Abstract
Land subsidence in the area of the city of Walbrzych (SW Poland) has been a consequence of underground mining of hard coal. Exploitation of multiseam deposit took place for several 100 years and ended in the late 90’ties of the twentieth century. During this time, many buildings and constructions were affected by subsidence-related damages and new landforms including mining waste dumps have developed on the surface in a consequence of underground extraction of coal. Previous studies indicated that cumulative subsidence calculated with the empirical Knothe theory reached −22 m, whereas calculations based on results of cartographic data processing showed more than −30 m (± 3 m) pointing to insufficient reliability of traditional methods when applied in complex and complicated conditions (multiseam and steeply inclined deposits). Present-day height of manmade landforms in areas affected by subsidence reaches 63 m (± 3 m). Therefore, in the presented research, a weighted spatial regression method has been proposed for analysis and modelling of mining induced land subsidence. The study concerned the former Walbrzych coal mine area and the 1886–2009 period. The subsidence modelling has been done in geographic information systems with geographically weighted regression (GWR) method that allows for spatial variability of subsidence factors. Four, out of the analysed seven, subsidence factors were identified as significant (thickness, inclination and depth of coal levels and surface slope) and used as independent (explanatory) variables in construction of the subsidence model with the GWR method. The validated model was used to estimate subsidence in up to now unmapped areas transformed by manmade landforms. The maximum predicted subsidence in these parts for the 1886–2009 period reaches −10.5 m. In the result, a spatial representation (hybrid map) of subsidence for the entire Walbrzych coal mine has been produced.
Highlights
Subsidence is a time-dependent deformation of the ground’s surface caused by readjustment of the overburden above voids created by underground extraction of minerals
Recent publications on mining subsidence can be generally categorised into two groups, the first includes investigations concentrating on monitoring and observation of subsidence, and the second focuses on research into modelling and predicting subsidence and the related hazards to the surface and infrastructure
The results of this study indicate that the presented method of modelling mining subsidence with weighted spatial regression model is reliable and can be used as an augmentation and alternative to traditional subsidence modelling methods including prediction and assessment of this process in areas with limited amount of surveying data and in cases of complicated mining conditions
Summary
Subsidence is a time-dependent deformation of the ground’s surface caused by readjustment of the overburden above voids created by underground extraction of minerals. Current studies focusing on monitoring subsidence on mining grounds with geodetic (precise levelling, GPS) and modern remote sensing techniques include work by Raucoules et al (2003) who have described application of differential InSAR (DInSAR) technique to detect and monitor ground deformation on a test site of underground exploitation of salt using solution mining method in France. They have shown that the geometry of the subsidence bowl is different and larger than the one assumed from groundbased geodetic measurements. They have proved that results from InSAR are consistent with the ground levelling measurements and have used it for mapping long-term subsidence in that area
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