Abstract
The severe overburden failure induced by high-intensity mining is the essence of eco-environmental problems in Northwest China, and the degree of overburden failure is closely related to the location and failure of key strata (KS), which controls part of the strata in the overburden. In order to solve the problems of traditional KS based on mechanical parameters and numerical simulation methods that are time consuming, complex, expensive, and work intensive, it is necessary to find a simple and fast KS identification method. Based on the KS theory, which has been successfully applied in the field practice for nearly 30 years, and its current identification method by calculation or software, the magnetotelluric (MT) detection method was selected. According to the principle of MT detection method, the main influencing factors were analyzed. By summing up the relationship between the geological characteristics of the KS and its apparent resistivity (AR), the AR trends of ten kinds of lithology are given, and the identification mechanism of the MT detection method is revealed. Through the field measurement in Daliuta coalmine and the accuracy verification by the theory calculation, the KS obtained by the two methods are consistent. The results show that the MT detection method can be used to quickly identify the KS, and it is simple, convenient, and fast. It provides a reference for optimizing mining technology, mine pressure control, and mine precision.
Highlights
China is a large coal producer and energy consumer, which is mainly because coal is the primary energy source and provides the basis of the energy infrastructure necessary for long-term, rapid economic growth [1]
The relative error of 5% apparent resistivity (AR) is taken as the resolution standard; that is, when the relative error of overburden AR is greater than 5%, it will be regarded as a standard; that is, when the relative error of overburden AR is greater than 5%, it will be regarded as distinguishable anomaly
According to the characteristics of surface deformation and the key strata (KS) failure, the inflection point of surface subsidence curve is located at the boundary of goaf; the maximum surface subsidence is located at the middle of working face under the condition of horizontal coal seam
Summary
China is a large coal producer and energy consumer, which is mainly because coal is the primary energy source and provides the basis of the energy infrastructure necessary for long-term, rapid economic growth [1]. For the hard and thick strata, they may have a stronger bearing capacity, supporting those weak and thin strata that only act as loads. Based on these differences, the KS theory was proposed [11]. Of of 12 than two KS, as shown in Figure 1 [12], the top KS is named the primary KS (PKS), as it bears the entire load from Correspondingly, its roof to groundthe surface.
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