Linear discontinuous deformations created on the surface as an effect of underground mining and local geological conditions-case study

Underground mining negatively impacts the rock mass and land surface, as well as the objects located on it. One of the forms of such impact are linear discontinuous deformations, which presently in Polish Upper Silesian Basin conditions are more and more often accompanied by underground mining. Discontinuous deformations of mining origin not always arise on the surface, resulting from the occurrence of unfavorable geological and mining factors, and create different forms, mainly ground steps, cracks, and fissures. Presented in this article results of the research concern the problem of the occurrence of linear discontinuous deformations in the area of the greatest Polish hard coal deposit, Upper Silesian Basin, where several unfavorable factors triggered the system of linear discontinuous deformations in the shape of ground steps. Ground steps caused several damages to building objects, small architecture elements, and roads in surrounding area. One of the most important objects exposed to damage threat here is an old historic church. Ground steps occurred as a joined effect of underground mining influences together with impact of fault zones located close to the church and probably activated by mining works. In the paper, mining and geological conditions have been discussed, that led to arising of discontinuous deformations on the surface. Apart from description of mentioned factors, detailed calculations were carried out aimed at recognition of probable distribution on the surface of subsidence, horizontal displacement, and horizontal strain around the church. Their contribution to ground steps creation process has been discussed as well.