A mining extraction system with advancing longwall as a method of protecting technical objects and an element of rational deposit management

Underground mining leads to many adverse changes in the natural environment and also affects building structures and elements of urban technical infrastructure. Protective pillars are usually designed to protect these objects. As is well known, extraction within these pillars may only be conducted taking special actions to insure proper protection of existing infrastructure against mining damages. Mines usually refrain from the extraction of protective pillars, which results in the specific loss of reserves and interferes with the rational management of a deposit. At present, longwall extraction using the so-called “advancing longwall” appears to be one of few feasible methods. Thismethod can be used for the protection of linear objects like railways,motorways, pipelines, etc. This paper presents considerations concerning the use of an extraction system with an advancing longwall for terrain deformation minimization. For these purposes, a theoretical model was designed using the Wolfram Mathematica 9 calculation system. The W. Budryk-S. Knothe theory was employed to build the model for asymptotic and transient state of deformation. The solution contains a full space-time model, enabled for analyses of front shapes, its dimensions and the extraction velocity’s influence on tilt and horizontal strain values along the longitudinal axis of a linear object of technical infrastructure located at the surface. The rock mass properties were considered too, using selected values of time factor c which can be viewed as a parameter describing the rate of subsidence trough transition from the extracted seam toward the surface. The results presented in this paper may be helpful in designing the proper parameters of a central longwall when planning the extraction of protective pillars.