SIGI LLC, Prokopyevsk, Russia:
A. I. Bykadorov, Chief Executive Officer, Candidate of Engineering Sciences
D. N. Degtyarev, Deputy Head of Laboratory, degtyarev1708@yandex.ru

Resurs LLC, Novokuznetsk, Russia:
S. A. Smirnov, Technical Officer
O. Yu. Pechenegov, Deputy Technical Officer

One of the critical requirements imposed on subsoil users by the Russian Law on Subsoil is complete extraction of minerals. Coal mining in open pits in Kuzbass is associated with considerable loss of noncommercial reserves in pit wall rock mass between the technologically feasible and the license limits. Extraction of such reserves allows reduction of mineral loss, extension of coal field life and earning of extra profit. To the effect of the maximal extraction of mineral reserves after the open pit mining has reached the ultimate limits, the highwall mining systems (HMS) are widely applied in coal mining in Kuzbass. Despite more than 15 years of this method use, geomechanics of the undermined rock mass and ground surface is yet poorly studied. The main regulatory document on safety of buildings, structures, utility lines and natural objects subjected to harmful effect of coal mining, based on the longterm instrumental monitoring, laboratory tests and analytical studies of land movements, contains no calculation procedure of anticipated displacement and deformation of ground surface undermined by HMS. Based on the previous research and new results of the on-going instrumental observations over land displacements due to undermining by HMS, this article authors have found that rock falls in production rooms are directly preceded by sloughing and spalling of coal, as well as by sagging and slight doming of roofs. A rock fall occurs within a day and by the maximal value of subsidence. The maximal after-subsidence makes 12 % of the maximum subsidence. The regular patterns of subsidence and horizontal displacements are revealed, the empirical dependences are found, and guidelines on determining distribution functions of subsidences are presented. The angular parameters of the displacement zone are found, and the formulas of the expected maximum horizontal displacement and the sizes of the subsidence zone are given.

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