Piston mechanism of interaction of non-linear geomechanical and physicochemical gas exchange and mass transfer processes in coal-bearing rocks

Abstract

The article focuses on a theoretical and experimental framework for the quantification of interaction between nonlinear geomechnical and physicochemical processes in high-stress coal-bearing rock mass during mining under high seismic risk due to large-scale blasting and earthquakes, as well as because of structural and temperature effects. The tests were aimed to examine and study comprehensively the piston mechanism of gas exchange and mass transfer processes, revealed recently at the Institute of Mining, SB RAS, as well as to explain the fact that the earthquake-induced low-velocity (quasi-meter range) pendulum waves (velocity to 1 ​m/s and frequency of 0.5–5 ​Hz) could stimulate an increase in the gas content in coal mines. In order to perform laboratory investigation at the Institute of Mining SB RAS, special-purpose stand for analyzing gas exchange and mass transfer processes in coal-bearing geomaterials under various thermodynamic conditions (P, V, T) and gas composition was constructed in cooperation with the Institute of Semiconductors Physics SB RAS. Matching of air flow rate with compression pressures allowed to obtain relations showing that air flow rate increases at the uncertain time interval under the increasing of the compression pressure. The same measurements was carried out with another gases such as Hydrogen H₂, Helium He, methane CH₄, carbon dioxide CO₂ and carbon oxide CO. The laboratory tests aimed to detailed investigation of the previously revealed “piston mechanism” of gas exchange and mass transfer processes in the coal specimens and their quantitative description in terms of theory of the pendulum waves were carried in the first time. Consequently, there are some arguments for the testing of the opportunity of quantitative description of the “piston mechanism” related to gas exchange and mass transfer processes in the scale of coal mines. It is relevant when pendulum waves induced by powerful earthquakes and technical blasting reaches the mine.