Ural State Mining University, Ekaterinburg, Russia:

V. K. Bagazeev, Professor, Doctor of Engineering Sciences, rmos.dep@ursmu.ru
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.

1. Britan I. V. Sostoyanie skvazhinnoy gidrodobychi. Krizis idei ili nedalnovidnost? (State of hydraulic borehole mining. Idea crisis or lack of foresight?). Nedropolzovanie XXI vek = Subsoil use XXI century. 2013. No. 6 (43). pp. 46–51.
2. Yang Lin, Tang Chuan-lin, Zhang Feng-hua. The technology of hydraulic borehole for underground mining and its application. Chinese Journal of Underground Space and Engineering. 2006. Vol. 4. pp. 662–665.
3. Shavlovskiy S. S. Osnovy dinamiki struy pri razrushenii gornogo massiva (Basis of jet dynamics during the rock massif breakage). Moscow : Nauka, 1979. 173 p.
4. Merzlyakov V. G., Baftalovskiy V. E. Fiziko-tekhnicheskie osnovy gidrostruynykh tekhnologiy v gornom proizvodstve (Physical-technical basis of water-jet technologies in mining production). Moscow : National Mining Research Center — A. A. Skochinsky Institute of Mining, 2004. 645 p.
5. Berezantsev V. G. Raschet prochnosti osnovaniy sooruzheniy (Strength calculation of foundation bed of structure). Moscow : Gosstroyizdat, 1960. 138 p.
6. Valiev N. G., Bagazeev V. K. Raschet parametrov ochistnoy vyemki peskov rossypey pri skvazhinno-gidravlicheskoy dobyche (Calculation of parameters of stoping of placer sands during the hydraulic borehole mining). Izvestiya vuzov. Gornyy zhurnal = Proceedings of universities. Mining Journal. 2012. No. 1. pp. 13–16.
7. Tsytovich N. A. Mekhanika gruntov (Mechanics of soils). Moscow : Vysshaya shkola, 1984. 288 p.
8. Popescu R., Deodatis G., Prévost J. H. Randomly heterogeneous soils under static and dynamic loads. Reliability-Based Design in Geotechnical Engineering: Computations and Applications. 2008. p. 224.
9. Arens V. Zh., Babichev N. I., Bashkatov A. D., Gridin O. M., Khrulev A. S. Skvazhinnaya gidrodobycha poleznykh iskopaemykh : uchebnoe posobie (Hydraulic borehole mining of minerals : tutorial). Moscow : Gornaya kniga, 2011. 160 p.
10. Yu-ying Zhang, Yong-wang Liu, Yi-ji Xu, Jian-hua Ren. Drilling characteristics of combinations of different high pressure jet nozzles. Journal of Hydrodynamics. Series B. 2011. Vol. 23, Iss. 3. pp. 384–390.
11. Arens V. Zh., Khrulev A. S. Experience of Hydraulic Borehole Mining from Deep-Seated Gold Placers. Journal of Mining Science. 2003. Vol. 39, Iss. 1. pp. 27–34.
12. Bartyshev A. V. Gidromonitornaya struya i model razrusheniya uglya (Water jet and coal breakage model). Gornyy informatsionno-analiticheskiy byulleten = Mining Informational-Analytical Bulletin. 2012. No. 6. pp. 5–13.
13. Arens V. Zh., Khcheyan G. Kh., Khrulev A. S. Metodika opytno-promyshlennykh issledovaniy tekhnologii skvazhinnoy gidrodobychi (Method of exprimental-industrial investigations of hydraulic borehole mining technology). Marksheyderskiy vestnik = Mine surveyor bulletin. 2010. No. 3. pp. 13–17.
14. Brenner V. A., Zhabin A. B., Shchegolevskiy M. M., Polyakov Al. V., Polyakov An. V. Sovershenstvovanie gidrostruynykh tekhnologiy v gornom proizvodstve (Improvement of water-jet technologies in mining). Moscow : Gornaya kniga, 2010. 343 p.
15. Cherney E. I., Babichev N. I., Sysoev V. N. et al. Modelirovanie protsessov razmyva zolotosoderzhashchikh peskov primenitelno k skvazhinnoy gidrodobyche (Modeling of erosion processes of gold-bearing sands as applied to hydraulic borehole mining). Kolyma = Kolyma journal. 1975. No. 3. pp. 7–9.