Research Institute of Mining Geomechanics and Mine Surveying — Intersectoral Scientific Center «VNIMI»(Saint Petersburg, Russia):

Ermakov I. I., Senior Researcher, Candidate of Engineering Sciences, e-mail: labust@mail.ru
Pustovoytova T. K., Head of Laboratory, Candidate of Engineering Sciences
Ermakov O. I., Junior Researcher

«Geostroyproekt» LLC (Saint Petersburg, Russia)

Gurin A. N., Investigation Director

This article proposes an estimation on the stability of pit edges, with the solution, on terms of limit equilibrium of restraining and shear forces in general statement of problem. This estimation is based on detail research of the following factors:
-structural and tectonic composition of rock massif;
-physical and mechanical properties of burdens and deads, including the full-scale tests;
-hydrogeological conditions of Lomonosov diamond deposit.
Development of the deposit has complex hydrogeological conditions. This is explained by the presence of six water-bearing complexes in the cut mine, as well as by their power nature, and by the development of salt waters on the depths of 215-220 m.
Deads of the deposit have subhorizontal occurrence. Meanwhile, subhorizontal thin argillite interbeds with poor mechanical properties are spread across the whole width of these deads. These argillite interbeds are, practically, the natural surfaces of weakening.
The planned shape of the considered open pit is close to the circle (orthogonal diameters comprise 1110,4 m and 1000,9 m). In this case, stability of edges is higher than stability of the planned rectilinear open pits, at the expense of additional resistance to displacement of the possible sliding wedge, which is created by the forces of horizontal stress. The degree of influence of the forces of horizontal stress depends on the planned edge configuration, geological structure of near-edge massif, and ratio of length of edge and its height. Taking into account the foregoing, there were made the calculations of stability of slopes and estimation of maximal parameters of edges of the considered open pit with its project depth of 340 m.
The obtained results make it possible to do the comprehensive introduction of necessary activities for efficient exploitation of the deposit to the project depth with maximally possible parameters of the stable edges of the open pit of Arkhangelskaya pipe.

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