In the development of practically all potash salt deposits, the study of gas-dynamic phenomena (GDP) is one of the most difficult tasks to ensure mining safety. Sudden salt and gas outbursts, dynamic breakdown, which are accompanied by intense gas release and possible broken rock carry-over into the mine workings, are associated with GDP. Geological preconditions for the GDP development are often the layered structure of the salt rock mass, the presence of interlayers and layers of salt clays. For the conditions of the Usolsky potash plant mine, complex studies of factors that characterize the possibility of gas-dynamic roof fall of the stoping rooms were carried out. In mine studies, free gases pressure and the initial velocity of gas release in the rocks of the roof workings were determined. The obtained experimental estimations were used as a parametric basis for mathematical modeling of geomechanical processes under conditions of a near-contact accumulation of free gas. The deformation of a layered salt mass produced by a room development system was described by the model of an ideal elastic-plastic medium with internal friction. The parabolic envelope of Mohr circles was used as a plasticity criterion in the compression area. In the numerical implementation, the deformation of clay contacts was modeled by Goodman contact elements. Based on the results of multivariate numerical calculations, it is established that the main factors determining the possibility of implementing GDP are the additional gas pressure at the contact, the width of the workingspan, and the distance from the roof to the first gas-containing contact. With multi-level lamination of roof rocks, there is a danger of large sources of GDP formation and the mechanism of successive fall of layers in an instant mode is implemented.
Radiation seismic tomography is used in seismic exploration as one of the data interpretation techniques. It can be used to reconstruct a detailed picture of the rock structure in the space between two mine workings. The spatial distribution of attenuation or velocity of elastic waves is calculated using linear integrals or their approximations along the rays and reproduced digitally. The solution of large systems of linear equations linking the measured integral parameters and characteristics of the studied geological objects is performed using various algebraic algorithms. The analysis of elastic wave propagation between excavations is based on the concepts of geometrical optics. The possibilities of the reconstruction algorithms are illustrated in the process of processing experimental results of mine studies. The method allows to reproduce two-dimensional distribution of variations of the studied parameters.
