Stability of underground openings in salt rock masses

The study analyzes stresses and strains in rock mass enclosing single underground openings in sylvinite bed at a depth of 1100 m. The roof of the stopes is closely spaced with anhydrite and anhydrite–dolomite rocks, and the floor rocks include carnallite layers. The mathematical modeling was performed by the finite element method analysis of an elasto-visco-plastic model of rock mass in ANSYS. The source parameters of the models were obtained in the lab-scale testing of rock samples. The model was verified using the in-situ instrumental observations of deformation in underground openings. The numerical experiments are implemented for a single stope with an oval arched cross-section 6.0 m wide and 3.7 m high. It is found that stability of a single stope in salt rock mass is conditioned by its cross-section position relative to weak carnallite layer in the floor and strong anhydrite and anhydrite–dolomite layer in the roof. The relations for sizing the post-limiting deformation zones in enclosing rock mass are obtained. It is shown that there exists an optimal thickness of salt rocks to separate the stope roof from anhydrite and anhydrite–dolomite layers. The displacement analysis of exposed rock surface versus time reveals that close-spaced occurrence of anhydrite and anhydrite–dolomite rocks relative to the roof of a stope driven in rock salt changes the behavior of deformation of exposed rock surface. The obtained results are meant for the scientific support of underground mine planning and design.

Morozov I. A., Pankov I. L., Toksarov V. N. Stability of underground openings in salt rock masses. MIAB. Mining Inf. Anal. Bull. 2021;(9):36-47. [In Russ]. DOI: 10.25018/0236_1493_2021_9_0_36.

The study was supported by the Ministry of Science and Education of the Russian Federation within the framework of State Contract No. 075-03-2021-374 dated December 29, 2020, as well as by the Russian Foundation for Basic Research and the Perm Krai Government, Project No. 19-45-590004.

I.A. Morozov, Senior Lecturer, Perm National Research Polytechnic University, 614990, Perm, Russia, e-mail: imorozov.work@yandex.ru,
I.L. Pankov¹, Cand. Sci. (Eng.), Senior Researcher,
V.N. Toksarov¹, Cand. Sci. (Eng.), Senior Researcher,
¹ Mining Institute of Ural Branch, Russian Academy of Sciences, 614007, Perm, Russia.

I.A. Morozov, e-mail: imorozov.work@yandex.ru.

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