Local reinforcing of footing supported in the destroyed rock massif
I. Sakhno1, O. Isayenkov2, S. Rodzin3
1Department of Mineral Deposits, Donetsk National Technical University, Pokrovsk, Ukraine
2Department of Geotechnology and Safety, Krasnoarmiisk Industrial Institute, Pokrovsk, Ukraine
3AGH University of Science and Technology, Krakow, Poland
Min. miner. depos. 2017, 11(1):9-16
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Purpose. Justification of feasibility of non-explosive destruction of hard rock during in-seam workings based on the obtained dependences related to changes of physical and mechanical properties of non-explosive destructive mixtures (NDM) in the process of hydration in borehole charges causing crack growth in the near-hole area.
Methods. Mine in-situ observations at gauge stations were used to determine dynamics of footing bulging. Photofixation method allowed to record discrete state of rocks in the footing during the repair works. The optimal layout for reinforcing the footing was developed in laboratory conditions on structural models by the analysis of longitudinal and transverse system deformations, and by studying the volume of rocks squeezed into the cavity simulating the working.
Findings. It has been experimentally proved that the footing rocks have a block discrete structure at a distance of at least half the width of inelastic deformations zone. The empirical dependences are obtained, describing footing bulg-ing and horizontal compaction of rocks under the influence of loading, as a result of the disturbance of the rocks equilibrium state by mining operations for consolidated and non-consolidated rocks.
Originality. Formation of a consolidated zone in the form of a straight prism with the vertex of its base triangle facing footing allows to reduce compaction of rocks under the mine by 20%, the footing bulging by 41.8%, and to decrease the volumes of rocks deformed in the working cavity by 41.5%.
Practical implications. The obtained results, with accuracy sufficient for practical application, can be used to develop new ways of ensuring stability of footing in cases when rocks have a high degree of destruction. The proposed scheme of local reinforcing, provided its parameters are theoretically justified, can be realized in mine workings with bulging to more than 500 mm. This will help slow the rate of footing deformations and improve the state of workings in difficult mining and geological conditions.
Keywords: rocks, destruction, pressure, stress, bulging
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