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ArticleName Physico-mechanical substantiation of rock mass jetting in hydraulic borehole mining of placers
DOI 10.17580/gzh.2015.12.05
ArticleAuthor Bagazeev V. K., Valiev N. G., Simisinov D. I.

Ural State Mining University, Ekaterinburg, Russia:

V. K. Bagazeev, Professor, Doctor of Engineering Sciences,
N. G. Valiev, Vice-Principal for Science, Doctor of Engineering Sciences
D. I. Simisinov, Assistant Professor, Candidate of Engineering Sciences


The authors give theoretical substantiation and present analytical expressions for processes, technologies and basic parameters of water jetting at placers in loose and weakly cemented rock mass. Based on available classification of water jets (low-, medium- and high-pressure), depending on strength of rocks and initial water pressure at outlet of hydraulic jet, the analytical expressions are derived for dynamics of hydraulic jets and mechanism of rock destruction in holes depending on ultimate shear stress, cohesion, internal friction angle, deformation modulus, density, porosity and moisture content of rocks, initial water pressure and diameter of hydraulic jet. Most researches relate free jet dynamics and Re number of water jet, while axial pressure decrease for immersed jets is accepted irrespective of Re number and is characterized by a special turbulence factor. In the present study, the axial pressure decrease is considered as probable distribution of random values approximated by Person curves. The article presents formulas for: depth of ultimate stress zone induced in rock mass by hydraulic jet; specific water flow rate during clay soil washout; destructive load and maximum rock washout productivity. The derived analytical expressions allow finding optimal regimes and efficient parameters required for planning and application of hydraulic borehole mining, as well as bottom-line figures of specific water flow rate and washout productivity. The actual data on washout productivity and maximum washout radius are comparable with the calculation results.
The study was carried out under state assignment in the field of science, No. 2014/235.

keywords Placers, hydraulic borehole mining, physico-mechanical characteristics of rocks, hydraulic jet, water pressure, jet-bottomhole distance, analytical expressions, factors, water flow rate, washout productivity

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