Estimation of critical depth of deposits by rock bump hazard condition

The paper proposes a theoretical method for determining the critical depth for classifying a deposit as liable to rock bumps. A formula for determining the critical depth of the rock bump hazard condition is obtained. A mathematical analysis of the influence of the physical and technical parameters of the formula on the critical depth is carried ou

Effect of geological and geophysical characteristics of complex-structure ferruginous quartzite ore bodies on blasting and processing performance

In terms of the complex-structure ferruginous quartzite ore body mining in the Kursk Magnetic Anomaly, the authors validate the requirement to account for anisotropy of rocks with a view to improving performance of preparatory and blasting operations, stabilizing grain size composition, reducing production of oversizes, saving energy input of milling, enhancing useful component extraction into concentrate and decreasing losses with regard to the sound subsoil management condition

Blasting methods of stress state determination in rock mass

The methods for the determination of stress state in rock mass using the energy of explosion are substantiated. The industrial tests are performed with a view to sizing zones of squeezing and radial fracturing in mines of Priargunsky Mining and Chemical Works. It is found that the fracturing zone radius decreases and the squeezing zone diameter increases with the grater depth of mining operations. The theoretical formulas for calculating stresses depending on sizes of squeezing and fracturing zones, physical and mechanical properties of rocks and detonation characteristics of explosives are obtaine

Geomechanical behavior of jointed rock mass in the large-scale blast impact zone

The review of literature sources has allowed determining the mechanism of seismic blasts waves in jointed rock mass. The author presents the theoretical formulas for calculating stresses, relative strains and displacement velocities induced in rock mass by large-scale blasts. The formulas take into account the detonation characteristics of explosives, the borehole diameter, the length of explosive charges, the number of simultaneously blasted charges per groups and the factor of explosion energy redistribution to rock throw. Moreover, the formulas include the properties of rocks between the blasting point and a guarded object, and on the exposed surface of a guarded objec

Seismically safe parameters of confined blasting in levelling dry dock bottom

During construction of a dry dock, it became necessary to level the bottom of gneissic granite rock mass to 7 m by blastin

Effect of geological and geophysical characteristics of complex-structure ferruginous quartzite ore bodies on blasting and processing performance

In terms of the complex-structure ferruginous quartzite ore body mining in the Kursk Magnetic Anomaly, the authors validate the requirement to account for anisotropy of rocks with a view to improving performance of preparatory and blasting operations, stabilizing grain size composition, reducing production of oversizes, saving energy input of milling, enhancing useful component extraction into concentrate and decreasing losses with regard to the sound subsoil management condition

Blasting methods of stress state determination in rock mass

The methods for the determination of stress state in rock mass using the energy of explosion are substantiated. The industrial tests are performed with a view to sizing zones of squeezing and radial fracturing in mines of Priargunsky Mining and Chemical Works. It is found that the fracturing zone radius decreases and the squeezing zone diameter increases with the grater depth of mining operations. The theoretical formulas for calculating stresses depending on sizes of squeezing and fracturing zones, physical and mechanical properties of rocks and detonation characteristics of explosives are obtaine

Substantiation of strength of the filling mass by taking a blast effect into account for the room-and-pillar methods

The development of the uranium ore bodies at the ore mines of PJSC «Priargunsky Industrial Mining and Chemical Union» (PJSC «PIMCU») by room-and-pillar method as high as a pillar between the levels (60 m) without fill, as a rule, leads to the fall of the adjoining rock, to the strong contamination of the ore and to the high yield of the oversize pieces of the barren rock. A longstanding industrial and theoretical research shows that the sizes of the self-sustaining rock escarpments at the ore mines of PJSC «PIMCU» in the solid mass of trachydacites, conglomerates, sandstones, felsites are equal to 20-40 m. Moreover, the sizes of the self-sustaining rock escarpments depend to a great extent on the intensity of fracturing of the adjoining rocks. The stable size of the escarpment does not exceed 5-10 m for the rocks with the size of a jointing up to 0.05 m. Consequently, timely performance of the filling operations of the worked-out space of the chamber is important. However, the question then arises: which characteristic strength should the filling mass have? The calculations of the characteristics of the filling mass in compliance with the reference guide «Shaft filling operations» show underestimated values of the characteristic compressive strength of the fill (1.4 MPa) for the room-and-pillar method, which leads to the increase of the ore contamination by the fill and provokes the additional costs for refilling of the volumes of the rock fall. On the basis of the Russian experience of using of the consolidated fill for the development of the ore bodies of 15 m thickness by chamber method the strength of the fill is taken as 3-5 MPa under the resultant value of the static stresses without taking into account the character of the dynamic loading stresses induced by the sequence blasthole ring initiating in a chamber. Overestimating the characteristic strength of the filling mass results in the high consumption of the cementing materials. On the basis of the theoretical research the authors suggested the theoretical dependence of calculation of the characteristic strength of the filling material with respect to compressive stresses of the fill induced by the blasting operations. The process of designing of the filling mass with the zones of diverse strength for the room-and-pillar extraction with the consolidated rock fill is proven to be economically reasonable. The bottom zone of the solid mass should have high strength (3-4 MPa), and the strength of the upper zone should be up to 2-2.5 MPa