The hypothesis of the piston effect during mine gas migration caused by fault reactivation was studied, with the use of computer modeling, to explain cases of a sudden appearance of mine gases on the earth surface in coal mining areas. The study is based on the factual data of the mode and amplitudes of subsidence along faults during mining, the morphology of the fault planes, and the theoretical ideas about the discrete nature of the fault wall displacement along uneven contact surfaces. It is taken into account that the walls of the fault, due to the asperity types “ridge” and “sag”, form contacts of the “ridge–ridge” and “ridge–sag” patterns. This study examines the situation where gas pressure in the fracture space can sharply increase due to the jerky displacement of reactivated tectonic fault walls with a rough fault plane. It is assumed that, in the first phase of reactivation, the fracture space expands as a result of the displacer opening and the fact that fault plane asperities engage in the “ridge–ridge” type of contact. With the subsequent relative displacement of the fault walls in the second phase of reactivation, the contact changes into the “ridge–sag” type and a sharp reduction in the fracture space volume occurs. It is shown that a “piston effect” emerges due to the reduction in fracture space and that it promotes an increase in gas pressure and stimulates gas movement to the surface through the available channels. The resulting “piston effects” may also be responsible for the suddenly raised gas content recorded in the air of surface structures and recurrent mine gas migration onto the surface. The findings expand our understanding of the sudden gasification of the earth surface and living spaces in coal mining areas and contribute to the understanding of the gas migration process, thereby helping to monitor hazards.

The paper investigates the hypothesis according to which one of the factors influencing the spontaneous combustion of coal-bearing dumps is its geodynamic position, i.e. its location in the geodynamically dangerous zone (GDZ) at the boundary of the Earth crust blocks. This hypothesis is put forward on the basis of scientific ideas about the block structure of the Earth crust and the available statistical data on the location of burning dumps and is studied using computer modeling. A dump located in the area of Eastern Donbass was chosen as the object of research. The simulation results show that the penetration of air into the dump body from the mine through the GDZ, which crosses the mining zone, is possible at an excess pressure of 1000 Pa created by the main ventilation fans. The fire source appearance in the dump body causes an increase in the temperature of the dump mass and becomes a kind of trigger that "turns on" the aerodynamic connection between the dump and the environment, carried out through the GDZ. It is concluded that the establishment of an aerodynamic connection between the mine workings and the dump through the GDZ can be an important factor contributing to the endogenous fire hazard of coal-bearing dumps. The simulation results can be used in the development of projects for monitoring coal-bearing dumps and measures to combat their spontaneous combustion.

The paper proposes a mathematical model, based on a one-dimensional nonhomogeneous diffusion equation, which enables the evaluation of methane emissions from extracted coal during its transportation through the haulage system of a coal mine longwall face and their contribution to spatiotemporal distribution patterns of mine atmospheric parameters characterizing the gas environment in the face area. The solution to the specified equation has been implemented using the Mathcad computational software package. The results of numerical experiments demonstrate potential applicability for enhancing operational efficiency in managing technological processes within the boundaries of the longwall face.

From the experience of coal mining, there are known cases of gas emissions into mine workings and onto the surface, the volumes of which greatly exceed the calculated expected values. In this work, we link the intensification of gas emissions to mining workings with the process of transition of the coal strata deep sections to a critically stressed state, which is accompanied by deformation of the rock mass and is recorded by seismic activity. Seismic activity at depths exceeding the depths of mining operations has now been detected at many deposits by means of seismological monitoring. On this basis, we accept the working hypothesis that the evolution of the critically stressed state of the earth's crust in areas of mining operations manifests itself as its spread to ever deeper horizons. As the area of mining operations increases, this process proceeds from top to bottom, covering ever deeper horizons of the earth's crust, accompanied by fracture formation, contributing to their degassing and the flow of gases into mine workings from deep parts of the subsoil. Computer modelling illustrates how an increase in rock-mass permeability may facilitate gas migration from deeper horizons towards mine workings and the surface. The model provides a simplified representation of the proposed mechanism under the adopted assumptions. Using the situation in Kuzbass as a case study, the paper demonstrates a gradual increase in the depth of seismic activity manifestation, reaching depths of 5–6 km beneath the Bachat open‑pit mine. The scenario‑based methane‑volume estimate indicates the possibility of methane migration from depths of several kilometres, with quantities comparable to the emissions from the seams recently under development. The results support consideration of this mechanism as a possible explanation for reported gas anomalies in Kuzbass mining areas.