity can be measured by the ratio ( γ E ) of cumulative seismic moment to the product of rigidity and volume of elastic convergence. The seismic moment has a logarithmic nature and can be dominated by the few largest events. To reduce this effect we use a supplementary parameter that is empirically related to the incidence of rockburst fatalities ( γ R ). As larger events are less hazardous per unit of seismic moment, γ R is less controlled by the largest seismic events. The parameters γ E and γ R were estimated for thirty seismogenic areas selected on the basis of the mining layouts, seismic locations and local geology from three deep-level mines in the Carletonville mining district. It was found that γ E and γ R were far from constant. The ratio of the values of the 80 percentile to the 20 percentile was about five for γ E and γ R . The scatter in values of γ E and γ R exceeded the reduction in volume of closure and expected seismicity by the introduction of regional stability pillars. As these pillars were introduced to reduce seismicity by a factor five or less, there is scope to improve mine layout design by using seismicity to characterize the local potential for seismicity.