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The authors discuss conditions for sinkholes at ground surface after the active phase of potash mine flooding has been completed. The mathematical modeling shows that interconnected signs of sinkholing are localization of subsidence in a comparatively small area, high gradients of subsidence at the boundaries of this area and occurrence of a solution cavity to accommodate the caved volume. The research findings are promising in terms of adequate space-time prediction of dynamic failure of strata above flooded mines.

The Murmansk Region in the northeastern Baltic Shield has been for long assumed as aseismic. Initiated in the 1950s, the regular instrumental seismological studies allow new data on the essential increment in seismicity, demonstrated in the maps of the general seismic zoning of the territory of Russia (OSR-97). Powerful mining industry in the Murmansk Region also induces many seismic events. This article analyzes natural and induced seismicity and their cross-effect.

An elastoplastic problem is considered for elliptical, arched, square and polygonal cross-section tunnels on the assumption of Coulomb’s limit equilibrium and varied lateral earth pressure coefficients in intact rock mass. The problem is solved using the method of small parameters and the finite element method. The elastoplastic solutions are obtained for mutually influencing tunnels. The mechanisms of concentration of vertical stresses in a pillar established between mutually influencing tunnels are determined.

The study is devoted to effect of contact friction on failure, ultimate stress and moduli of elasticity in rock specimens under compression. It is found that dependence of the listed characteristics on friction coefficient is incremental. The author reveals zones of full contact and slide.

Transformation of the molecular structure of coal under long-term effect of confining pressure due to strain relaxation is estimated numerically. It is found that both under dynamic deformation, as has been determined earlier, and under relaxation of molecular structure of coal, atoms of methyl group and hydrogen remove from aliphatic fringe, join together and form molecules of methane. It is shown that these molecules immediately form sorbing-based connection with coal. Volumes of methane absorption generated in coal due to strain relaxation of the molecular structure of coal are calculated.

The article reviews in brief application of cyclical-and-continuous method in the conveyor-and-truck haulage in open pit mines. Consumption of materials and power is evaluated as a function of mined rock haulage volumes and depth of crush-and-reload station position in an open pit mine. The change in capital and operational cost to transport ore and hard overburden is studied at varied distances from a crush-and-reload station in open pit to a surface receiving station. Efficiency of the conveyor-and-truck haulage using cyclical-and-continuous method is evaluated. In terms of deep and large mineral deposits, the authors substantiate positions for crush-and-reload stations in large open pit mines.

The article reports the results of estimation of internal dump slope stability in flooded open pit coal mine Tamnava-West Field. The geostatic analysis of stability used methods by Bishop and Morgenstern-Price. The studies confirm that slopes of internal dump are sufficiently stable and sustain stability after drainage of the open pit.

The authors describe experiments on pretreatment of ore by injection of explosive gases before underground leaching of gold in mine conditions. It is shown that injection of explosive gases into opening micro-fractures enhanced efficiency of underground leaching owing to microstructural transformation of ore containing dispersed gold.

The study is focused on the existing methods of long directional borehole drilling in hard rocks in high-viscous oil and natural bitumen field development. The authors suggest improving the hard rock mass drilling process by combining percussion-rotary drilling and positioning systems.

The article describes bench tests and calculations aimed to determining effect of parameters of ring-type elastic valve on variation of average pressure in the valve clearance. The results allow refinement of the design model of ring-type elastic valve and correction of the elastic ring cross-section based on the determined mechanisms.