The Legnica deposit is one of the most prospective in the context of future lignite mining. Its extraction will be inseparable from the removal of the rocks of the overburden, the volume of which is very large. Due to the raw material properties, some of the rocks can be classified as accompanying minerals. The raw material identification of overburden sediments in the Legnica lignite deposit is insufficient. So far, they haven’t been the subject of detailed and comprehensive research to prove their usefulness. The article was a summary of the knowledge on this subject. The following should be included in the accompanying minerals: Quaternary sands and gravels, tertiary sands and clays (Poznan clays). They are present in two colour variants in the Legnica deposit - and fiery. The mineral composition of greenish-blue clays allows them to be included in illite-kaolinite- smectite varieties, in turn fiery clays as kaolinite-illite-smectite varieties. The tertiary clays are a very useful raw material for the production of building materials. In addition, they are potential mineral sorbents due to the nature of the association of clay minerals (occurrence of montmorillonite). They also show suitability for building waterproofing barriers. Quaternary gravels and sands, developed in the overburden Legnica deposit are differentiated raw materials. Some of them are raw materials for the construction industry. The glacial tills can be used as a component of ceramic mixtures. Tertiary sands can be used as a proppant material. The information on the raw material properties of these sediments will be one of the essential criteria for their treatment as accompanying minerals. Minerals accompanying those developed in the Legnica deposit should be exploited and deposited selectively. The creation of anthropogenic deposits accumulating these minerals will provide the possibility of their use for decades after the termination of operation.
In the process of coal extraction, a fractured zone is developed in the overburden above the goaf. If
the fractured zone is connected with an aquifer, then water inrush may occur. Hence, research and analysis
of the height of overburden fractured zone (HOFZ) are of considerable significance. This study focuses
on the HOFZ determination in deep coal mining. First, general deformation failure characteristics of
overburden were discussed. Second, a new method, numerical simulation by orthogonal design(NSOD),
have been proposed to determinate the HOFZ in deep coal mining. Third, the validity of NSOD is verified
in the practical application, compared with empiric al formula in Chinese Regulations and in-situ test.
These three methods were applied to determine the HOFZ of working face No. 111303 in No. 5 coal
mine. The pre dicted HOFZ of NSOD is found to be similar to the result of the in-situ test (8.9% relative
error), whereas the HOFZ calculated by the empirical formula has extremely large error (25.7% relative
error). Results show that the NSOD can reliably predict the HOFZ in deep coal mining and reduce time
and expenses required for in-situ test.
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