Paper: Technologies for Decreasing Mining Losses

txt: Environmental and Climate Technologies _________________________________________________________________________________________________2013 / 11 41 doi: 10.2478/rtuect-2013-0006 Technologies for Decreasing Mining Losses Ingo Valgma , Vivika Väizene1 , Margit Kolats1 Tallinn University of Technology Abstract - In case of stratified deposits like oil shale deposit in Estonia, mining losses depend on mining technologies. Current research focuses on extraction and separation possibilities of mineral resources. Selective mining, selective crushing and separation tests have been performed, showing possibilities of decreasing mining losses. Rock crushing and screening process simulations were used for optimizing rock fractions. In addition mine backfilling, fine separation, and optimized drilling and blasting have been analyzed. All tested methods show potential and depend on mineral usage. Usage in addition depends on the utilization technology. The questions like stability of the material flow and influences of the quality fluctuations to the final yield are raised. Keywords – oil shale, losses, mining, extraction. I. INTRODUCTION In case of stratified deposits like oil shale deposit in Estonia, mining losses depend on mining technologies. Stratified deposits are being developed from lower bedding depth to deeper and more complicated conditions [23]. Continuously the environmental or social restrictions require increasing coefficients that increase mineral losses [20]. This could be limited with the help of technological development [34,13, 36]. During the period starting from 1916 many technologies have been used and tested [31]. Currently the market economy is the main driving force for choosing technologies. This causes short term choices and works against sustainability. Current research focuses on extraction and separation possibilities of oil shale. Selective mining, selective crushing and separation tests have been performed, showing possibilities of decreasing mining losses. Rock crushing and screening process simulations were used for optimizing fractions. In addition mine backfilling, fine separation of oil shale, and optimized drilling and blasting have been analyzed. All tested methods show potential and depend on mineral usage [37]. Usage also depends on the utilization technology. Questions like stability of the material flow and influences of the quality fluctuations to the final yield are raised. Tonnage, calorific value and size distribution of the product form the quality indicators [43]. Avoiding losses in any of these processes decreases mining losses and has a positive effect on resource usage and sustainability. In addition, decreasing losses increases the amount of resource and sustainability of energy supply for the country [30, 32]. If optimized technology allows maintaining required productivity, it could be applied, even if fitting into the existing technological structure is taking longer than technically available [33, 35, 8]. The aim of the current study is to clarify what technical solutions could be applied for decreasing oil shale mining related losses. II.ANALYSES AND TESTS A. Selective mining Selective extraction of oil shale seam was analyzed to understand following methods: 1. Cutting with bulldozer and excavator rippers 2. Cutting with surface miners 3. Cutting with longwall miners 4. Cutting with shortwall miners. a) Cutting with rippers Selective extraction of the oil shale seam can be done by a bulldozer ripper or hydraulic excavator ripper. Ripping is a low-selective technology [42]. In deeper surface mining areas, 100 tonnes class bulldozers were used and in more weathered areas or partial ripping zones, the 60 tonne class was used. One disadvantage of bulldozer ripping is excessive crushing of oil shale by heavy bulldozers with crawlers [18]. b) Cutting with surface miners Tests with surface miners Vermeer T1255 and Wirtgen 2500 SM were carried out. The tests were followed after longer period tests with smaller class surface miners during the last 25 years. Tests have been performed with different oil shale and limestone layers. Surface miners are considered as BAT (Best Available Technology) for surface oil shale mining extraction [12, 42, 18, 15, 5]. c) Cutting with longwall miners The planning and testing has been done for longwall mining possibilities. Shearers were used and tested for 30 years in five oil shale mines in Estonia [1]. Longwall technology has also been chosen as one of the alternatives for phosphate rock mining [41]. Technologically, this technological solution has improved compared with initial possibilities. Since the hydraulic support system was limiting the height of the longwall face (1,5 m) and the power of the shearers was relatively low (210 kW) the losses have been 50% in longwall section. Today’s sharers utilize power in the range of 2200 kW, which is 10 times higher than in the tested units. Since the productivity (equal to income) could be increased, longwall technology is one of the possibilities for lowering losses. In case of removing protective side pillars between longwall section, rough estimation shows, that losses could be lowered down to 5% taking into account the geological dislocations and disfollowing the exact horizontal plane of the oil shale seam. The main obstacle of longwall shearing Brought to you by | Tallinn Technical Authenticated | 193.40.249.178 Download Date | 10/17/13 10:07 AM Environmental and Climate Technologies 2013 / 11_________________________________________________________________________________________________ 42 technology is solving environmental and social questions, regarding subsiding the ground and accepting certain areas where such subsiding could be allowed. In comparison to the surface mining stripping in the open cast mining areas, longwall mining could be considered as a technology which causes less impact to the landscape. The ground would be lowered by up to 70% of the created space. That makes 2 meters. In open casts, even the fluctuations in the leveled overburden spoil could be 5 meters. In trench or ditches areas, the level fluctuations are up to 40 meters. This makes longwall mining the most sustainable mining method for oil shale. d) Cutting with shortwall miners Evaluations of breakability have been made with roadheaders F2 and 4PP-3. As a recommendation, a doubledrum road header was proposed. Currently the power of the machines has increased and pick properties allow cutting harder rock. It is proposed, that both longitudinal or transverse head continuous miners (roadheaders) could be used for cutting oil shale [12]. The selectivity option is directly related to the waste material handling and should be tested in the mine [11]. Shortwall miner utilization could be the solution for making development entrances, drifts and rooms for mining. In case of satisfactory cutting performance, it could be used for extracting oil shale in production sections as well. The tests have shown, that shortwall mining is a promising technology and requires, as with longwall mining, surface miner mining and axle bucket crushing changes in some operations and processes in mining technology. Shortwall mining requires fast roof supporting technology. The supporting could be in addition in some extent easer because of lower possible fragmentation of rock caused by absence of blasting in the mine. B. Selective crushing For selective crushing, the following methods were tested: 1. crushing in a drum (Bradford drum) with help of rock falling impact and hammer crusher inside the drum; 2. impact crusher in underground sections as first stage crusher or impact crusher for aggregate production from oil shale waste rock; 3. axle crusher buckets with cutting and skimming process. An impact crusher has been used in underground sections as a first stage crusher and for aggregate production from oil shale waste rock that is limestone [27]. The purpose of underground crushing is to reduce ROM (run of mine) size to the required size of up to 300 mm for transporting it on belt conveyors to the surface. C. Separation Separation tests have been performed by jigging and cycloning. The purpose was to find out the percentage of the fine material that could be separated. Jigging tests have shown relatively good results allowing separating initially mixed material into five different fractions. The calorific value of best fraction is highest and the limestone fraction in opposition should be considered as the ready selected material for limestone aggregate. Up to now the main focus has been mechanical experimenting with jig. The main obstacle of the technology could be achieving required productivity. It is similar to the filter press technology where the productivity of the single unit could be low. On the other hand, if the production line could be completed with different stages, the required productivity could also be to some extent lower. To decrease required machine productivity for the same output, drum crushing or axle crushing could be used prior to the jigging. Cycloning has shown that the calorific value of cycloned and non- cycloned fine material has no remarkable difference. Since cycloning could be done on many variations, the initial test could be considered as failed because of short time and no variations. These tests should be continued, preferably with apilot unit or laboratory units at first. D. Rock crushing For crushing, the following options have been analysed: 1. Crushing with sizers 2. Crushing with impact crushers 3. Crushing with double drum crushers 4. Crushing with drum crusher 5. Crushing with jaw crusher. Crushing process simulations were used to evaluate the distribution curves of the final product. The necessary data for this purpose is bulk density of material and the maximum size of the particles going for crushing. In order to get optimal results on certain cases, crushing units, crushers and mobile crushers can be added to the scheme. This gives extra value in lowering engineering costs, on experimenting with different devices and on further changes [19, 45]. As an example, material data for thesimulation program has been:  Input material < 1000 mm  Solid density 1,84 t/m3  Crushability 85% - which is the maximum  Productivity 1000 t/h  Gravel 31% - does not influence the results (Fig. 1.). The value of abrasiveness has been between 0,1…1500 g/t, calculations show that this does not affect the simulation results. Neither does moisture. The crusher output cavity is set on 180mm which means that the maximum size of the outcoming particle is 200mm. The workload of the impactor crusher is 97% of the maximum capacity. After crushing, the feed moves to the roller screen, where the feed flows into three classes:  0…25 mm 22,8%  12…107 mm 55,2% - which include 11% 12…25 mm (Fig.2.)  107…200 mm 22% . It can be detected that the fines part is 28,9%. Brought to you by | Tallinn Technical Authenticated | 193.40.249.178 Download Date | 10/17/13 10:07 AM Environmental and Climate Technologies _________________________________________________________________________________________________2013 / 11 43 Fig. 1. Material data insertion window Fig. 2. Flow data Fines are added on the secondary crushing/particle size is 107...200 mm. Calculations have shown that in this way 5% of fines are added. At the present moment the best crushing option in making the minimum fines is crushing with the sizer. Experiments show that the minimum in generating fines is achieved when the rotating speed of sizer was 175 rpm. In slow rotation the generation was 11,8% and fast rotation gave 6,5% of fines (Fig.3). As experiments show, it is possible to decrease the fines generation which mostly is considered to be waste. Each simulation manufacturer focuses on separation methods or some part in the separation process. When it comes to crushers, then simulations are also manufacturer based and reflect types and models, what the company offers [7, 4]. Newer products are introduced in the simulation programmes later. In case of the roll crusher for example, the characteristics and behaviours are still added to the programme. Sizers are even more complex, because they have been used only a few years and therefore are relatively new products among crushers. In Estonia there are a lot of questions concerning the fines in the crushing process. Fig. 1. Experiments resulted in fines generation of 2,2% [10] E. screening Two basic screening solutions have been analysed in addition to the traditional vibration screening: 1. Screening in drum screen 2. Screening on rotary screen 3. Screening on roller screen. F. Mine backfilling The tests contained testing of mixes properties of the backfill material, testing of backfilling technology and analyzing backfilling material flows. The main hypotheses are that backfilling reduces mining losses and the amount of waste on the ground surface [27]. In addition it increases land stability [12]. Stability issues have been developed in sense of information availability. Mapping, special information systems and seismological methods allow one to detect any collapses which have occured [21, 25]. G. Fine separation Fine separation tests were carried out with CDE equipment and with jigging equipment. The aim of the fine separation test is to separate fines from pulp before they reach sedimentation pond and to take it into use as a product. III. RESULTS AND DISCUSSION A. Selective mining a) Cutting with rippers In Ubja oil shale open cast, the productivity of oil shale hydraulic ripping was nearly 600 m3/h. At the Ubja open cast, overall oil shale losses are 0% based on the Environmental Register. Bulldozer ripping is considered as semi-selective ripping where seam losses make 12% in comparison to 5% with surface miners [42]. The first problem of ripping technology has been power of ripping machines. Before 100 tonnes class bulldozers were applied, the low ripping power was one of the main concerns. Excavator ripping is in similar stage like bulldozer ripping has been in its beginning stage. The power of the excavator ripper is not satisfactory to reach required productivity. Excavator ripping does not solve the losses question because of the principle of vertical movement. Brought to you by | Tallinn Technical Authenticated | 193.40.249.178 Download Date | 10/17/13 10:07 AM Environmental and Climate Technologies 2013 / 11_________________________________________________________________________________________________ 44 Excavator ripping could be considered in low bedding areas, where drilling and blasting is prohibited, the oil shale seam is weathered meaning weaker bonds between layers. A bulldozer ripper, therefore could be used as low selective miner, but it is limited by availability of keeping losses down. The main problem is limestone and oil shale pieces and lumps that contain both material and could not be separated by the ripper. If needed, one of the solutions could be skimming with axle crushers. b) Cutting with surface miners It was found that extracting with a high selective surface miner is the main possibility of decreasing losses in case of surface mining. The main obstacle for using such technology is the partly unsolved overburden stripping technology. In the future, combined methods should be considered like high selective cutting plus selective axle crushing for aggregate separation. Mining with surface miner Wirtgen 2500 SM helps to reduce losses and improve calorific value of oil shale. It is possible to mine limestone and oil shale seams separately with higher accuracy than rippers (2-7 cm) with deviations about one centimetre [42]. Losses can be decreased from 12 percent to 5 percent compared to ripping [18]. Based on practical data, the surface miner enables to increase the output of oil shale up to 1 tonne per square meter. The oil yield increases 30%, reaching up to 1 barrel per tonne of oil shale during the oil shale retorting, because of better quality, meaning higher calorific value of the material that is sent to the retorts [42]. c) Cutting with longwall miners It was found that distribution of required large particles of oil shale is possible with longwall shearers. The practice with longwall shearers shows that the subject for cutting is oil shale and the larger size is distributed to the limestone fraction [1]. This is due to the hardness difference of the rocks. Longwall mining could decrease horizontal losses by 20 to 40%. d) Cutting with shortwall miners One of the main advantages that a shortwall miner could present are the possibility of avoiding weakening pillars in the mine by blasting [20]. This in addition could give the possibility to decrease pillar size and to decrease losses left to the pillars. Pillar losses that are caused by pillars with cross section area of 16 to 49 square meters could be decreased therefore by 16 to 28% with avoidance of the 0,3 zone by sides of the pillars. The pillas strength and stability of the ground are directly related but have the opposite influence on sustainability. In case of backfilling this dilemma could be solved [22]. In some areas also smooth and directed subsidence could be solution. B. Selective crushing The underground crushing process where ROM (run of mine) size is reduced to the required size up to 300 mm has no direct influence on the percentage of losses. Nevertheless, ROM size distribution is influenced by impact crushing and fines are produced. In case of oil production with vertical generators, fines and small classes of oil shale are considered as waste, if no other uses are found, like cement, electricity or oil production with SHC technology. Selective crushing is important both for cleaning and sizing oil shale and cleaning and sizing limestone. Therefore selective crushing or selective mining methods are recommended [27]. C. Rock crushing a) Crushing with sizers One of the options could be using slow rotating or optimized rotating sizer for oil shale ROM crushing. According to the recommendations of crusher producers, all crusher types are suitable for crushing oil shale [25]. In relation to the moisture content, jaw crusher and gyratory crushers are unsuitable, requiring relatively dry material (

Oil Shale mining-related research in Estonia

txt: Oil Shale, 2009, Vol. 26, No. 4, pp. 445–450 ISSN 0208-189X doi: 10.3176/oil.2009.4.01 © 2009 Estonian Academy Publishers EDITOR’S PAGE OIL SHALE MINING-RELATED RESEARCH IN ESTONIA Finally the long-announced changes arrived, caused by environmental, geological and technological changes in oil shale mining sector. In addition, the biggest change has occurred with alteration of professionals’ generation. In most of the countries, the institutions dealing with mining are facing difficult questions – to continue or not to continue, and if, then how. Research, development and teaching work are facing a low at the moment. The biggest section in oil shale business in which saving and effectiveness could be achieved is the mining sector. It includes social and environmental restrictions in deposits, losses in pillars and separation of products and waste rock. Losses are closely related to backfilling and waste rock usage. Much smaller sections include production of oil, electricity and chemicals in which most of the research and development is performed today. Efficiency of oil shale usage depends manly on mining technology. 446 Editor’s Page Current urgent topics for investigating, testing and developing of oil shale mining related questions are backfilling, mechanical extracting of shale and digital modelling of mining processes. Estonian oil shale mining industry with its 90 years of history has been a test polygon for equipment manufacturers, geologists and mining engineers from Germany, Soviet Union, Finland and Sweden. These are the reasons why Estonia has recently hosted in average one international mining-related conference per year and is going to host the most important and highest level of the conferences – Annual General Meeting of the Society of Mining Professors “Innovation in Mining” (SOMP AGM 2010, http://mi.ttu.ee/somp2010). Mining research concerning Estonian oil shale deposits Several mining-related factors, such as changes in environment, underground conditions, landscape and property, tend to awoke public resistance. In order to create sustainable mining conditions, research on the natural environment and experiments conducted in mines and mined areas are required. Together with physical experiments, computer modelling is a widespread method in mining engineering. The principal task of modelling is to choose criteria and constraints satisfying all involved parties, as well as ways of presenting. In reaction to this, various restrictions for mining (mainly environmental ones) are created. In most cases, their argumentation is onesided, often subjective. As a result, it is not possible to exploit a large part of deposits due to environmental restrictions, but also due to expiration of evaluation criteria of the supplies of resources. Part of the problems is caused by miners that do not apply environmentally friendly mining technologies. Mining environment is understood as the entity including resources (deposits and groundwater), land (agricultural and housing land), engineering and technology. Research has shown that ground and landscapes changed by mining can afterwards be of better quality than before. If reclaiming is planned skilfully, the soil, landforms, forest, water bodies and agricultural land can be more valuable than before mining. All this is the basis for developing acceptable, environmentally friendly mining. Acceptable mining requires engineering research concerning both natural and technogenic environment, e.g. modelling and pilot projects. As such research is voluminous, computer modelling has become the principal tool in solving problems related to all sorts of developments, technologies and effects. The key issue is defining criteria and restrictions that satisfy all the involved parties. Creating models and estimation criteria requires miningrelated expertise and a database acquired from measurements, experimenting and laboratory testing. Modelling is followed by laboratory and industrial experiments, which require profound know-how. The experiments include e.g. chronometry of technological productivity, geometric and geological measurements, and measurements of rock quality. The parties that compose mining plans, development plans and estimations of environmental effects Editor’s Page 447 have acquired planning and modelling software for various purposes, which causes some problems: the geological database requires skilful treatment; data exist in several geodetic coordinate systems and include partly obsolete stratigraphic terminology. Unfitting coordinate systems disturb the usage of cross-use of spatial data in various geoinformation databases (digital maps, border files, land registers, building registers, databases of technological networks of enterprises, etc.). This creates further problems related to mined areas. Most environmental restrictions, which have to be taken into account in mining and building, are not based on real measurements. Usually the restrictions are two-dimensional and do not take into account the structures of the geological environment. Such vagueness does not support precise engineering calculations or modelling. Basic modelling systems that are designed in developed mining countries are principally meant for deep deposits. However, in Estonia there are blanket deposits, which cause wider environmental effect of mining. Because of that, imported systems have to be adapted. Mining is possible in any circumstances, provided that sustainable mining environment has been created. In other words, with the proper choice of mining technology, the effect of mining has been damped below the level that the nature and man can tolerate. The methodology and criteria for planning, designing, modelling and accepting of sustainable mining environment will provide the basis for mineral raw material that the economy requires, both in the near and far future. The principal direction of developing mining technology is filling the mined area. This provides control over majority of environmental effects. For instance, filling the workings decreases the loss of resources and land subsidence, and at the same time provides usage for stockpiling. Filling the berms of surface mine decreases dewatering; harmless waste can be used for filling open mines and in this manner offer new building land. Local land subsidence related to mining may extend also to technological networks. It is possible to find out deformation parameters by geodetic monitoring. Taking these parameters into account enables to model further the extent and effect of the deformation. Modelling, including digital planning, is aimed at gaining and creating the following: mining indicators needed for making decisions, future scenarios of mining oil shale and building material, support for development planning at state and regional level, technological solutions that take into account all possible environmental effects and social reactions, new output: project solutions, theme maps, inquiries, zoning, evaluations of crises or risks, optimal methodology for gaining, storing and using information, having in mine requirements for various purposes and levels, more effective usage of geological, technological and spatial information, additional functionality of the database. The optimal solution is obtained by modelling. The most general but also dominant criteria are: minimal effect on man and nature, minimal amount of 448 Editor’s Page residual and waste, maximal economic profit, also in other fields not only in the mining industry. The problem includes several criteria, and its solving requires both theoretical and computational solutions. Principal methods are related to introducing sensors, measuring equipment and mining condition experiment, matching structures of various data and modelling based on them. The methods are: mapping the modelling criteria, indicators and processes of the mined areas; experimenting the possibilities of application, compatibility and results of mining software; applying laboratory experiments and fieldwork in modelling; creating models for blanket deposits (methodology in modelling MGIS, i.e. mining geoinformation system, models of new mines, changes in ground conditions, environment (modelling and analysis of groundwater dynamics, effects of dust, noise, etc.), geotechnological models in mined areas); applying seismological methods for developing theory for collapse risk, analysis methods for creating spatial models from geodetic spatial information, studies on material properties for developing theory for criteria for rock breakage, dendrochronologic studies for monitoring changes caused by collapses and changes in the water regime. As a result, conditions for creating mining environment satisfying all involved parties (industry, state, public, decision makers) will be developed, applicable for any deposit of any resource. A system of criteria of evaluating the mining environment will be designed. This research provides for mining science a new level of digital modelling of blanket deposits, basing on long-term experiments and modern digital planning. The research results will be applied in compilation of the state development plan, planning mined areas, as well as in teaching and science. The results are relevant principally for users of land and ground (builders, geologists, hydrogeologists, hydrologists, mining engineers and reclaimers). The results provide better understanding between the public and the miners, and further a basis for well-argumented communication and promotion for economy in the manner that satisfies both parties. In recent years, there has been a world-wide initiative for research, creating the concept of sustainable mining, using relevant indicators and making decisions based on them. MMSD (Mining, Minerals, and Sustainable Development), SDIMI (Sustainable Development Indicators for the Minerals Industry) and other international networks emphasize the need for creation of a concept for regional sustainable mining, relevant for local conditions. At the same time, modelling systems are being built and usage of non-traditional fuels is being started. About three decades ago oil-shale mines of the former USSR including Estonia did not use the progressive mining methods with continuous miner, which are most suitable for the case of high-strength limestone layers in oilshale bed. Therefore, oil shale mining with blasting has been used as a basic mining method in Estonian minefields up to now while continuous miner was tested for roadway driving only. As for cutting, the installed power of Editor’s Page 449 coal shearers and continuous miners has increased enormously since the original work. The actual state of the market has changed, and a wide range of powerful mining equipment from well-known manufacturers like DOSCO, EIMCO, EICKHOFF, etc. is available now. Estonia has 30 years of experience in cutting with longwall shearers which were not capable of cutting hardest limestone layer inside of the seam. Tests with road headers have been carried out in the 1970s. Additionally Wirtgen surface miners have been tested (SM2100 and SM2600) for two years as well as SM2200 and Man Tackraf surface miner, and currently the testing of Wirtgen surface miner SM2500 for high selective mining in an open cast mine is being performed. The main field to be developed in addition to mine backfilling is mechanical extraction of oil shale. Potentially this allows increasing oil yield, decreasing CO2 pollution, decreasing ash amount, decreasing oil shale losses, avoiding vibration caused by blasting, avoiding ground surface subsidence (in the case of longwall mining), increasing drifting and extracting productivity compared with current room and pillar mining, increasing safety of mining operations. The final aim of the research is to use BAT (best available technology) for underground mining in areas with arduous conditions of coal and oil-shale deposits. The main problems to be solved are: selective cutting of oil shale (15 MPa) and hard limestone (up to 100 MPa), roof support at the face, stability of the main roof, roof bolting, pillar parameters, backfilling with rock or residues (ash) from oil production, water stopping and pumping in problematic environment (30 m3 /t expected). Currently room and pillar mining with drill and blast technology is used underground. Supporting is done with bolts. Mining production is in total around 14 Mt/y, including 7 Mt/y underground. Total raw material amount underground is 12 Mt/y. Tests are made for opening new mines, with total production 15 Mt/y. Continuous miners keep playing a major role in the underground industry in over fourteen countries worldwide. Estonia’s oil-shale industry is at the beginning of introducing modern fully mechanized continuous miner systems, which could increase productivity and safety in the underground mines. A longitudinal cutting head-type miner was first introduced in the former Soviet Union by modifying the Hungarian F2 roadheaders and in the 1970s in Estonia by modifying the Russian coal roadheader 4PP-3. Evaluation of breakability was performed by a method developed by A. A. Skotchinsky Institute of Mining Engineering (St Petersburg, Russia). For this purpose over a hundred samples produced by cutting of oil shale and limestone, as well as taken in mines by mechanical cutting of oil shale were analysed. Evaluations were made for using coal-mining equipment for mining oil shale. Comparative evaluations were made by the experimental cutting of oil shale in both directions – along and across the bedding, including also mining-scale experiments with cutting heads rotating round horizontal 450 Editor’s Page (transverse heads) and vertical axes (longitudinal heads). In both cases the efficiency was estimated by power requirement for cutting. The feasibility was shown by breaking oil shale in direction of cutting across the bedding by using cutting drums on horizontal axis of rotation. The research also evidenced that the existing coal shearers proved low endurance for mining oil shale. Therefore, there arose the problem of developing special types of shearers for mining oil shale or modifying the existing coal shearers. It was further stated that the better pick penetration of the longitudinal machines allows excavation of harder strata at higher rates with lower pick consumption for an equivalent-sized transverse machine. It was reported that with the longitudinal cutting heads the dust forming per unit of time decreases due to smaller peripheral speed. The change in the magnitude of the resultant boom force reaction during a transition from arcing to lifting is relatively high for the transverse heads, depending on cutting head design. Specific energy for cutting across the bedding with longitudinal heads is 1.3–1.35 times lower which practically corresponds to the change of the factor of stratification. These are the questions waiting for answers in the near future for effective oil shale extraction in Estonia and in similar mining conditions. In spite of current economic problems, still everything begins with mining. Ingo VALGMA Head of Department of Mining of Tallinn University of Technology, Head of Estonian Mining Society, President of the Society of Mining Professors / Societät der Bergbaukunde

Paper: Valgma, I. (2001) Map of oil shale mining history in Estonia

txt: Map of oil shale mining history in Estonia Ingo Valgma, M.Sc., PhD student The Mining Institute of Tallinn Technical University, Kopli 82, Tallinn, 10412, Estonia, Internet address http://www.ttu.ee/maeinst/ Phone: +372 620 38 50, Fax: + 372 620 36 96, E-mail: ingoval@cc.ttu.ee Poster will be presented as detailed map of oil shale mining technology, including illustrative diagrams and photographs, overview could be found on http://mgis.gz.ee/ Overview. Oil Shale is Estonia’s prime mineral resource. Oil shale is deposited in a single economic layer with thickness of 2,5 to 3 meters in depth of 7 to 100 meters in area of 2700 km2. Its production makes 70 percent of world’s oil shale production and two thirds of Estonia’s total mineral production. Mining activity started in 1916, peaked in 1980 and is ending in next 30 years. Therefore it is important to save oil shale mining history in easily accessible database. The Mining Institute of Tallinn Technical University has created geographically referenced database of oil shale. MapInfo Professional is used for mapping geology and mining situation. The map includes research and mining fields, mineral and overburden properties, underground and surface workings. Additionally technological diagrams and data are saved. For analyzing underground mining influences, exact current mining situation and previous situation is compared with surface topology in mined out areas. Open cast mining results are compared with aerial photos and digital base maps. Both underground and surface oil shale mining started by handwork. Analyses show that mining influence to the environment from this period has been minimum. As technology developed and political situation changed, the influence increased with raise of production capacity. The conditions for starting of oil shale mining and promoting of development were the war time fuel crisis, the lack of fuel mineral deposits, particularly of oil deposits environs, the interest for fuels by Russia and Germany, particularly for navy, good mining conditions and high quality of the oil shale, disengaged labor. The favorable reasons for liquidating mining activities in Estonia are elimination of interests of great powers, discovering of new oil and gas deposits elsewhere and the development of transportation of fuel minerals, deterioration of mining conditions, exhausting of best reserves and environmental reasons. Figure 1. General overview of the Baltic oil shale area The reason for oil shale exploitation in the area of former Russia was the crisis of fuel consumption in the time of World War I. At the beginning oil shale was used as a local fuel. It displaced coal in heating plants, locomotives, cement and lime furnaces. Oil shale mining began in Estonia province in 1916 for supplying Russian capital Petrograd (now St Petersburg). Figure 2. GIS is only way to save information of mining technology over large areas of flat laying deposits like Estonian Oil Shale deposit. Fragment of digital map of mining technology First period. Permanent kukersite mining started as soon as Estonia got its sovereignty in 1918. One of the oldest oil shale enterprises, State Oil Shale Industry, was established. The private companies formed almost at the same time and were owned by Estonian, as well as by German, English, Swedish and Danish owners. First fifteen years, all mines used strait works technology, which meant handwork. First stripping shovels and locomotives appeared in thirties. At the same time electric drilling began. Transition to the mechanized mining began in fifties. After that, longwall mining, which was widely used by Russian coal mining, was applied. For oil shale mining, double unit face method was used. Mines applied cutters, conveyors, electric locomotives and force ventilators. In all of the mines electrification was started. Second period. The technologies of oil shale retorting that were used elsewhere in the world, failed because of local oil shale properties and partly because of economic reasons. In Estonia reliable, inexpensive and productive technology for shale oil retorting was worked out at the beginning of thirties, during The First Estonian Republic. Since 1937 shale oil export value exceeded import value of other fuels. So Estonia achieved the independence in power what was the result of the government policy. The arrangements made by the government for oil shale industry were high depreciation rate, such as 20 per cent, relief inventory from import tax and great export subsidy. This launched the progress of shale oil industry in the Baltic Basin. Oil shale processing products became some of Estonia’s essential export items. Forty five per cent of it was exported in 1938. The oil shale products and shale oil accounted for eight per cent of Estonian export. Oil shale petrol was also produced, in 1938 only 6.4 per cent of that were exported that formed 1.6 per cent in 1939 of total Estonian export. The cement industry started using oil shale to improve the quality and economy of cement production. Thanks to oil shale, Estonia became independent of foreign fuel and energy. By 1940, eleven million tons of oil shale had been mined out and the annual production reached 1.7 million tons. After the World War II, the soviet authorities immediately started to develop shale oil processing, mostly for the Baltic Sea Navy and gas generation for the city of Leningrad. The central station electric power industry started to develop in Estonia in the 1950s. Several new mines were constructed and put into operation, in 1950, the annual oil shale output was three and half million tons, and by 1955 it reached seven million tons. The oil shale was used mainly as fuel at Tallinn, Kohtla Järve and Ahtme power stations, at Kohtla Järve and Kiviõli chemical plants and at Kunda Cement Plant. Third period. Building and putting into operation new power stations (Baltic Thermal Power Station in 1965, output 1400 MW, and Estonian Thermal Power Station in 1973, output 1600 MW) increased remarkably the demand for oil shale. To meet these needs, two new mines and three open casts were opened. At the same time four mines were abandoned. The increase of mining capacity was rapid, from 9.2 million tons in 1960 to 17.5 million tons in 1970. Oil shale mining production reached its maximum level of 31.35 million tons in 1980. Building of the third thermal power station was planned as well and due to this the annual output of oil shale mining was planned to be 50 million tons. Forth period. In 1981, Nuclear Power Station was built in Leningrad province, which caused the decrease in electricity demand in the northwestern part of the former USSR. This led to the decrease of oil shale production in Estonia, 29.7 million tons in 1980, 25.7 million tons in 1985, 21.2 million tons in 1990 and 12.1million tons in 1995. Prof. Reinsalu published the first scientific prognoses of the inescapable decrease in oil shale mining in 1988. According to this, the Estonian oil shale industry would vanish in the third decade of the next century. Since the beginning of the 1990s, the consumption and export of electricity had dropped in Estonia, as it has been in all East European countries. Oil shale output decreased slowly and is now at a level of 10 to 12 million tons in a year. Figure 3. MGIS (GIS for Mining) allows extracting information from maps of mining technology. Mining durations in underground sections. Map. MapInfo Professional has been used for analyzing digital maps of oil shale mining area. All maps are created in Mining Department of Tallinn Technical University. Additional information could be found on Internet location http://mgis.gz.ee/. GIS for mining (MGIS) has been used for extracting information, like following graph that is showing inescapable end of world largest operating oil shale deposit. Figure 4. World largest operating oil shale deposit is going to be abandoned Following technologies are described on the map: 1. Advancing and retreating mining, depth in meters H = 8 - 30 m, mining duration in years = from 1916 to 1967 2. Open cast mining by handwork, Depth in meters H = 0 - 6 m, Duration in years =, from 1918 to 1941 3. Open cast mining, with first stripping equipment, Depth in meters H = 6 - 10 m, Duration in years =, from 1928 to 1944 4. Longwall mining with, partial backfilling, Depth in meters, H = 9 - 40 m, Mining duration in years = from 1952 to 1989 5. Room & Pillar mining with scraper conveyor, Depth in meters H = 10 - 75 m, Duration in years = from 1960 to 2005 6. Room & Pillar mining with LHD, Depth in meters H = 40 - 80 m, Duration in years = from 1970 to 2030 7. Longwall mining, Depth in meters H = 10 - 40 m, Mining duration in years =, from 1971 to 2000 Current open cast mining, Depth in meters H = 3 - 27 m, mining duration in years = from 1919 to 2030 The study was supported by EstSF GRANT G3403

Paper: Map of oil shale mining history in Estonia I

Valgma, I. (2000). Map of oil shale mining history in Estonia I. In: Proceedings I. 5th Mining History Congress, Greece, Milos Conference Centre- George Eliopoulos, 2000: 5th Mining History Congress, Greece, Milos Conference Centre- George Eliopoulos, 2000. Agricola, 2000, 116 - 119. txt: Map of oil shale mining history in Estonia Oil Shale is Estonia’s prime mineral resource. Oil shale is deposited in a single economic layer with thickness of 2,5 to 3 meters in depth of 7 to 100 meters in area of 2700 km2. Its production makes 70 percent of world’s oil shale production and two thirds of Estonia’s total mineral production. Mining activity started in 1916, peaked in 1980 and is ending in next 30 years. Therefore it is important to save oil shale mining history in easily accessible database. The Mining Institute of Tallinn Technical University has created geographically referenced database of oil shale. MapInfo Professional is used for mapping geology and mining situation. The map includes research and mining fields, mineral and overburden properties, underground and surface workings. Additionally technological diagrams and data are saved. For analysing underground mining influences, exact current mining situation and previous situation is compared with surface topology in mined out areas. Open cast mining results are compared with aerial photos and digital base maps. Both underground and surface oil shale mining started by handwork. Analyses show that mining influence to the environment from this period has been minimum. As technology developed and political situation changed, the influence increased with raise of production capacity. The conditions for starting of oil shale mining and promoting of development were the war time fuel crisis, the lack of fuel mineral deposits, particularly of oil deposits environs, the interest for fuels by Russia and Germany, particularly for navy, good mining conditions and high quality of the oil shale, disengaged labour. The favourable reasons for liquidating mining activities in Estonia are elimination of interests of great powers, discovering of new oil and gas deposits elsewhere and the development of transportation of fuel minerals, deterioration of mining conditions, exhausting of best reserves and environmental reasons. General overview of the Baltic oil shale area The reason for oil shale exploitation in the area of former Russia was the crisis of fuel consumption in the time of World War I. At the beginning oil shale was used as a local fuel. It displaced coal in heating plants, locomotives, cement and lime furnaces. Oil shale mining began in Estonia province in 1916 for supplying Russian capital Petrograd (now St Petersburg). First period. Permanent kukersite mining started as soon as Estonia got its sovereignty in 1918. One of the oldest oil shale enterprises, State Oil Shale Industry, was established. The private companies formed almost at the same time and were owned by Estonian, as well as by German, English, Swedish and Danish owners. First fifteen years, all mines used strait works technology, which meant handwork. First stripping shovels and locomotives appeared in thirties. At the same time electric drilling began. Transition to the mechanized mining began in fifties. After that, longwall mining, which was widely used by Russian coal mining, was applied. For oil shale mining, double unit face method was used. Mines applied cutters, conveyors, electric locomotives and force ventilators. In all of the mines electrification was started. Second period. The technologies of oil shale retorting that were used elsewhere in the world, failed because of local oil shale properties and partly because of economic reasons. In Estonia reliable, inexpensive and productive technology for shale oil retorting was worked out at the beginning of thirties, during The First Estonian Republic. Since 1937 shale oil export value exceeded import value of other fuels. So Estonia achieved the independence in power what was the result of the government policy. The arrangements made by the government for oil shale industry were high depreciation rate, such as 20 per cent, relief inventory from import tax and great export subsidy. This launched the progress of shale oil industry in the Baltic Basin. Oil shale processing products became some of Estonia’s essential export items. Forty five per cent of it was exported in 1938. The oil shale products and shale oil accounted for eight per cent of Estonian export. Oil shale petrol was also produced, in 1938 only 6.4 per cent of that were exported that formed 1.6 per cent in 1939 of total Estonian export. The cement industry started using oil shale to improve the quality and economy of cement production. Thanks to oil shale, Estonia became independent of foreign fuel and energy. By 1940, eleven million tons of oil shale had been mined out and the annual production reached 1.7 million tons. After the World War II, the soviet authorities immediately started to develop shale oil processing, mostly for the Baltic Sea Navy and gas generation for the city of Leningrad. The central station electric power industry started to develop in Estonia in the 1950s. Several new mines were constructed and put into operation, in 1950, the annual oil shale output was three and half million tons, and by 1955 it reached seven million tons. The oil shale was used mainly as fuel at Tallinn, Kohtla Järve and Ahtme power stations, at Kohtla Järve and Kiviõli chemical plants and at Kunda Cement Plant. Third period. Building and putting into operation new power stations (Baltic Thermal Power Station in 1965, output 1400 MW, and Estonian Thermal Power Station in 1973, output 1600 MW) increased remarkably the demand for oil shale. To meet these needs, two new mines and three open casts were opened. At the same time four mines were abandoned. The increase of mining capacity was rapid, from 9.2 million tons in 1960 to 17.5 million tons in 1970. Oil shale mining production reached its maximum level of 31.35 million tons in 1980. Building of the third thermal power station was planned as well and due to this the annual output of oil shale mining was planned to be 50 million tons. Forth period. In 1981, Nuclear Power Station was built in Leningrad province, which caused the decrease in electricity demand in the north-western part of the former USSR. This led to the decrease of oil shale production in Estonia, 29.7 million tons in 1980, 25.7 million tons in 1985, 21.2 million tons in 1990 and 12.1million tons in 1995. Prof. Reinsalu published the first scientific prognoses of the inescapable decrease in oil shale mining in 1988. According to this, the Estonian oil shale industry would vanish in the third decade of the next century. Since the beginning of the 1990s, the consumption and export of electricity had dropped in Estonia, as it has been in all East European countries. Oil shale output decreased slowly and is now at a level of 10 to 12 million tons in a year. Ingo Valgma

Paper: Oil shale mining in Estonia and Russia

txt: UNESCO – EOLSS SAMPLE CHAPTERS COAL, OIL SHALE, NATURAL BITUMEN, HEAVY OIL AND PEAT – Vol. II - Mining of Oil Shale - Ingo Valgma and Jialin L. Qian ©Encyclopedia of Life Support Systems (EOLSS) MINING OF OIL SHALE Ingo Valgma Department of Mining, Tallinn Technical University, Estonia Jialin L. Qian School of Chemical Engineering, University of Petroleum, China Keywords : Aboveground mining ,Arm loader, Baltic oil shale, Blasting, Braking, Double handling, Double unit face method, Dragline, Drifting, Drilling, Fushun Open Pit Mine, Green River oil shale, Kukersite, Longwall mining, Magnetic suspension, Maoming mining area, Mineable reserves, Open cast mining, Open pit mining, Pillar, Ripper , Room and pillar mining , Selective winning, Shortwall stoping by handwork, Shovel, Strip mining , Stripping, Stripping ratio, Surface mining , Underground mining, Volga oil shale Contents 1. Introduction 2. Oil Shale Mining in Estonia and Russia 2.1 Mining Location 2.2 Mineable Reserves 2.3 History of Oil Shale Mining in Estonia and Russia 2.4 Development of Mining Technology in Estonia and Russia 2.5 Surface Mining in Estonia 2.6. Underground Mining in Estonia and Russia 2.7. Separation of Oil Shale from Waste 2.8. Economics and Organization 2.9. Future Trends of Oil Shale Mining in Estonia 3. Oil Shale Mining in China 3.1 Oil Shale Open Pit Mining in Fushun 3.2 Oil Shale Open Pit Mining in Maoming 3.3 Oil Shale Underground Mining in Huadian 3.4 Oil Shale Underground Mining in Huangxian 4. Oil Shale Mining in the USA 5. Oil Shale Mining in Brazil 6. Conclusions Acknowledgments Glossary Bibliography Biographical Sketches Summary In Estonia, oil shale has had a long history of commercial production since 1018. Until the end of the1990s, oil shale mines annually produced about 12 to 13 million tons. Almost half of the oil shale is exploited in surface mines with open cast technology; the other part is produced from underground mining. UNESCO – EOLSS SAMPLE CHAPTERS COAL, OIL SHALE, NATURAL BITUMEN, HEAVY OIL AND PEAT – Vol. II - Mining of Oil Shale - Ingo Valgma and Jialin L. Qian ©Encyclopedia of Life Support Systems (EOLSS) About 85% of oil shale mined is used for burning in oil shale power stations; 12% for retorting for obtaining shale oil; about 3% for cement factories. In Russia, the production of oil shale in the Leningrad mining area has dropped to about 2 million tons annually in recent years. It is mined underground. In China, the Fushun open pit mine has been operated for more than 70 years, mainly for coal production and also for oil shale, as a byproduct, which lies on the upper layer of the coal bed. Part of the oil shale mined is used for retorting for producing shale oil. Maoming oil shale mine started operation in the 1960s, and stopped in the 1990s due to the shutting down of the Maoming retorting plant. In Brazil, open pit mining has been carried out for producing oil shale, about several thousand tons daily, for Petrosix retorting. In USA, oil shale was exploited, but only used for pilot plant or prototype retorting tests. 1. Introduction Usually oil shale is at first mined out, and then it is pyrolyzed in retorts or burnt in boilers. Oil shale may also be retorted or gasified in-situ underground, thus obviating the mining process; however, underground retorting or gasification was only tested on a prototype scale in the USA, and in the former USSR in the past but this technology has not continued in commercial production. Just like coal, oil shale can be mined underground in the case of deep buried reserves; and oil shale can be mined aboveground, too. Oil shale deposits have now been exploited in Estonia, Russia, China, USA, Brazil, Israel, Germany, etc. 2. Oil Shale Mining in Estonia and Russia 2.1 Mining Location In the area of the former Russian Empire and USSR there are two regions where oil shale has been exploited. The first, the Baltic oil shale area, located at the Republic of Estonia and the Leningrad Province of Russia, near the Gulf of Finland, covers about fifty thousand square kilometers, which is the largest and the best known. The main oil shale, from the Middle Ordovician age, is named kukersite oil shale. The Baltic area includes the Estonian and Leningrad deposits and Tara occurrences, of which the first two are commercially exploited. The Estonian deposit is one of the largest commercially exploited oil shale deposits in the world with its total resources exceeding five billion tons of oil shale. The Leningrad deposit includes a small kukersite occurrence in Weimarn near St. Petersburg. UNESCO – EOLSS SAMPLE CHAPTERS COAL, OIL SHALE, NATURAL BITUMEN, HEAVY OIL AND PEAT – Vol. II - Mining of Oil Shale - Ingo Valgma and Jialin L. Qian ©Encyclopedia of Life Support Systems (EOLSS) The second known region is the Volga oil shale area, which exploits deposits located in Saratov province. The organic matter content of kukersite oil shale in Estonia ranges from 23% to 52%, making it one of the highest-grade oil shales in the world. Kukersite is carbonaceous and has a high organic content and low sulfur content. 2.2 Mineable Reserves In 1946, after previous investigations, the estimated oil shale resources in Estonia were one billion tons and in 1960 were 3.3 billion tons. The increase can be explained by the larger area for which the resources were calculated. Until 1998, the size of the Estonia oil shale reserves was determined on the basis of three characteristics: thickness, average calorific value, and depth of the mineable bed. The regulation concerning the geological exploration of the mineral, resources and the establishment of mineral reserves provided that oil shale could be regarded as a mineral resource if the calorific value of the bed is equal to or more than 6.1 Mj kg–1. The bed thickness should not be less than 0.5 m at the overburden thickness of up to 10 m or bed thickness is not less than 1.4 m at the overburden thickness of over 10 m. Estonia and Leningrad oil shale constituted basic mineral fuel resources for the USSR northwestern region, which required massive reserves. Thus a low criteria were established for the determination of oil shale reserves. The Soviet criteria proved unsuitable under new economic conditions. Furthermore, the characteristics applied in the eastern and central Baltic resource proved inadequate in the western area. The best criterion determining Estonia’s resources of kukersite oil shale is the energy rating of the bed in GJ m–2, implying the sum of the products of thickness, calorific values and densities of oil shale layers and limestone interlayers in all A-F beds. Estonian mining fields have an energy rating from 36.5 to 46.3 GJ m–2, with an average of 42.2 GJ m-2. The resources of the Estonian deposit consist of mineable or active reserves and additional or passive resources. The active reserve is defined as oil shale layer with energy rating equal to or exceeding 35 GJ m–2. If energy rating of a bed is below 35 GJ m–2 (about 10 MWh m–2), at the time suitable for surface mining, then auxiliary criteria are used. Auxiliary criteria include the total thickness, without limestone interlayers, of selectively mineable oil shale layers. A reserve block is formed to register the active reserves, within which the average calorific value of mineable oil shale layers exceeds 11 MJ m–2, and their summary thickness is over 10% of the burden thickness. The average energy rating of the bed in the oil shale exploration block registered as passive resources should be at least 25 GJ m–2. The reserves of the operating mines and open casts of Estonian oil shale deposits approximate 0.6 billion tons plus the reserves of exploration fields. According to the criteria, the active reserves of exploration fields exceed 2 billion tons of oil shale rock with limestone interlayers over 17 EJ of energy UNESCO – EOLSS SAMPLE CHAPTERS COAL, OIL SHALE, NATURAL BITUMEN, HEAVY OIL AND PEAT – Vol. II - Mining of Oil Shale - Ingo Valgma and Jialin L. Qian ©Encyclopedia of Life Support Systems (EOLSS) and passive resources amount for over 4 billion tons of oil shale rock or over 30 EJ of energy. Based on energy point of view, Estonian oil shale minefields have approximately one billion tons of proved reserves and the exploration fields have double these reserves. The Estonian oil shale resources are twice as large as the oil shale that has been mined out to the present time. The resources of oil shale rock in all exploration fields form 6.3 billion tons, and the energy resources amount to 48.6 EJ. Russian oil shale resources at the Leningrad deposit that occurs by the Narva River have an energy rating below 35 GJ m–2. The conclusion for data of Russian Leningrad and Estonian Baltic active oil shale deposits are 1 billion and 3.94 billion tons respectively. The second oil shale in the Baltic oil shale basin is Dictyonema shale from Cambrian age; analogous mineral in Sweden and Norway is named Alum shale. The peculiarity of the shale is the low content of organic matter and high content of sulfur, along with the metal content: Vanadium 1100 g t-1, Molybdenum 350 g t-1, and Uranium 300 g t-1. In Estonia and in Sweden, these particular shales have been raw materials for uranium production. - - - TO ACCESS ALL THE 16 PAGES OF THIS CHAPTER, Visit: http://www.eolss.net/Eolss-sampleAllChapter.aspx Bibliography Allred V., ed. (1982). Oil Shale Processing Technology, 230 pp. East Brunswick, New Jersey: The Center for Professional Advancement. [Presents mining information about the USA, Brazil, etc.] Baltic 21, An Agenda 21 for the Baltic Sea Region, Baltic 21 Series No 1/98 (1998). Adopted at the 7th Ministerial Session of the Council of the Baltic Sea States, Nyborg. [This is the official development plan for the Baltic region.] Hou X. L. (1986). Shale Oil Industry in China, 257 pp. Beijing: Hydrocarbon Processing Press. [Information on oil shale mining and other topics in China.] Kaukas A. and Teedumae A., eds. (1997). Geology and Mineral Resources of Estonia, Institute of Geology, Estonian Academy Publishers. [This book provides the latest information about Estonian resources.] Reinsalu E., ed. (1998). Oil Shale 15(2), Department of Mining, Tallinn Technical University, Tallinn. [This special issue of the journal presents new information about oil shale exploratory mining in Estonia.] Biographical Sketches Ingo Valgma is a lecturer in mining at the Mining Department of Tallinn University in Estonia. Jialin Qian is Professor at the School of Chemical Engineering, University of Petroleum, Beijing, China.

Paper: POST-STRIPPING PROCESSES AND THE LANDSCAPE OF MINED AREAS IN ESTONIAN OIL SHALE OPEN CASTS

1.1 POST-STRIPPING PROCESSES AND THE LANDSCAPE OF MINED AREAS IN ESTONIAN OIL SHALE OPEN CASTS [SLIDES] I. VALGMA The present study describes creating a digital map of oil shale surface mining technology and evaluating mining influences on the landscape. The data from the digital map of the Sirgala open cast show a constant increase in the overburden thickness. Overburden material thickness influences directly the future landscape but it also sets limits to stripping equipment parameters and productivity. The present open cast landscape was divided into four classes: afforested area, area with poor vegetation, graded area, and spoils. The second purpose of the study is saving information in an easily accessible form for the future. For this purpose geographic information system for mining is used. Introduction The minerals of Estonia are excavated in the amount of 10.5 million m3 per year. Yearly 7.4 million m3 of oil shale is mined, and half of this is mined in the open cast mines. The total surface mining amount in Estonia is 6.7 million m3 per year, and 54 % of it stands for oil shale mining. From this data a general rule follows: 1/3 of the volume of mined minerals comes from oil shale underground mining, 1/3 from oil shale surface mining, and 1/3 from surface mining of other minerals. Mining areas could be divided into five reclamation categories. First - mud excavation area - where mining takes place under water, is no subject for reclamation. Second - clay mining pits - are reclaimed to water storages, ponds or landfills. Third - sand and gravel quarries - are graded or formed as ponds. Fourth - limestone and dolostone quarries - form relatively deep ponds or are filled with waste. Among small-scale mining their reclamation is the most problematical one. Fifth - oil shale, phosphate rock and peat mining areas - are large due to thin horizontal bedding and require special reclamation. The largest Estonian surface mines are described as an example of large-scale mining operations and post-stripping processes. These open cast mines are largest by both area and production capacity and so cause also the largest influence to the environment and landscape. These three are the Aidu, Sirgala and Narva oil shale open casts, situating in the deposit wings where overburden thickness is smallest (Fig. 1). On the whole 120 km2 of overburden have been stripped in these mines. Fig. 1. Estonian oil shale deposit Calculations and charts in the present paper describe mostly the Sirgala open cast as the largest open cast mine in Estonia. Detailed description of the past processes in the mined-out areas let us understand, predict and save the information about several technological and environmental influences. Many of processes explain the reasons of forming the present landscape in these areas. The data about the equipment can help planning next trenches working in similar conditions. The data about steps of technological development of surface mining help us to retain historical data about large mineral extraction areas. A geographically referenced database represents a most suitable tool to study all these problems. Methods Geographic information system (GIS) for mining is used for describing and analysing spatial mining-related data. GIS is used for describing, in addition to technological problems, also post-technological processes. The main result is a digital map illustrating the oil shale mining technology. The present study presents the second stage of the map creation at the Mining Institute of Tallinn Technical University. During the first stage underground mining technology was mapped, the second stage includes the map of surface oil shale mining [1, 2]. Information on the map was taken from the technological maps of oil shale open casts, geological investigations, and aerial photographs and from the digital Estonian base map. Fig. 2. Mining sections in the Sirgala open cast The study included the following steps: collecting maps and references about the area, scanning, digitising and vectorising map data. The contours of the blocks mined in every mine section during a year were extracted and mapped. The database includes, in addition, the year of mining, height of the ground above the sea level and overburden thickness. As the result a digital surface mining map was created. The map (Fig. 2) includes stripping data and also aerial photographs and represents a basis for studying stripping dynamics, areas, volumes and landscape situation. Discussion Mapping calculations show that the total area of the mined sections in the Sirgala open cast is 6,532 ha. Aerial photographs from the year 1996 cover all the area except section No. 4[*]. Therefore in examples section No. 4 is excluded. The total production capacity of all Estonian oil shale open casts is 3 million m3 or 5 million tonnes of oil shale per year. Every mine produces, on average, 1 million m3 of oil shale per year. Oil shale yield is 3.4 tonnes per m2 of mined area; therefore, the total area of surface mining movement is 1.5 million m2 per year. As could be seen from the chart of the mined areas in the Sirgala open cast throughout its history (Fig. 3), its total annual movement area is 1 million m2. In the case of average rates the area should be around 0.5 million m2. In reality Sirgala’s load is 44 per cent of all open casts. This situation reflects either an overestimated yield of oil shale or oil shale overproduction. Figure 3 Stripping areas of Sirgala open cast from 1949 to 1999, thousands m2 per year Taking 80 m per year for an average shift of the mine face, the total length of operating sections is 20 km. On average, every open cast has a 6.5-km mining front, four mining sections with the length of 1.6 km and four haulage trenches. The width of the mining and haulage trenches varies from 25 to 55 m. The total height of the spoil forms after stripping and reclamation. Mined out oil shale bed with a thickness from 2.5 to 3 m also decreases the final height of the spoil by its thickness. Blasted overburden that consists of lime- and dolostone with clay requires 1.4 times more space than in the bank. The average loosening coefficient of quaternary sediments such as sand, peat, clay and moraine is 1.2. It means that the final height of the spoil surface in the Aidu open cast (see Fig. 1), where the total overburden thickness is 17 and the soft part of it 3 m, will be 4 m higher than the ground surface. In the Sirgala open cast the raise will be 4 m and in the Narva open cast 6 m. The height of the spoils of the overburden material is 3 m higher beside haulage trenches because of the additional material from the trench. The relative change in the surface height in other Estonian surface oil shale mines does not exceed 1 m. These mines are Kohtla, Kohtla-Vanaküla and northern section No. 4 of the Narva open cast. Possible surface mines like Tammiku-Kose, Sonda, Ubja and partly Aidu section No. 2 have the same parameters. For example, in the Kohtla open cast, in the beginning where the overburden thickness is less the spoil height is one metre lower, and after ten years the stripped spoil will be 1 m higher than the original ground. The data from the digital map of the Sirgala open cast show a constant increase in the overburden thickness. Weighted average of thickness of all sections show a constant increase from 6 m in 1950 to 9 m in 1962. Since 1963 till 1978 the thickness increased from 9 to 12 m varying from 6.5 to 16 m. Today the average thickness is 17 m, varying from 15 to 20 m. The overburden material thickness influences directly the future landscape but it also sets limits to stripping equipment parameters and productivity. Stripping capacities (Fig. 4) are therefore influenced by production demand, over-burden thickness and equipment capacities. The graph shows the amount and dynamics of casting overburden material in the Sirgala mine area. Figure 4 Stripping volumes in Sirgala open cast, thousands m2 per year From the beginning of mining, the area of a mine is influenced by haulage trenches. On average two trenches are excavated for every section. They follow the depth of the oil shale bed and are used for mineral haulage and process maintenance. Trenches will be open to the air for the rest of the lifetime of an open cast. They are the most changed elements of the landscape after mining. The area of open casts will be flooded. The depth and width of the trenches are greater than those of most of Estonian natural lakes or rivers. The surface area of the bottom of trenches is 1 ha per 400 m or 2.5 ha per 1 km. The average length of trenches in Estonian open casts is 5 km that makes their average area 12 ha. The relative depth of trenches varies from 8 to 38 m. Comparing to the lakes it equals the water depth in the Estonia’s deepest lake Rõuge Suurjärv. Question is, what the maximum water table height in trenches could be. The water table level depends on the level of water table in the Narva River that is 24 m above the sea level. The surface height of the mining area is 30 m above the sea level, and the minimum height of the bottom of oil shale bed equals the sea level. Due to this the depth of water in trenches will be up to 24 m. In the case of coagulation, the depth of water could reach 25 m or even more. The Sirgala open cast area has 18 such trenches. In practice, abandoned Maardu phosphate rock open cast is a good example of flooded trenches and reclaimed area. Although the overburden materials of these two mined minerals are different, the general view will be the same. The Maardu open cast abandoned in 1991 is surrounded by water channels with a width of 80 to 120 m and water depth of about 3 m. The angle of the trench walls is 35 to 40? like in the oil shale area. When trenches will be flooded in Sirgala and in other oil shale open casts, their water surface area will be 1.5 to 3 times greater than the present haulage road area. In surrounding and deeper trenches the width of the water table in channels could reach 150 m. However, the fact of their existing there causes another remarkable situation. Like in the Maardu mine area today, the channels will surround the reclaimed area and limit the accessibility of the area by transport facilities, which means less human impact on large afforested areas. From the point of view of environmental protection this will be one of favourable influences of surface mining on large and also remote areas. Another similarity with the Maardu mine concerns saving mining process data. Today only few maps and documents are available about the Maardu mine. Mapping its underground part is almost impossible due to the lack of map and other information, caused by changes in the enterprise ownership. The same situation could easily happen to oil shale industry. This brings out another aspects of the importance of the present study - saving information in an easily accessible form for the future. The present open cast landscapes could be divided into four classes (Fig. 5).The first one is the afforested (mainly with pines) area. The second one is the area with poor vegetation, small trees and bushes, fifty per cent of it being a rocky surface. Aerial photographs show it as a striped area. The third one is a graded area, mainly without vegetation but ready for planting. The fourth area has spoils that are not graded and have no vegetation, their surface angles reaching the angle of the repose, maximum 45?. In the presented aerial photograph one-year stripping equals to 1-3 trenches (Fig. 6). Figure 5 Reclamation dynamics of Sirgala open cast area Oil shale surface mining has influenced northeastern Estonian landscape since the first days of oil shale industry. From 1916 to 1927 handwork was used for stripping [3]. Due to this the material of spoils was fine enough for reclaiming, and today this area is afforested or urbanized. Depending on the technology, depth of oil shale bed and political circumstances [3-6], the landscape and surface material varies slightly (the Table). Which of these stages has been best for recovering the nature, is a question for ecologists. Fig. 6. Sharp spoils in the Sirgala open cast In surface mines the same range of equipment is used for stripping low-bedded deposits as for construction, amelioration and agriculture. The maximum reach of construction excavators is usually 6 m; the height of the blasted rock bench can be 1.5 of the excavator reach. This limits the oil shale mining area where such technology could be used to the bedding depth from 2 to 10 m. This 10-metres-limit was reached in the Viivikonna[*] open cast in 1967 and in the Sirgala in 1970. In the Narva mine the mining started in 1970 in the depth of 18 to 19 m, and in 1992 in the northern section - in the depth of 6 to 7 m. In the Aidu open cast, half of section No. 2 (stopped today) has the overburden thickness below 10 m, which could be compared to the present situation in the Narva open cast. Conclusion Oil shale surface mining forms 1/3 of 10.5 million m3 of minerals excavated yearly in Estonia. The Sirgala open cast produces 44 per cent of the surface-mined oil shale. Due to its large area, average mining conditions and remarkable production capacity Sirgala is the best example for illustrating the method of open cast mining, post-mining processes and landscape formed in the oil shale surface mining area. The present study describes creating a digital map of oil shale surface mining technology and evaluating mining influences on the landscape. The data from the digital map of the Sirgala open cast show a constant increase in the overburden thickness. Overburden material thickness influences directly the future landscape but it also sets limits to stripping equipment parameters and productivity. Stripping capacities are therefore influenced by production demand, overburden thickness and equipment capacities. Reclamation technology has reached a nature-friendly level and causes no harm, except trenches, to the landscape. Trenches are the most changed elements of the landscape after mining. Their depth and parameters are greater than those of most of Estonian natural lakes or rivers. Their depth of water could reach 24 m. Oil shale mines, due to shale thin horizontal bedding require special reclamation after their exhausting. The present open cast landscapes could be divided into four classes: afforested area; area with poor vegetation; graded area; spoils. Another aspect of the present study is saving information in an easily accessible form for the future. For this purpose GIS for mining is used. This study is a part of the development plan of Ida-Viru County and Estonian Oil Shale Company. Acknowledgements This study was supported by Estonian Science Foundation (Grant No. G3403) and by support 0141321s99 for postgraduate studies at Tallinn Technical University. REFERENCES 1. Valgma, I. Mapping potential ground subsidence areas of Estonian oil shale deposit // Proc. of Conference on Mining Law and Mining Safety. Tallinn, 1999 [in Estonian]. 2. Valgma, I.Mapping potential areas of ground subsidence in Estonian underground oil shale mining district // Proc. of the 2nd International Conference - Environment. Technology. Resources. Rezekne, Latvia, 1999. 3. Fifty Years of Oil Shale Mining in Estonian SSR / Valgus. – Tallinn, 1968 [in Estonian]. 4. Sirgala 35 / Disantrek. - Tallinn, 1997 [in Estonian]. 5. Work of the Open Cast – Result of the Work of Team and Shift / Valgus. – Tallinn, 1986 [in Russian]. 6. Teetlok, K. Reclamation of Land Disturbed by Mining of Mineral Resources and Their Influence to the Environment of Estonia / Institute of Geography, UT, Tartu, 1995 [in Estonian]. Presented by E. Reinsalu Received March 3, 2000 Fig. 3. Stripping areas of theSirgala open cast from 1949 to 1999, thousands m2 per year Fig. 4. Stripping volumes in the Sirgala open cast, thousands m2 per year Fig. 5. Reclamation dynamics of the Sirgala open cast area [*] Aerial photographs of the eastern zone are missing because of the country border existing there. [*] Viivikonna open cast was joined to Sirgala in 1987. [SLIDES]