Vol 53, No 3 (2017)

The analytical estimates of stress state of surrounding rock mass around underground openings neglect the overlying strata weight, which results in the disagreement between the calculated and in situ measured displacements. The authors propose the phenomenological theory of deformation in order to eliminate the mentioned inconsistency. The theory is based on the fact that the direction of the roof rock weight load coincides with the orientation of tensile stresses found in an auxiliary problem. The authors introduce a parameter characterizing ratio of roof rock displacements to floor rock displacements, which allows solving inverse problems using the basic supplement—in situ measured displacements in the floor and roof rocks.

The performed thermobaric tests of cylindrical bazhenite specimens consisted in recording of time variation in height of the specimens, h(t), under constant axial loading at varied temperature T. The authors demonstrate that under rapid increase/decrease in T deformation process obeys the thermoelastic law and calculate the coefficient of linear temperature expansion. Under constant increased temperature, the process of deformation is described using the viscoelastic Voigt model. The authors formulate and solve inverse problems on elastic moduli and viscosity of rocks by the data of h(t).

Engineering formulas for the new-way determination of the degree of loading are obtained using the procedure of averaging stress state of pillars having different relative heights. The article presents quantitative estimates of the classical and proposed ways to determine the degree of loading of wide (stiff) and narrow (yielding) pillars. The scope of the study encompasses the influence of a ground surface trough and an upland area on the rock pressure value at the level of pillars, included in the expression for the determination of the degree of loading.

The study shows that in electropulse drilling, an increment in energy deposition into the discharge channel results in the linear increase in the drilling rate that grows with the spacing of electrodes. The energy consumption due to energy deposition undergoes a minimal change, while the size of cuttings is conditioned by the energy deposition and spacing of electrodes.

In focus is improvement of hole-making technology by vibro hammer pushing with batch-wise removal of soil core while a pipe is driven in soil under impact loading. The important advantage of the technology is the concurrent pipe driving and soil core removal. The minimal air pressure required to separate a core and transport it along the pipe is determined. The frequency of soil core separation and transport during vibro-hammer driving of pipes in soil has been tested in underground construction of utilities. The tests prove the possibility to cut-down time of trenchless construction of underground passages and to raise the level of mechanization of the operations.

The discussed basic features of geology of gold placers in Transbaikalia include: long extent, occurrence of a gold pay streak nearby gutter, small thickness of a gold pay streak and deep occurrence sometimes, majority of fine flattened gold particles. It is suggested to enhance development of such placers using new engineering solutions. It is recommended to carry out flushing by means of technologies based on the combination of flotation and gravity concentration followed by activation leaching of gold from concentrates and bullion minerals–gold concentrators. A new leaching technology offered for deep-seated placers involves pre-drainage of a pay streak, saturation of the pay streak with photoelectron-activated concentrated solutions and, finally, electrodiffusion leaching of gold.

One of the approaches to reducing aftereffects of rock bursts is the dynamic support capable to stand strong dynamic rock pressure events in the form of seismic vibration and failure of adjacent rock mass. The article describes the support design procedure in use in hard mineral mines exposed to rockburst hazard. Different types of rock bolting and surface support are discussed from the viewpoint of energy absorption and yielding.

In focus is waste management—utilization of screenings after volcanic rock crushing at broken stone production plants. The authors formulate causes of increased production of screenings and their poor utilization. The composition and properties of screenings of granite, gabbro and hornblendite are determined. High content of dust particles limits the use of screenings in production of concrete and mortar. It is proposed to remove dust from screenings by pneumatic treatment. The test data on air separation of screenings by cross-flow classifier are reported. The efficiency of dry processing of screenings is checked in tests of treated sand behavior in composition of heavy concrete. It is shown that treated sand enhances strength of concrete.

The authors discuss the mechanism of interaction between dust coal and gas flow. The characteristics of two-phase flow are studied with regard to energy of expanding gas at the stage of outburst propagation using the developed method of numerical modeling. The mechano-mathematical method is verified in the wind tunnel tests of dust coal and gas flow. The comparison of the experimental and modeling data show satisfactory agreement in description of two-phase coal dust and gas flow under outburst with formation of shock waves attenuating in the line of the flow. The volume concentration of dust coal in two-phase flow essentially influences the process of the outburst shock wave attenuation.

The article reports test data on adsorption and flotation characteristics of thermomorphic polymer joined with diphenylphosphine—TMPD. The test materials are natural pyrite and arsenopyrite, and models of gold-bearing sulfide minerals. Electron microscopy and X-ray structure analysis prove that reductive adsorption of gold at the surface of sulfide minerals from HAuCl₄ solution allows modeling natural aggregates of sulfides and finely dispersed gold. UV spectrophotometry proves selective adsorption of TMPD at gold. Laser scanning microscopy shows connection of TMPD with micro- and nano-size gold on polished sections of pyrite and arsenopyrite. During monomineral flotation, joint use of TMPD and butyl xanthate at a ratio of 1:1 doubles the yield of gold-bearing sulfides and enables maximum recovery of gold minerals at the total consumption of reagents reduced by 30–50%. It is found that TMPD is selective relative to gold-bearing minerals and its combination with xanthate ensures a considerable increment in gold-bearing mineral recovery by flotation.

The article demonstrates feasibility of additional iron recovery from the secondary kind of mineral raw materials—dry magnetic separation tailings obtained at crushing and processing factories of Abaza and Irba and wet magnetic separation tailing produced at Abagur processing plant of Evrazruda. Dry centrifugal separation treatment of Abaza tailings–3 mm in size allowed 6.3% of middlings with Fe_total and Fe_mag contents of 40.4 and 32%, respectively; the result of dry magnetic separation of Irba tailings -5 mm in size is 7.7% middlings with the content of Fe_total and Fe_mag 39.9 and 30.8%. Wet magnetic separation of Abagur tailings -0.007 mm in size allowed recovery of 0.6 to 1.45% of magnetic fraction with Fe_total content of 53.3 and 51.6%, respectively, and Fe_mag content of 49.8 and 48.5%. Fitting of modern separators with the magnetic systems based on neodymium–ferrum–boron considerably improves output of the machines (in dry centrifugal separation circuit) and enhances the yield of magnetic product in wet separation of tailings.

The process of coal suspension dewatering in centrifuges and pneumatic drainage in vacuum filters and filter presses is theoretically studied. From the condition of equal centrifugal forces and surface tension applied to liquid in a granular layer of the working element of the centrifuge bowl, the analytical relation is obtained to calculate residual concentration of liquid in the treated layer. It is shown that calculation results obtained using the relation, rated data and specifications of industrial drainers agree well. With regard to the equality between the kinetic energy applied by filtration flow in the granular layer to the liquid film in the granules and the work to overcome surface tension forces that keep the film on the surface of the granules, the analytical relation is obtained to calculate residual concentration of a liquid in the layer under pneumatic drainage. The estimates prove realistic nature of the results obtained with the latter relation as well as their agreement with the test and rated data of industrial vacuum filters and filter presses.

The developed geoinformation technology based on the experimental and computer-aided physicochemical modeling enables quantitative calculation and mapping of aftereffects of geochemical processes in sulfide material dumps in terms of Udokan copper deposit. The role of nitrogen as a component of acid rains is emphasized together with its effect on chemical weathering of sulfides. The authors report modeling and testing data on oxidative leaching of Udokan sulfide ore using nitrogen compounds. The classical and geoinformation approaches to calculating leakage flux being of importance for exploration and geoecology studies in permafrost are compared. The obtained results on intensification of sulfide oxidation under conditions of permafrost allow estimating potential environmental impact of the planned mining operations at Udokan deposit and can be used to improve the current cryo-geotechnologies of metal ore mining.

The authors have designed a multi-purpose multi-channel data recording and transmission system for the laser strainmeters and the related geophysical and seismic equipment intended for service in operating mines.

In the published version there is an error in the initials of an author. The present form in this erratum is the correct: A. S. Voznesensky.