In this research study I have presented the results of monitoring and measuring of the instability appearance on the large open-pit coalfield mines in Serbia like: KOLUBARA, KOSOVO, KOSTOLAC, as well as the possibility of caving time forecast and/or caving preventing.
Dans ce travail j'ai presente' des resultats d'observatians et des measures de lapparition d'instabilite' sur les grands mines de'couvertes du charbon an Serbia les mines KOLUBARA, KOSOVO, KOSTOLAC, avec la posibilite' de la prevision du temps de demobilition c'est dire la stabilite" des mines.
In disem Referat sind die ergebnisse der begleitung und Messung die Erscheinigungen Unstavbilitat auf groben Tagebauen der Serbiens dargestelit, mit msglichkeit prognasirung die zeit Rutsebung der Böschung so wie die Prewentive und zwar KOLUBARA, KOSOVO, KOSTOLAC.
In Serbia three large coalfields have been developed: the ones of KOLUBARA, KOSOVOMETOHIYA, and KOSTOLAC. KOLUBARA coalfield is situated in the central part of Serbia, 50 km. away, to the south, from the city of Beograd, near by the town of Lazarevac. The coalfield have been investigated by deep boreholes and underground mining as well as by the existing open pit mining. The coal belongs to the Tertiary respectively to Pliocene formation, and represents the younger lignites. In Kolubara coalfield the geological reserves of 3.8 billion tons of lignite have been found, and all of them can be exploited by open pit mining. In Kolubara coalfield three open-pit mines have been opened, and they are: ‘Polje B’, ‘Polje D’, and ‘Tamnava -Istok field’. The forurth one - ‘Tamnava-Zapad field’ is in the phase of opening. The open-pit mine ‘Polje D’ on which certain investigations have been made, gives the production of 15 million tons of lignite per year, and after the reconstruction, which is under way, it should reach capacity of 18.8 million tons of lignite per year. Excavation of overburden and coal is being done by the ECL (Excavator, belt Conveyor, Loader) and ECS (Excavator, belt Conveyor, Stacker) systems. The excavated coal is transported to the separation plant where it is crushed and separated. The fine fractions are used by termal power plants, and the coarse ones by the other consumers. During exploitation many problems appear, and if they are not solved in time, they can make damages, which may imperil workers and equipment. One of the problems, which is present on the large open-pit coalfields, like Kolubara, Kosovo and Kostolac, is the problem of stability of working floors. It is known in theory as well as in practice that instability on the working floors is preceded by the cracks which are necessary to be noticed in time. Observation of the initial cracks as the precedence of instability existed on the mentioned fields, but with delay. The necessity for timely observation of the deformations with the aim of prevetive actions, required installation of monitoring systems on the supposed endangered places. Monitoring of the deformations on athe potentially instable working floor is under way in KOLUBARA on the open-pit mine Tamnava-Istok, and it will be explained in detail in the following text.
The results of many year research of the instability appearance on the coalfields KOLUBARA, KOSOVO and KOSTOLAC, that is to say on their open-pit mines: Polje D, Tamnava-Istok, Belacevac, and Drmno, have been presented in this text. The research consisted of the field observation and measuring as well as of the laboratory testing of the respective samples obtained by drilling.The results of the monitoring of the former many year instability apperances (2,3,5) show that it is the type of progressive fracture with the caving machanism shown on Fig. 1.