Mirny Polytechnic Institute (Division), Ammosov North-Eastern Federal University, Mirny, Russia:

I. V. Zyryanov, Head of a Chair, Professor, Doctor of Engineering Sciences

Yakutniproalmaz Institute, ALROSA, Mirny, Russia

A. N. Akishev, Head of a Department, Candidate of Engineering Sciences, akishevan@alrosa.ru
I. B. Bokiy, Head of a Laboratory, Candidate of Physical and Mathematical Sciences
N. M. Sherstyuk, I CAT Engineer

A specific feature of open pit mining of diamond deposits in Western Yakutia is the construction of the open pits in the zone of negative ambient temperatures, which includes thick permafrost rock mass, and which is at the same time complicated by the influence of cryogenic processes on deformation of pit wall benches. The paper presents the comparative analysis of strength characteristics in frozen and thawed rocks, stability of benches during mining, the general geomechanical approach to the determination of parameters of non-mining walls of the ultra-deep open pit diamond mines, and the parameters of nonmining walls and benches. Optimization of open pit wall configuration should primarily be based on the maximum utilization of the strength properties of frozen rocks in combination with the development of new approaches, calculation schemes and methods for assessing stability of open pit walls and benches of unconventional design, including the non-mining vertical benches. The main design characteristic that determines the parameters of open pit walls is the structural tectonic relaxation coefficient, which specifies the calculated value of cohesion in rock mass. For the diamond deposits, the values of the structural relaxation coefficient were obtained in a series of field tests and back calculations. Full-scale tests were carried out both during exploration operations in underground mines and in open pits. The accuracy of determining the values of the structural relaxation coefficient in the range of 0.085–0.11 is confirmed by the parameters of non-mining walls in an open pit mine 385–640 m deep, with overall slope angles of 38–55° and a steeper H 0.35–0.5 lower part having the slope angle of up to 70° with average strength characteristics of 7.85–11.84 MPa and the internal friction angle of 28.1–37.4°. Using the natural load-bearing capacity of rock mass to the full advantage, which the values of the structural relaxation coefficient of deposits show, allows optimization of open pit wall slope design and minimization of stripping operations.

1. Glozman G. R. Analysis and prevention of deformations of slope composed of permafrost rocks : thesis of inauguration of Dissertation … of Candidate of Engineering Sciences. Leningrad, 1968. 26 p.
2. Rozenbaum M. A. Geomechanical framework for the ground control in coal mining in the permafrost zone : Dissertation … of Doctor of Engineering Sciences. Saint-Petersburg, 1996. 363 p.
3. Ermakov I. I. Analysis of slope stability in round and oval pits in the conditions of permafrost rocks : A case-study of Mir kimberlite pipe : Dissertation … of Candidate of Engineering Sciences. Leningrad, 1965. 150 p.
4. Kozeev A. A., Izakson V. Yu., Zvonarev N. K. Thermo- and geomechanics of diamond deposits. Novosibirsk : Nauka, 1995. 243 p.
5. Guidelines on determination of slope angles for benches and pit walls composed of permafrost rocks. Leningrad : VNIMI, 1972. 106 p.
6. Rules of slope stability provision on coal strip mines. Saint-Petersburg : VNIMI, 1998. 208 p.
7. Zakharov V. N., Rylnikova M. V., Nikiforova I. L. Development of scientific and methodological foundations for the design of mining systems in open pit development. GIAB. 2017. Special Issue 37. Open pit mining in the 21^st century : Results, problems, potential growth prospects-1. pp. 13–26.
8. Zoteev V. G., Zoteev O. V. About necessity of improvement of standard&methodical base on geomechanical security of open mining work. Gornyi Zhurnal. 2010. No. 1. pp. 66–68.
9. Rylnikova M. V., Zoteev O. V., Nikiforova I. L. Development of the regulatory framework to provide the stability of pitwalls and benches of quarries, opencast mines and spoil dumps. Gornaya promyshlennost. 2018. No. 3. pp. 95–98.
10. Tsirel S. V., Pavlovich A. A. Challenges and advancement in geomechanical justification of pit wall designs. Gornyi Zhurnal. 2017. No. 7. pp. 39–45. DOI: 10.17580/gzh.2017.07.07
11. Zhabko A. V. Theory of calculation of slopes and grounds stability. analysis, characterization and classification of existing metho ds for calculating the slopes stability. Izvestiya Uralskogo gosudarstvennogo gornogo universiteta. 2015. No. 4(40). pp. 45–57.
12. Read J., Stacey P. Guidelines for open pit slope design. Collingwood : CSIRO Publishing, 2009. 487 p.
13. Chaoyi Sun, Congxin Chen, Yun Zheng, Kaizong Xia, Wei Zhang. Topping Failure Analysis of Anti-Dip Bedding Rock Slopes Subjected to Crest Loads. International Journal of Geotechnical and Geological Engineering. 2018. Vol. 12, No. 11. pp. 685–693.
14. Yun Zheng, Congxin Chen, Tingting Liu, Kaizong Xia, Xiumin Liu. Stability analysis of rock slopes against sliding or flexural-toppling failure. Bulletin of Engineering Geology and the Environment. 2018. No. 4. DOI: 10.1007/s10064-017-1062-z
15. Bar N., Barton N. The Q-Slope Method for Rock Slope Engineering. Rock Mechanics and Rock Engineering. 2017. Vol. 50, Iss. 12. pp. 3307–3322.
16. Azhari A., Ozbay U. Investigating the effect of earthquakes on open pit mine slopes. International Journal of Rock Mechanics and Mining Sciences. 2017. Vol. 100. pp. 218–228.
17. Pustovoytova T. K., Gurin A. N., Kagermazova S. V. Slope stability in permafrost rock masses. VNIMI Transactions : Collected papers. Leningrad, 1980. pp. 101–105.
18. Akishev A. N., Bokiy I. B., Zyryanov I. V. On the development of geotechnology for open-cast mining of diamond deposits. Mining technology improvement and personnel training toward the the technosphere safety in the north-east of Russia : Proceedings of All-Russian Conference with International Participation on the Occasion of Professor E. N. Chemezov’s 80^th Anniversary. Yakutsk, 2018. pp. 267–274.
19. Zyryanov I. V., Akishev A. N., Bokiy I. B., Bondarenko I. F. Innovations in diamond mine planning in a permafrost zone. Gornaya promyshlennost. 2018. No. 5. pp. 66–69.
20. Akishev A. N., Bokiy I. B. To the issue about possibility of increasing an open pit slope angle in conditions of a cryolithozone. GIAB. 2014. No. 8. pp. 36–40.