Abstract
Opening deeper coal seams requires constructing underground mine roadways in difficult geological conditions. Supporting of such roadways is subjected to a very high load from the rock mass. The types of roof supports used so far do not provide immediate support for the rock mass, which tends to converge the roadway, allowing for a rapid build-up of stresses in the surrounding rock mass. The article presents a new type of frame roadway support. This is a yielding support (consecutive arches are connected in a helical pattern), enabling the successive arches to be provided with initial load-bearing capacity already at the construction stage. The so-called unscrewing of the helix enables the arches to be pressed against the surface of the developed roadway with a controlled force. The introduction discusses the types of yielding roof supports used in the Polish mining industry and indicates their characteristic features. Further along in the article, the assumptions adopted for the construction of models to be tested and assumptions for the static and dynamic load to the models are defined, and the results of the model numerical tests are presented. The tests were aimed at comparing the qualitative behavior of the new roof support and the closed, circular support which is closest to it. The results of numerical tests confirmed the strength of the new solution not lower than the closed (circular) frame support, previously used in the most difficult geological conditions.
Highlights
Mining the deeper coal seams in Poland means that the load to mine workings from the rock mass and the risk of rock bursts are systematically increasing
The main advantage of the discussed solution is the possibility of initial setting to load the support by “uncoiling” the helix formed of arched components, favorably affecting the co-operation of the support with the rock mass
According to the guidelines included in the standard [18], the roof support frames, in a yielding state were tested, until the height of support frames was reduced by 300 mm, as a result of a yield in joints
Summary
Mining the deeper coal seams in Poland means that the load to mine workings from the rock mass and the risk of rock bursts are systematically increasing In these conditions, the key issue is to ensure adequate stability of mine workings. As a result of exceeding the strength of rock layers, the floor is destroyed and heaved to the Energies 2021, 14, 5801. In underground mining plants, in the roadways and the areas of increased operating pressure, a yielding, steel frame support is used. Open, yielding, ŁP type frame support is mostly used to protect preparatory, newly developed or rebuilt roadways. The intensive process of the floor heave requires searching for new support solutions that will protect the roadway floor with sufficiently high load bearing capacity.
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