Monitoring of geological environment during mining using land and in-mine seismic surveys

This research aims to assess feasibility of control over geological environment in the course of mining operations with the help of land and in-mine seismic and detection of possible changes in hypsometry of geological boundaries and in physical and mechanical properties of rocks in time (monitoring). The subject of research is the salt strata and overlying rocks at the Verkhnekamskoye Potash Deposit situated in the area of the Berezniki and Solikamsk towns in the Perm Krai. The line of the land seismic survey coincides in plan view with one of the underground seismic lines. The land seismic study involved excitation of spherical waves by blasting explosive charges embedded in blastholes and the reflected wave method of the common depth point (RWM CDP). In the in-mine seismic study and monitoring at the inner points of the test environment, the point force was excited by an impact directional source with recording of shear waves using RWM CDP with separation of reflections (SWSR). As known, stopping operations induce subsidence of ground surface which may cause changes in properties of rock mass above stopes. Within the research framework, the data of land and in-mine seismic are correlated with each other and with the acoustic logging (AL) and underground testing results. The results prove a good agreement between the recorded data on locations of the main reflecting boundaries and on temporal thicknesses of the main lithologic types. Within the research, the major advantages and limitations of the discussed geophysical methods are determined. Land seismic is convenient to study geological structure and detecting large changes connected with strong subsidence and deformation, and is suitable for monitoring critical sites of the geological environment, with a complex geological and tectonic situation, after mine closure—with a view to controlling solution of salt strata. In-mine seismic allows highly detailed monitoring sensitive to even minor changes in the geological environment.