Mining Institute, Perm Federal Research Center, Ural Branch, Russian Academy of Sciences, Perm, Russia:

V. A. Asanov, Head of Laboratory, Doctor of Engineering Sciences, ava@mi-perm.ru
A. V. Evseev, Researcher, Candidate of Engineering Sciences
I. L. Pankov, Senior Researcher, Candidate of Engineering Sciences
V. N. Toksarov, Senior Researcher, Candidate of Engineering Sciences

Safety of underground mining of water-soluble minerals depends in many ways on the deformation dynamics in load-bearing elements of a mining system. According to the analysis of the condition of stopes in mines at the Upper Kama Potash Deposit, the roof of stopes in many instances looses stability prior to expiration of the stope life time set in accordance with the technological conditions of mine operation, which elevates the risk of failure of rib pillars and discontinuity of impermeable strata. The article discusses the lab-scale and full-scale research data on deformation and failure of elements (rib pillars and partings) in the system of open stoping in sylvinite seams. The research findings are used to adjust mathematical model of stress state of undermined salt rocks. The extensive examination of physical and mechanical properties of salt rocks under different loading conditions shows that clay partings and very poor quality of rock mass are most best pronounced in indexes of clay and salt rock deformation, which has made it possible to develop an estimation procedure of stope roof stability using in situ measurement data on modulus of deformation. From the studies into deformation processes in undermined rock mass, deformations of stoping system elements are related with the surface subsidence. For the stability control in permeable strata, the system of monitoring of rib pillars is developed. Measurements of deformations in host rocks surrounding stopes show that the most informative parameter is lateral deformation of pillars. In this connection, as a criterion of pillar stability, it is recommended to use the value of lateral deformation measured at some distance from the boundary of an underground excavation. A system of long-term measurement of lateral deformations using displacement sensors is proposed for monitoring stability of pillars. The integrated implementation of the experimental techniques and theoretical approaches allows increasing validity of stability prediction for structural elements of stoping system and for integrity of impermeable strata.

1. Available at: http://www.gosnadzor.ru/industrial/mining/acts/gornorud_object/pr599/ (accessed: 15.04.2018).
2. Sustainable development. Uralkali. 2018. Available at: http://www.uralkali.com/ru/sustainability/(accessed: 15.04.2018).
3. Usolsky Potash Plant – to future generations. Promyshlennost i bezopasnost. 2013. No. 5. pp. 52–55.
4. Territorial construction norms TSN 22-301-98. Building in the undermined territories of the Upper Kama Potash Deposits. Purposes of building protection activities. Perm : Perm Krai Authorities. 1998. 95 p.
5. Baryakh A. A., Lobanov S. Yu., Lomakin I. S. Analysis of time-to-time variation of load on interchamber pillars in mines of the Upper Kama Potash Salt Deposit. Journal of Mining Science. 2015. Vol. 51, No. 4. pp. 696–706.
6. Artkhonghan K., Sartkaew S., Thongprapha T., Fuenkajorn K. Effects of stress path on shear strength of a rock salt. International Journal of Rock Mechanics and Mining Sciences. 2018. Vol. 104. pp. 78–83.
7. Baryakh A. A., Sanfirov I. A., Fedoseev A. K., Babkin A. I., Tsayukov A. A. Seismic-geomechanical prediction of water-impervious strata state in potassium mines. Journal of Mining Science. 2017. Vol. 53, No. 6.
8. Sriapai T., Walsri C., Fuenkajorn K. True-triaxial compressive strength of Maha Sarakham salt. International Journal of Rock Mechanics and Mining Sciences. 2013. Vol. 61. pp. 256–265.
9. You M. True-triaxial strength criteria for rock. International Journal of Rock Mechanics and Mining Sciences. 2009. Vol. 46, Iss. 1. pp. 115–127.
10. Wang G., Zhang L., Zhang Y., Ding G. Experimental investigations of the creep–damage–rupture behaviour of rock salt. International Journal of Rock Mechanics and Mining Sciences. 2014. Vol. 66. pp. 181–187.
11. Stavrogin A. N., Tarasov B. G. Experimental physics and rock mechanics. Saint-Petersburg : Nauka, 2001. 343 p.
12. Baryakh A. A., Asanov V. A., Pankov I. L. Physical and mechanical properties of salt rocks at the Upper Kama Potash Salt Deposit : Educational aid. Perm : Izdatelstvo Permskogo gosudarstvennogo tekhnicheskogo universiteta, 2008. 199 p.
13. Zong Y., Han L., Wei J., Wen S. Mechanical and damage evolution properties of sandstone under triaxial compression. International Journal of Mining Science and Technology. 2016. Vol. 26, Iss. 4. pp. 601–607.
14. Li H. Z., Xia C. C., Wang X. D., Zhou J. F., Zhang C. S. Experimental study on deformation and strength properties of jointed marble specimens. Chinese Journal of Rock Mechanics and Engineering. 2008. Vol. 27, Iss. 10. pp. 2118–2123.
15. Liang W., Yang C., Zhao Y., Dusseault M. B., Liu J. Experimental investigation of mechanical properties of bedded salt rock. International Journal of Rock Mechanics and Mining Sciences. 2007. Vol. 44, Iss. 3. pp. 400–411.
16. Zhang H., Wang Z., Zheng Y., Duan P., Ding S. Study on tri-axial creep experiment and constitutive relation of different rock salt. Safety Science. 2012. Vol. 50, Iss. 4. pp. 801–805.
17. Pankov I. L., Asanov V. A., Udartcev A. A. The research on the influence of load degree and sample shape on salt rock deformation during creeping. Gornyi informatsionno-analiticheskiy byulleten. 2013. No. 1. pp. 246–252.
18. Dyagilev R. A., Shulakov D. Y., Verholantsev A. V., Glebov S. V. Seismic monitoring in potash mines: observation results and development aspects. Eurasian Mining. 2013. No. 2. pp. 24–28.
19. Asanov V. A., Baryakh A. A., Toksarov V. N., Evseev A. V. Geomechanical analysis procedure for long-term stability of rib pillars. Science and technology to support mining: International scientific and practical conference proceedings. Almaty. 2015. Vol. 87. pp. 91–95.