The study concentrates on analysis of heterogeneous rock mass deformations in the final years of underground coal extraction and during the revitalisation period after the end of mining. The research has been carried out in the Walbrzych Coal Basin where underground mining ceased at the end of the 20th Century. In the paper results of initial stages of ground deformation studies on a fragment of the Walbrzych mining grounds concerning analysis of benchmark height changes in a selected levelling line has been described. The results indicate ground subsidence in the period immediately after end of coal extraction and change to a steady uplift of the ground a few years later (2000-2008). Abnormal changes of heights in tectonic fault zones have also been observed. These could be related to heterogeneous rock mass reaction during the revitalisation period., Jan Blachowski, Stefan Cacoń and Wojciech Milczarek., and Obsahuje bibliografii
Secondary deformations are ground movements occurring in areas of ceased underground mining. These are associated with delayed readjustment of rock mass resulting in subsidence, discontinuous deformations (sinks, cracks, etc.) due to destruction of underground, usually shallow, workings, and elevation of ground surface in response of rock mass to rising groundwater levels following the end of mine water drainage. Comparative analysis of secondary deformations in two former mining areas in the first period after cessation of underground hard coal mining is the subject of this study. We used ERS-1/2 and Envisat satellite radar interferometry data processed with PSInSAR technique and GIS to map vertical (in satellite’s line of sight, LOS) movements of the surface and analyse them in relation to location of coal fields and underground water table rise. In the study, two areas have been compared, the Ostrava city in the Czech part of the Upper Silesian Basin and the Wałbrzych Coal Basin in Poland. The results of analyses based on the results of PSInSAR processing between 1995 and 2000 for the Wałbrzych site indicate uplift (up to +12 mm/year) in closed parts of coal fields and subsidence (up to -8 mm/year) in areas of declining mining. Results of PSInSAR analysis over the Ostrava site indicate decaying subsidence after mine closures in the rate of up to -6 mm/year during 1995-2000. Residual subsidence and gentle uplift have been partly identified at surroundings of closed mines in Ostrava from 2003-2010 Envisat data. In Wałbrzych gentle elevation has been determined from 2002 to 2009 in areas previously subsiding. and Blachowski Jan, Jiránková Eva, Lazecký Milan, Kadlečík Pavel, Milczarek Wojciech.
The Rana Gruber iron oxide mining company in Norway has started to develop a new underground production level in order to continue operation in the Kvannevann mine. The planned change of mining system to sub-level caving (SLC) involves the removal of protective pillars below the former Kvannevann open-pit. Surface deformation on the hanging-wall and footwall sides of the deposit and caving of rock into the old pit is expected. When uncontrolled, this represents a threat to the underground mining operation below the open-pit. Trial removal of the protective pillar in the western part of the deposit has already caused fracturing of the rock mass on the hanging-wall side. Therefore, with the aim to monitor and control the rock mass deformation process in this area and ensure safe operation of the mine, a monitoring system based on periodic total station and GPS measurements in a three-tier control-measurement network has been developed and tested. In this paper the concept of this system, results of field work and recommendations for the system implementation is presented. The proposed concept has been used to implement a real system in the mine., Jan Blachowski, Steinar Ellefmo and Erik Ludvigsen., and Obsahuje bibliografii
Combination of numerical models of deformations and repeated geodetic measurement results provide reliable information on the state of the rock mass in a mining area and support planning and control of the mining operation. The paper describes the concept of integrated monitoring and analysis of rock mass deformation in the Kvannevann iron ore mine (Norway) using sub-level caving (SLC) method. Geodetic control network developed for periodic measurements of surface subsidence and a source of geometrical data for numerical modelling of deformations using finite element method (FEM) has been characterised. Focus is given to the results of initial numeric al analyses with FEM of rock mass deformations due to SLC mining. The results of the modelling provided information on possible extent of deformation zones on the mining ground surface once mining with new method commences., Jan Blachowski and Steinar Ellefmo., and Obsahuje bibliografické odkazy
Underground mining hard coal in the area of Walbrzych ended in the late 90-ties of the last Century. Its effects on the state of heterogeneous rock mass (complicated geology and tectonics) is still evident and not known precisely. Analysis of levelling measurement results carried out after the end of mining activity (1997-2008) for part of the former “Thorez” mine indicates increased rock mass surface activity in tectonic zones. With the aim to continue monitoring of the rock mass surface movements on the area of former mining grounds a research satellite GPS network (7 points) has been established and supplemented with new precise levelling lines linked to the existing 2nd class levelling network. Location of these points takes into consideration, among other things geology and tectonics of the Walbrzych Basin and areas of underground mining activity. In this paper work on the design and construction of the research satellite GPS and levelling networks has been described and the first measurement campaign carried out in September 2009 has been presented. Its results will form foundation for complex studies of rock mass surface in the next measurement epochs., Jan Blachowski, Wojciech Milczarek and Stefan Cacoń., and Obsahuje bibliografii