Features of rock pressure manifestations with the slice pillarless extraction of the Third potash layer at the Starobin potash salt deposit

Rock pressure manifestations in the development workings and the bottomhole region of the lower longwalls with the slice pillarless extraction of the Third potash layer of the Starobin potash salt deposit were studied. The stability of the development workings and the bottomhole space of the longwalls and the nature of interaction of the bottomhole lining with the adjoining rocks were studied. The intensity of manifestations of rock pressure in the longwalls and the nature of roof subsidence of the bottomhole region and its fall behind the face support were assessed. The nature of the loading speed distribution of the bottomhole lining for the treatment cycle was clarified. The rate of change of the loading before the heading and during this process and the loading rate of the bottomhole lining are taken as the main load support indicators for the treatment cycle. The cyclical nature of the change in the magnitude of these indicators in the interval of 10–12 treatment cycles is revealed. Their dependence on elastic stresses and creep of roof rocks after the formation of a new face is shown. The presence of the dynamic component of the load of the bottomhole lining due to the factor of the speed of the bottomhole movement was established. The influence of the deformation of rocks in the troughs of displacement on the bottomhole lining has been established. At the same time, it is shown that over a time interval of more than 2 years, the intensity of deformation of the rocks is significantly reduced. The possibility is shown how to determine the mean spacing of the secondary rock subsidence of the main roof and to identify anomalies associated with the boundaries of tectonic dislocations, faults and subsidence troughs by analyzing the dynamics of the accumulated deviations from the average of load support indicators. Recommendations have been developed on rational and safe parameters for maintaining the bottomhole region and the development workings of the lower longwalls with the slice pillarless extraction of the Third potash layer.

Assessment and control of geodynamical risks under the conditions of a rock-bump hazardous complex deposit

Research has been carried out to study the peculiarities of rockbump hazards and induced seismic manifestations at the Nikolaevskoe deposit, and their close correlation with the tectonic structure of the rock massif has been established. In order to strengthen control over the rock-bump hazard in the TN-3 high-angle fault, in 2019 the observation network was expanded and continuous seismoacoustic monitoring of the rock mass at the deep levels of Nikolaevskoe deposit was organized. Monitoring data is verified by local geoacoustic method using the portable device “Prognoz L”. The results of the monitoring revealed major acoustically active zone with the main amount of seismic and acoustic events recorded during the last 5 years and occurring dynamic rock pressure manifestations. Nikolaevskoe deposit was the site of execution of the industrial experiment on regional discharge of a potentially rock-bump hazardous section of a shock blasting massif.

Rock Pressure Manifestation in Development Workings Advanced in a Thick Coal Seam

A research of rock pressure manifestations in the seam workings of seam 52 in “V. D. Yalevsky” mine is presented. It is shown that the inspected development workings advanced in a thick seam have a number of peculiarities determining the urgency of their stability research. It is noted that the researches are carried out in the workings subjected to coal extraction influence, as well as in the workings not subjected to that influence. A brief description of the research method including a visual examination of the mine workings and their support elements, instrumental studies of the border rock massif and the theoretical justification of the parameters of rock pressure are given. The following patterns: rock pressure manifestations mostly in the workings sidewalls, a positive time dynamics of rock pressure manifestations, and the increased intensity of manifestations in the workings roof after coal extracting in the face were recorded. The theoretical justification of rock pressure manifestations and the interpretation of the results of instrumental researches are given.

IRON ORE MINING GEOMECHANICAL PROBLEMS IN UKRAINE

The paper deals with problems in Ukrainian iron ore mining industry resulted from enterprises reaching deep levels of mining. There are also described main causes of hazardous situations due to geomechanical factors at such depths, dynamic forms of excessive rock pressure manifestations, and types of external factors affecting the state and behavior of load-bearing elements of mining and technological objects below the surface to enable mining operations. The paper provides recommendations on creating a specialized geomecanics support system for mining enterprises which is based on labour safety risk-management principles as well as it presents geomechanics tasks to be solved by the system.