Abstract
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.
Highlights
Environmental protection is becoming an integrated part of mining policies and technologies.Protecting the surface, its natural, economic, and other values from the effects of mining is an important part of ecological endeavors [1,2]
In order to predict surface subsidence that occur under the influence of underground excavation by vertical extraction, we considered the real excavation height in each centroid above the excavation
It can be observed that, considering the real excavation height, the bottom of the surface subsidence trough cannot be flat if the excavation height is not constant
Summary
Environmental protection is becoming an integrated part of mining policies and technologies.Protecting the surface, its natural, economic, and other values from the effects of mining is an important part of ecological endeavors [1,2]. In addition to general degradation, mining production is increasingly moving to urban areas, where much more important infrastructure is at risk [3,4]. The mining organization is obliged to implement direct protective measures on the surface or underground infrastructure and water regime within the exploitation area [5]. The measured displacements and deformation of the surface are legal proof of the incurred mining damage. Obtaining and analyzing these data is the starting point for evaluating the prognostic theories and their rational application. A change in shape in the vertical direction (subsidence) is observed between the initial and final state of the surface when equilibrium in the undermined rock mass is reached. The undermining process takes place in space and time, from
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