Mining activity influence on the environment belongs to the most negative industrial influences. Land subsidence can be a consequence of many geotectonic processes as well as due to anthropogenic interference with rock massif in part or whole landscape. Mine subsidence on the surface can be a result of many deep underground mining activities. The presented study offers the theory to the specific case of the deformation vectors solution in a case of disruption of the data homogeneity of the geodetic network structure in the monitoring station during periodical measurements in mine subsidence. The theory of the specific solution of the deformation vector was developed for the mine subsidence at the Košice-Bankov abandoned magnesite mine near the city of Košice in east Slovakia. The outputs from the deformation survey were implemented into Geographic Information System (GIS) applications to a process of gradual reclamation of whole mining landscape around the magnesite mine. After completion of the mining operations and liquidation of the mine company it was necessary to determine the exact edges of the Košice-Bankov mine subsidence with the zones of residual ground motion in order to implement a comprehensive reclamation of the devastated mining landscape. Requirement of knowledge about stability of the former mine subsidence was necessary for starting the reclamation works. Outputs from the presented specific solutions of the deformation vectors confirmed the multi-year stability of the mine subsidence in the area of interest. Some numerical and graphical results from the deformation vectors survey in the Košice-Bankov abandoned magnesite mine are presented. The obtained results were transformed into GIS for the needs of the self-government of the city of Košice to the implementation of the reclamation works in the Košice-Bankov mining area.
An analysis of the impact of mining with caving on the surface shows that a type of rock mass strata seems to be one of the critical factors affecting the process. Correlating the values of mining-induced surface deformation with the rock mass structure and the state of its disturbance is of crucial importance. Therefore, if other mining conditions are left unaffected, then those factors exert the key influence on a course and distribution of subsidence and rock mass deformation. A proper description of rock mass type and properties also seems rational for a proper determination of prediction parameters, especially in the case of a multi-seam coal mining, and/or the exploitation carried out at considerable depths. A general outcome of the study discussed in this paper is the development of the methodology and model practices for determining the rock mass type and, as a result, for selecting the optimal values of parameters for predicting the values of surface subsidence in relation to particular geological and mining conditions. The study proves that the type of rock mass may be described by such factors as the influence of overburden strata, the influence of Carboniferous layers, the disturbance of rock mass and the depth of exploitation.
The geodetic measurements optimization problem has played a crucial role in the mining areas affected by continuous ground movement. Such movements are most frequently measured with the classical geodetic methods such as levelling, tachymetry or GNSS (Global Navigation Satellite System). The measuring techniques are selected with respect to the dynamics of the studied phenomena, surface hazard degree, as well as the financial potential of the mining company. Land surface changes caused by underground exploitation are observed with some delay because of the mining and geological conditions of the deposit surroundings. This delay may be considerable in the case of salt deposits extraction due to slow convergence process, which implies ground subsidence maximum up to a few centimeters per year. Measuring of such displacements requires high precision instruments and methods. In the case of intensely developed urban areas, a high density benchmark network has to be provided. Therefore, the best solution supporting the monitoring of vertical ground displacements in the areas located above the salt deposits seems to be the Sentinel 1-A radar imaging satellite system. The main goal of the investigation was to verify if imaging radar from the Sentinel 1 mission could be applied to monitor of slow ground vertical movement above word heritage Wieliczka salt mine. The outcome of the analysis, which was based on DInSAR (Differential SAR Interferometry). technology, is the surface distribution of annual subsidence in the period of 2015-2016. The comparison of the results with levelling confirmed the high accuracy of satellite observations. What is significant, the studies allowed to identify areas with the greatest dynamics of vertical ground movements, also in the regions where classical surveying was not conducted. The investigation proved that with the use of Sentinel-1 images sub centimeters slow vertical movements could be obtained.
Geodesic measurements of mining area deformations indicate that their description fails to be regular, as opposed to what the predictions based on the relationships of the geometric-integral theory suggest. The Knothe theory, most commonly applied in that case, considers such parameters as the exploitation coefficient a and the angle of the main influences range tgβ, describing the geomechanical properties of the medium, as well as the mining conditions. The study shows that the values of the parameters a = 0.8 and tgβ = 2.0, most commonly adopted for the prediction of surface deformation, are not entirely adequate in describing each and every mining situation in the analysed rock mass. Therefore, the paper aims to propose methodology for determining the value of exploitation coefficient a, which allows to predict the values of surface subsidence caused by underground coal mining with roof caving, depending on geological and mining conditions. The characteristics of the analysed areas show that the following factors affect surface subsidence: thickness of overburden, type of overburden strata, type of Carboniferous strata, rock mass disturbance and depth of exploitation. These factors may allow to determine the exploitation coefficient a, used in the Knothe theory for surface deformation prediction.