Optimum life of mine: declining production case

Conclusions By considering the mine to be depleted at a non-constant rate a considerable change in the mine life has been found. One can next consider a sensitivity analysis to determine which changes in which parameter are the more influential on the mine. Four computer programs were written in Fortran IV to use in this analysis and listings are available from the author. They are in interactive mode designed to be used for educational purposes.     

Astrata control system and its application in West German coal mining

Summary Astrata control system has been developed to improve mine planning and design in deep coal mines in West Germany, where redistributed stresses from longwall workings in weak strata create difficult support problems. The system involves theoretical, laboratory and underground observations and studies of strata and support performance. Examples of the system covered in detail include planning the position and support of a cross-cut; improving a face layout; planning a gateroad; planning strata bolting and planning longwall face layouts.     

A physical model of an underground coal mine prototype

Conclusions A physical model simulated qualitative ground movement above a retreating longwall face in a shallow coal mine with considerable accuracy, after modification to allow for scale effects. It is considered that in prototype geometries such as mines where strata deformation involves rock fracture, the use of physical models may have advantages over other types of model.     

Effects of stopping leakage on coal mine ventilation systems

Summary This paper deals with the effects of air leakage from intake to return airways through a series of stoppings on the analysis of coal mine ventilation. The mathematical model which assumes continuous leakage along adjoining intake and return airways is reviewed, and a new mathematical approach is presented based upon the concentrated leakage through individual stoppings. The procedure incorporating the new method in the analysis of coal mine ventilation networks is also discussed.     

Statistical interpretation of gate roadways deformation data in the UK

Summary The uniformity of measurements of deformation in underground coal mine roadways is discussed. Hence the validity of using such results for predicting the likely behaviour of similar workings is examined. It is further attempted to isolate those geological and mining parameters which influence closure. These results are compared with those from West Germany and France.     

Effect of the form of data on the quality of mine tremors hazard forecasting using neural networks

During hard coal mining operations conducted under conditions of rockburst hazard, one of the most important preventive measures can be the prediction of occurrence time and location of the strong seismic mine tremors of energy E _s ⩾ 10⁴ J. This is a very difficult task and the way it is being currently performed appears to be unsatisfactory. Therefore, attempts have been made to use neural networks, specifically trained for this application. The paper presents an approach for determining an influence of the type and shape of the input data on the efficiency of such a prediction. The considerations are based on a selected example of the seismic activity recorded during longwall mining operations conducted in one of the Polish mines.     

Heuristic approaches for mine planning and production scheduling

Summary Traditional methods and opimization methods for mine planning and production scheduling have failed to provide easy to use tools that yield improved results. Two new approaches, each combining the best of the traditional and the optimization, are described.     

Analysis of subsidence caused by underground mining

Summary Some aspects of subsidence caused by longwall coal mining are analysed using the finite element method. Results of the analysis are compared with a true mine panel, where measurements on subsidence were available. Rock deformations in the overburden were modelled by using an elasto-plastic constitutive model. The study indicates that the shape of the subsidence profile can be predicted reasonably well by using nonlinear finite element analysis.     

Assessment of stress around mine workings at the time of rockburst occurrence

This article deals with a specific rockburst case in the ?SM Mine in the Ostrava-Karviná Coalfield (OKC), Czech Republic. Determination of the magnitude of acting stress is based on the constant weight of the overlying rocks. The rule that the force of stress relief of a mined-out space is equal to the force of additional load in the surrounding unmined area holds true. The magnitude of stress relief is influenced considerably by whether the total thickness of strong overlying layers is disturbed. The state of complete failure of overlying layers is assessed on the basis of undermined surface subsidence measurement. In the case considered, multiple seams were mined; thus, stress transfer to overlying as well as underlying layers is dealt with. In the individual stages of the calculation of acting stresses, the basic rule that the constant weight on the whole affected area, corresponding to the whole roof, was checked. Stress is determined at the time of rockburst occurrence. The maximum magnitude of acting stress around the mine workings reaches up to approximately 100 MPa, which is five times the original geostatic pressure.     

Fuzzy influence function method for calculating mine subsidence in a horizontal seam

Summary The fuzzy influence function method takes account of the effect of the rock mass around the edges of a panel on the surface subsidence. Unlike conventional influence functions, the shape and value of the fuzzy influence function varies with both the position of points calculated on the surface and the position of elements integrated in the extracted area underground. Consequently, the results obtained by using the fuzzy influence function method can automatically give rise to a shift of the inflection point towards the goaf and asymmetry in shape. The accuracy of the calculation is also improved. Case-history examples of mining subsidence engineering show good agreement between the results from geodesic measurements and those calculated from the fuzzy influence function method. The programs for back-analysis of parameters can approach satisfactory results of optimization.     

Stresses and displacements due to underground mining using a finite element procedure

Summary A two dimensional finite element procedure is applied to simulate a coal mining excavation sequence. A procedure with linear solution steps is developed and applied to an idealized mountain cross-section with exceptionally thick coal seams and large dip angle. The results provide information on pillar pressure, floor and roof stability, displacement characteristics and surface subsidence.The results presented here were obtained in the course of research sponsored by the Department of Energy, Mines and Resources, Grant No. 69-2570.     

Nitrogen and carbon dioxide occurrence in UK coal seams

Conclusions Some bituminous coals, mostly of high volatile rank, sampled from various coalfields contained on average 0.5 m³ t^–1 nitrogen and 0.13 m³ t^–1.Nitrogen is released more readily than methane during coal winning but the volumes of nitrogen released are small compared with ventilation quantities and are only likely to be of significance for detailed oxygen deficiency studies.     

Support capacity and roof behaviour at longwall faces with shield supports

Summary Field investigations on seven U.S. longwall coal faces were carried out to examine the behaviour and interaction of roof, floor and support on longwall faces equipped with hydraulic powered supports. The most important factor in determining face stability was found to be periodic weighting and an empirical design equation was developed for support capacity. The interaction of various elements in the face system is examined and discussed.     

Use of rock classification to estimate roof caving span in oblong workings

Summary Indian coal measures have widely varying caving characteristics. The maximum roof span of a longwall or depillaring panel at the time of nether roof collapse is shown to have a direct relation withRQD from a study of 12 case histories. A similar relation between maximum unsupported span of openings and rock mass quality as defined by theQ-system was also demonstrated. A simple nomogram is presented to predict the face advance required to cause roof collapse when theRQD or rock mass quality is known.     

准格尔煤田不连沟矿井构造特征及其对煤矿生产的影响

准格尔煤田位于鄂尔多斯盆地伊盟隆起和晋西褶曲带的转折部位,煤田内的矿井构造样式多样,而且矿井生产揭露前后构造复杂程度发生了重大变化。以不连沟矿井地质勘查和矿井揭露的褶皱、断层、岩溶陷落柱、火成岩侵入体等地质构造为主要研究对象,通过数理统计方法对矿井内的构造发育特征进行了定量或半定量评价,分析不同地质构造的形成机制、演化背景及矿井构造复杂程度变化的主要原因,统计分析不同类型地质构造对矿井采掘生产的影响,总结矿井地质构造探查经验,提出适应于该区的构造探查思路。结果表明：不连沟煤矿构造样式多样,构造发育的分区特征明显,构造组合具有耦合性;矿井中部的弧形坡折带及波状褶皱形成开始于加里东构造运动,属于黄河断裂和呼-清断裂的伴生构造;区内走向EW （或近EW向）和NW断层组合是鄂尔多斯盆地印支期S—N向挤压应力和燕山期NW—SE向挤压应力共同作用的结果。各类地质构造制约着矿井采区部署、巷道掘进、工作面回采速度,造成大量资源损失,给矿井防治水带来巨大挑战。针对类似研究区的复杂矿区,建议采用三维地震勘探扫面,井下槽波、电法勘探靶区圈定,定向钻验证的“物探、钻探,地面、井下”相结合的综合探查方案。     

Multilevel optimization of surface coal mine truck and shovel fleets

Summary Optimization algorithms are developed to improve the selection of truck and shovel fleets for suface mine operations. These are based on performance estimation models developed by Fluor Utah (1977) and graphical display algorithms and other software within the SEAMPLAN system developed at Montana State University. The advantages and disadvantages of the method are considered.     

Computer aided design and strata control

Summary Research into strata control has been pursued at Cerchar for the last 20 years, and has led to the definition of rules for the siting of new mine workings. These rules are drawn up as a function of the volume of influence which is exerted by existing workings. To facilitate their application by the coal producer, a computer-aided design system for steep-seam faces has been developed on a minicomputer. The main features of the interactions which occur within the volume of influence of such faces are restated and the system which has been developed for design is described, with particular emphasis on the design stages which involved graphic systems and data base management.     

环境同位素示踪技术在矿井水防治中的应用

环境同位素示踪技术是近几年新发展起来的一项新技术。采用环境同位素作为天然示踪剂可以标识矿井水分布、运移和补给规律,为矿井水害的防治提供直接依据,实例表明,采用该技术具有快捷、准确以及易于推广应用等特点     

Hydrogeochemical characteristics of acid mine drainage and water pollution at Makum Coalfield,India

Acid mine drainage (AMD) is one of the severe environmental problems that coal mines are facing. Generation of AMD in the northeastern part of India due to the coal mining activities has long been reported. However detailed geochemical characterization of AMD and its impact on water quality of various creeks, river and groundwater in the area has never been reported. Coal and coal measure rocks in the study area show finely disseminated pyrite crystals. Secondary solid phases, resulted due to oxidation of pyrite, occur on the surface of coal, and are mainly consisting of hydrated sulphate complexes of Fe and Mg (copiapite group of minerals). The direct mine discharges are highly acidic (up to pH 2.3) to alkaline (up to pH 7.6) in nature with high concentration of SO₄²⁻. Acidic discharges are highly enriched with Fe, Al, Mn, Ni, Pb and Cd, while Cr, Cu, Zn and Co are below their maximum permissible limit in most mine discharges. Creeks that carrying the direct mine discharges are highly contaminated; whereas major rivers are not much impacted by AMD. Ground water close to the collieries and AMD affected creeks are highly contaminated by Mn, Fe and Pb. Through geochemical modeling, it is inferred that jarosite is stable at pH less than 2.5, schwertmannite at pH less than 4.5, ferrihydrite above 5.8 and goethite is stable over wide range of pH, from highly acidic to alkaline condition.