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The implementation stages of ground laser scanning of an open pit field and the obtained data processing in Maptek I-Site Studio are discussed as a case-study of Kentobe open pit mine of iron ore. The procedure of a digital geological-geomechanical model is described; the framework is a set of spatial points obtained from the laser scanning. The model enables a detailed study of geological structure of the pitwall rock mass, with regard to the structure and tectonics, as well as the physical and mechanical properties of rocks. Using the developed model, the authors estimated the pitwall stability and substantiated safe slope parameters for deeper mining.

To predict uniaxial compressive strength using the indirect techniques of the Schmidt hammer rebound number (N) and Point Load Index (PLI), it is required to have valid empirical equations based on rock types. This study is an attempt to address this issue by developing a model that is valid for various rock types. Three models, i.e. linear, power and quadratic, were tested on each rock type (sedimentary, ingenious and metamorphic). The highest correlation was achieved by the quadratic model. The generalized model showed the lowest correlation as against the individual models.

The authors estimate stress state in the support system and in rocks nearby a roadway driven in unstable rock mass and when the voids and cavities in the roadway roof are filled with hardening foam. The calculation includes an assumption that the support system, rocks and the hardening foam deform elastically. The stress distribution in the support system is determined at different heights of the rock cavity in the roof rocks in the roadway and at different initial stress state of rocks. The zones of potentially hazardous stress concentration in the support system are identified.

The article describes the lab-scale testing data on acoustic and seismic emission generated in hydraulic fracturing of a cement block under volumetric loading by nonequal stresses. The connection of the acoustic and seismic emission with the rate of injection of power fluid and the change in the fluid pressure in the course of the fracture initiation, growth and arrest is demonstrated. The authors recommend on improvement of receiving equipment and on using the research findings in the hydraulic fracturing control.

This study focuses on an impact wave generated in a uniaxially compressed granite sample by a pendulum hammer in the direction transversal to compression. The pressure was varied from zero to a pre-destructive value. Microcracking during impacts was recorded using the method of acoustic emission (AE). The energy distribution in the time series of AE pulses followed an exponential law both in the unloaded and in the statically loaded samples. The first impacts induced local damage with a splash in AE from small cracks which, under subsequent impacts, coalesced and initiated redistribution of larger microdamages. In generation of an impact wave in a sample under pre-limiting compression, the surface of the induced main crack exceeds the area of the local damages by a few orders of magnitude, which is typical of the trigger effects which lead to large-scale fractures under external impacts at a safe-density energy.

The scope of the experimental research embraces velocities of elastic waves in rock samples before and after formation of a horizontal main crack. In undamaged samples, there is no essential change in the elastic wave velocity as the axial pressure increases from 0 to 20 MPa. The main crack having its surfaces approaching gradually leads to the increase in the elastic wave velocity. Aimed to improve sensibility of kinematic ultrasonic parameters relative to mechanical stresses, the coda wave interferometry algorithm is implemented as an analysis of times of the first arrivals of multiply scattered waves. With the mentioned algorithm, sensibility of the ultrasonic control grows considerably even in uniform samples.

The article describes the decision-making concept for the systemic blasting in open pit mining at structurally complex mineral deposits. The authors discuss approaches to determining allowable seismic impact in rocks having different strength characteristics.

The article describes semi-commercial testing of different technologies and facilities which ensure the required level of mining efficiency and quality of diamond-bearing ore. The use of the column charge explosives with radial clearance and air-split emulsion explosives allows stress state control in rock mass and reduces zones of high risk of crystal damage. The chain charge explosives appear to be a clever engineering idea for difficult mining conditions. The authors review the modern methods of drilling-and-blasting at mining sites of ALROSA.

The seismic activity in undermined rock mass in a mine at the Khibiny Massif is analyzed over the period from 2008 to 2020. The influences on deformation, tensile fracturing and caving in undermined rock mass are revealed. Three zones of deformation of different nature and velocity are identified in undermined rock mass in Kirov Mine: the zone at the juncture of underground and opencast mining; the zone of overhanging rocks; the zone of two- and three-side buttress at the edges of operating deposits. It is found that mining with head-on fronts, with formation of a support pillar and with overhanging of an uncaved rock mass beam is adverse. The pillar collapses later on and deformation of the pillar-supported rock mass during breaking of the butt section on sublevels occurs in the dynamic mode with high seismic activity both in terms of the number of seismic events and their energy emission. It is found that the width of the seismic activity band and the caving pitch of the overhang depend on the height of undermined rock mass.

The authors review the application range and parameters of internal dumping in open pit mining of brachysyncline-type coalfields. Specifics of the technology is described. The factors that govern the volume of internal dumping are identified. The possible ways of increasing the volume of internal dumping are shown. The methods and means for increasing the intake capacity of internal dumps are revealed. The ecological and economic advantages of internal dumping are discussed.