Abstract:In underground coal mining engineering, one of the most important tasks is to monitor, predict and manage the surface subsidence due to underground coal excavation. The impact of underground mining excavation reflects as subsidence of the overlying strata and the formation of surface depressions soon after excavation. The surface subsidence is one of many natural processes that exhibit a progression from small beginnings that accelerate and approach a climax over time. When detailed data is lacking, a logistic function is often used. In this paper, the analysis of the surface subsidence above underground mining sites in the Velenje Coal Mine by using a modified sigmoid function (surrogate of logistic function), with the common "S" shape, is introduced. Furthermore, the time estimation of the next and the final epoch measurement is considered.

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Coal plays a fundamental role in global development, but the coal mining industry exerts impact on the environment, society and economy. Kolubara Coal Company produces about 30 million tonnes of coal, and digs about 70 million m3 of overburden per year. The main result of surface coal is certainly taking agricultural land, so that surface mines, which affect large areas in Kolubara, about 100 hectars a year, causing a number of problems related to the recultivation of degraded area after coal extraction. The lignite extraction through the method of opencast mining in Kolubara is about 60 years old. The previous exploitation usage is characterised by the fact that the disposal of overburden is made non-selectively, whereas the surface solum is not being preserved. The recultivation is carried out in parallel with overburden excavation. It is necessary to preserve the fertile solum through selective excavation in order to bring the soil back to its previous purpose - agricultural production. The objective of this paper is mainly to point out the need for the further expansion of the utilization of fossil fuels, which in turn reduces the emission of CO2, and thus reduces or prevents global climate changes on Earth. In addition to that, bringing back deteriorated terrains to their previous purpose - agricultural production, or the afforestation - contributes to the maintenance of ecological balance in nature, which then makes coal mining sustainable.

After building underground constructions, spatial parameters monitoring is essential due to safety and statuary reasons. Therefore after completion of work in tunnels often supervision projects follow which include cross sections measurements, as well as ground and secondary wall layer deformations monitoring during consolidation era. Conventional approaches to achieve this type of documentations are different, however their downside is often that they are time consuming and even with combination of independent contractors, collected data is often deficient and corrupted with rough interpolations. Terrestrial 3D laser scanning (TLS) represents alternative approach to conventional monitoring methods [1]. With engineer planning approach, field work and data interpretation, TLS technology allows systematical and fast acquisition of shape and spatial orientation of complex objects and all their components. In case of shorter railway tunnels (up to 360 m) data for clearance analysis in correlation of standard cargo and tunnel surface, was captured with terrestrial 3D laser scanning method. Control of tunnel clearance is usually performed analogously and on conventional low equidistant cross section survey method. Considering that in this article we deal with relative old tunnels, in which there is no constant transversal profile but huge amount of geometric anomalies, simulation verification could be performed only with hi-grid definition survey method. With TLS larger amount of tunnels were measured and clearance analysis simulations for real case of standard cargo profile was made, based on radius and railway inclination of the tunnel. Standard or non-standard cargo transport planning with computer simulation now can be done in relatively short time. In this article is presented integration of TLS in case study of short railway tunnels with focus on clearance analysis applications with interactive and user friendly visualization for data interpretation. Other methods for different spatial parameters interpretations in underground constructions are presented as well.

Abstract:The Velenje coal mine (VCM) is situated on the largest Slovenian coal deposit and in one of the thickest layers of coal known in the world. The thickness of the coal layer causes problems for the efficiency of extraction, since the majority of mining operations is within the coal layer. The selected longwall coal mining method with specific geometry, increasing depth of excavations, changes in stress state and naturally given geomechanical properties of rocks induce seismic events. Induced seismic events can be caused by caving processes, blasting or bursts of coal or the surrounding rock. For 2.5D visualization, data of excavations, ash content and calorific value of coal samples, hanging wall and footwall occurrence, subsidence of the surface and coal burst source locations were collected. Data and interpolation methods available in software package Surfer ® 12 were statistically analyzed and a Kriging (KRG) interpolation method was chosen. As a result 2.5D visualizations of coal bursts source locations with geomechanical properties of coal samples taken at different depth in the coal seam in the VCM were made with data-visualization packages Surfer ® 12 and Voxler ® 3.

Izvleček UDK 622.02 Sebastjan Konič, Mihael Ribičič & Milivoj Vulić: Prispevek k preverjanju zdrsa skalnega bloka z modelom medsebojne preslikave oblakov točk Osnovni cilj članka je ugotoviti ali se je skalni blok, na katerem stoji grad Črni kal, nekoč stikal s steno Kraškega roba. Ugotovitev se podaja na osnovi izdelave primerjave oblike obeh morebitnih stičnih ploskev, ki sta predstavljeni z velikim številom v prostoru določenih točk. Ta oblak točk je bil zajet s 3D terestričnim laserskim skeniranjem. Na podlagi ugotavljanja geoloških in morfoloških značilnosti skalnega bloka Črni kal in stene Kraškega roba je bilo zbrano 12 karakterističnih parov korespodentnih (ustreznih) točk, v parih po ena iz vsake stene. Z uporabo metode a ne 12 parametrične preslikave so bili izračunani transformacijski parametri preslikave enega oblaka v drugega. Ker so za to preslikavo dovolj 4 pari točk, za boljše rezultate pa je bilo uporabljenih 12 parov točk, je bila zaradi večjega števila parov točk uporabljena metoda najmanjših kvadratov (MNK). S pomočjo tako dobljenega transformacijskega vektorja je bil referenčni oblak točk skalni blok Črni kal preslikan za velikost vektorskega premika nazaj v oblak transformiranih točk, ki naj bi se prekrival z referenčnim oblakom točk stene Kraškega roba. Primerjava referenčnega oblaka točk Kraški rob in oblaka preslikanih transformiranih točk je pokazala, da je skalni blok Črni kal kot blokovni plaz zdrsnil za 4,7 m v smeri S-SW. Statistična analiza prekrivajočih se oblakov točk je pokazala, da kar 95 % točk pade v razdaljo manjšo od 0,74 m, kar potrjuje postavljeno hipotezo, da je bil skalni blok na katerem stoji grad Črni kal nekoč del stene Kraškega roba, od katere se je najmanj pred 11. stoletjem odtrgal in se vzporedno premaknil kot blokovni plaz. Ključne besede: zdrs skalnega bloka, lociranje karakterističnih parov korespodentnih točkovnih entitet, a na 12 parametrična transformacija, rotacijsko-deformacijska matrika, translacijski vektor.

With the exploitation of underground sources, nature receives a huge negative impact on the local environment introducing surface subsidence. A mining region needs to be observed in sequences before, during, and after coal extraction from the coal mine. Different measuring methods exist to monitor subsidence, and all of them apply various instrumentation. A choice of methodology depends on access to a field of observation and requested accuracy. Obviously, the most accurate results provide geometric leveling, but, many times, the terrain does not allow surveyors to walk over the dangerous outfields. Looking for the most adequate and feasible method, this research did a comparison between observation of the same points, applying statistical analysis of differences between the reference points heights, and tested methods. Monitoring procedure comprised utilization of total stations (TS), global navigation satellite system (GNSS), and unmanned aerial vehicles (UAV). In this paper, the Velenje coal mine was taken as a case study, and observation data were collected during 2017.

Impacts of underground mining have been reduced by continuous environmental endeavors, scientific, and engineering research activities, whose main object is the behavior and control of the undermined rock mass and the subsequent surface subsidence. In the presented Velenje case of underground sublevel longwall mining where coal is being exploited both horizontal and vertical, backfilling processes and accompanying fracturing in the coal layer, and rock mass are causing uncontrolled subsidence of the surface above. 3D point clouds of the study were acquired in ten epochs and at excavation heights on the front were measured at the same epochs. By establishing a sectors layout in the observational area, smaller point clouds were obtained, to which planes were fitted and centroids of these planes then calculated. Centroid heights were analyzed with the FNSE model to estimate the time of consolidation and modified according to excavation parameters to determine total subsidence after a certain period. Proposed prognosis approaches for estimating consolidation of active subsidence and long term surface environmental protection measures have been proposed and presented. The C2C analysis of distances between acquired 3D point clouds was used for identification of surface subsidence, reclamation areas and sink holes, and for validation of feasibility and effectiveness of the proposed prognosis.