Shock-pulse transmission on driving metal tubes into the ground

Conclusions Analysis of the energy distribution in the transmission of a shock pulse to a metal tube through an intermediate element shows that the efficiency coefficient k_ef, the ratio of the energy in the head of the transmitted pulse to the impact energy, depends on parameters such as the mass and rigidity of the intermediate elements, the magnitude of the added mass, and the tube rigidity. If a circular plate is used as the intermediate element, then k_ef increases with increase in plate thickness until it is 0.2 of the tube diameter. Further increase in the plate thickness leads to increase in energy dissipation uncompensated by reduction in the striker recoil coefficient. The presence of an added mass reduces k_ef, on account of increase in both the energy dissipation and the recoil of the striker. Increasing the tube rigidity — for example, by increasing its cross-sectional area — reduces the efficiency of shockpulse transmission as a result of increase in the striker recoil coefficient and increase in the proportion of energy in the oscillating tail of the elastic pulse. It remains to thank E. N. Sher for useful discussions of the experimental results. Institute of Mining, Siberian Branch, Russian Academy of Sciences, Novosibirsk. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 1, pp. 89–97, January–February, 1998.     

Acoustic Emission of Coal in the Postlimiting Deformation State

The features of acoustic emission in coal samples in the state of pre- and postlimiting deformation are considered. It is shown that in the postlimiting deformation stages and in the transient period, a contrary change is observed in a correlation coefficient of the acoustic emission activity recorded in the upper and lower portions of a sample; whereas in the prelimiting deformation stages, this change is consistent. It is proposed to recognize the stages of deformation by the correlation coefficient of recorded in different zones: a positive coefficient corresponds to the prelimiting stage of deformation, and a negative one corresponds to the postlimiting stage. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 4, pp. 3–10, July–August, 2005.     

Impulsive liquid-gas fracture of brittle and ductile rocks and ways of improving the process

Conclusions 1. Other conditions being equal, an increase in the strength and fracture toughness of rock reduces mean crack velocity in impulsive hydraulic fracture and the final dimensions of the cracks within the loading-rate range 0.5·10⁹≤ ≤5·10⁹ Pa/sec. 2. Since the drag coefficient of fluid in a crack is determined by the roughness of the crack’s walls, other conditions being equal, the greatest effect from impulsive fracture should be seen in rocks with fine and cryptocrystalline structures. 3. If the coefficient that characterizes the degree to which a well is filled by combustible material is increased in value from 0.62 to 0.75, the dize of the disk-shaped tensile ruptures formed in ductile rocks increases 60–70%. 4. The main parameters characterizing the impulsive fracture of a productive bed (crack depth and width) depend more on the thermodynamic characteristics of the pressure generator in the well (injection time and pressure) than on the viscosity of the injected fluid. 5. A technology involving interval-by-interval impulsive fracture by sectional shaped charges of high explosives is recommended for strong brittle rocks of moderate and high density. Institute of Geophysics, National Academy of Sciences of the Ukraine (Kiev). Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 4, pp. 50–58, July–August, 1997.     

Character of strengthening of an initially orthotropic material when subjected to simple and complex loadings. Communication 1

Conclusions  We have carried out an experimental study of the inelastic properties of solids with simple and complex loadings, producing pure shear strains and the subsequent imposition of strain states of pure shear.

Geomechanical conditions for quasi-resonances in geomaterials and block media

Conclusions  Based on voluminous information about relations between the dimensions of the central zones of crustal earthquakes and various energy classes of underground explosions, as well as mine shocks and man-induced tremors, therefore, the hypothesis that we had previously advanced relative to the quasi-resonant mechanism of their manifestation is confirmed. Here, the geomechanical conditions for the development of quasi-resonances associated with the inducement of pendulum waves are characterized by the dimensionless energy criterion k:

Energy content of the nonexplosive excavation of rock by excavators with a dynamic scoop

Conclusions  

An approach to development of an information geomechanical structural model of the Kuznetsk coal basin

The geographic information system designed at the Institute of Coal and Coal Chemistry for the Kuznetsk Coal Basin and the non-linear geomechanics researches undertaken at the Institute of Mining has served the basis for analyzing the hierarchical structure of geological faults in the Anzherskiy economic district (Kemerovo Region). The analysis is performed by a new canonical scale for structural-hierarchical representations with base , where A and x are the normalized functionally related values). The recommendations are given on how to utilize the geoinformation system of the Kuznetsk Coal Basin in order to obtain a graphical-analytical representation and a system analysis of experimental geomechanical data. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 3, pp. 27–49 May–June, 2006.     

Environmental factors affecting geotextile filter design in coal refuse impoundments

The US Mine Safety and Health Administration (MSHA) issued the Second Edition of Engineering and Design Manual for Coal Refuse Disposal Facilities prepared by D'Appolonia in 2009. This second edition provides design guidance on the use of nonwoven geotextiles for drainage applications when replacing graded granular filters in coal waste impoundments. Coal refuse is susceptible to slaking that produces an increase in fine particles which may lead to geotextile clogging. This article presents the results of research which investigated the effects of slaking on the hydraulic conductivity of permeated refuse specimens in order to identify parameters influencing the design criterion for selecting candidate nonwoven geotextiles for drainage applications. Permeability tests were performed on refuse–geotextile samples at different compaction energies and varying moisture contents, followed by post-grain size distribution (GSD) tests. Conclusions indicate that (i) the k _soil of the acid-permeated refuse samples is one order of magnitude higher than the k _soil of the water-permeated refuse samples and was attributed to fine particle aggregation. Any potential increase in the k _soil due to continued particle aggregation may approach a failure criterion where the soil permeability is too high. The long-term effects of low-pH groundwater may cause an increase in refuse permeability, leading to criterion failure due to particle aggregation; (ii) comparisons of the coarse coal GSDs for the pre- and post-compacted, water-permeated specimens showed an increase in the production of particle fines due to slaking at critical indices.     

Nonlinear effects in the radiation and propagation of vibro-seismic signals in a rock mass

Results are presented from measurements of the vibro-seismic field of a surface source in a rock mass at depths of up to 1.5 km. Effects connected with the grouping of sources are examined along with the transformation of the signal spectrum during passage through an oil stratum. It is shown that the absorption coefficient of vibro-seismic monochromatic signals by sedimentary rocks is within the range 0.63–0.75 dB/λ_p, where λ_p is the length of the longitudinal waves. Institute of Mining, Siberian Branch, Russian Academy of Sciences, Novosibirsk. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 2, pp. 3–10, March–April, 1999.     

Microcracking of salt under creep

Conclusions During creep in rock salt samples, the concentration of microcracks decreases, due to their amalgamation and formation of larger cracks at rates proportional to the load. Moreover, the increase in the number of cracks, according to the acoustic emission and the electromagnetic radiation data, is the result of the formation of sub-micron cracks, which were undetected because of inadequate sensitivity and resolution of the microanalyzer. The parameters of the superimposed microcracking varied proportionally with the load and the duration of the tests. After 35 days under loads of 0.5 σ_c and 0.7 σ_c, the average crack length had increased by 29% and 50%. After 45 days, the increases were 42% and 54% (Fig 1). The average widths of the open cracks increased in the first case by 19% and 25%, and in the second, by 27% and 38%. The results can be used to evaluate the change in the void volume with time, as a result of expansion in rock salt deposits. G. V. Plekhanov Mining Institute, Leningrad. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 4, pp. 37–40, July–August, 1991.     

Use of technogenic and natural solutions in hydrometallurgical operations

Conclusions  The results obtained here demonstrate the promise of using technogenic and concentrated condensates of hightemperature heat carriers to perform leaching as part of the processing of copper-nickel ores. The productive solutions that were obtained have high contents of the useful components (grams and tens of grams per liter) and could be converted to the desired end products by proven methods [12]. The following problems should be addressed first in future research in this area:

Specifics of the sulfuric-acid processing of galena concentrates in the presence of nitrous acid

Conclusions  

The adoption and adaptation of passive treatment technologies for mine waters in the United Kingdom

During the 1990s, passive treatment technology was introduced to the United Kingdom (UK). Early hesitancy on the part of regulators and practitioners was rapidly overcome, at least for net-alkaline mine waters, so that passive treatment is now the technology of choice for the long-term remediation of such discharges, wherever land availability is not unduly limiting. Six types of passive systems are now being used in the UK for mine water treatment: