Complex Electromagnetic Monitoring of Salt Mines
Kolesnikov, Vladimir Petrovich; Laskina, Tatiana Andreevna
Perm State University, Russian Federation
Distortion of the waterproof strata within salt mines is extremely hazardous due to very high solubility of salt rocks. Often it leads to catastrophic mine flooding, salt karst and following subsidence and sinkholes in different regions of the world (Russia, Germany, USA, Canada, Belorussia and others). Geological, geophysical, hydrogeological and other methods are applied to investigate these processes. However, the accuracy of prediction is not enough for timely detection of potentially dangerous zones and taking measures. So development of geophysical methods to control and predict these dangerous geological processes is very important.
Electromagnetic methods are characterized by a number of informative capabilities, which are quite important for salt deposits. Electrical resistivity depends on such general physical properties as density and water content of rocks, additionally it is sensitive to changes of water mineralization and gas content, which are also associated with the salt karst process development. Practical implementation of the electromagnetic surveys opportunities is connected with the development of technologies in appropriation with geoelecrical and anthropogenic conditions of salt deposits and peculiarities of investigated processes. To increase accuracy, informativeness and effectiveness of prediction we use the complex electromagnetic technology on the base of the integral multi-frequency sounding in surface and surface-mine modifications, group sounding method and stationary monitoring systems.
An analysis of the experimental electromagnetic monitoring surveys results allowed us to determine a number of typical predictive criteria and peculiarities of the manifestation of salt karst processes in electromagnetic fields, including the expressed dynamics of water mineralization change in the productive salt strata interval, the gas-dynamic and subsurface subsidence-collapse cyclicities. They show typical features of gas accumulation and outburst owing to the distortion of salt rocks, the identification of gas migration pathways in the overlying sediments, the subvertical zones of the fractured rocks with the subsurface collapses, and others. The determined peculiarities significantly influence the stages of the sinkhole formation development. The dynamic geoelectrical model of sinkhole formation has been designed for the predictive assessment of negative processes development under the conditions of salt mines.
The monitoring technology provides an opportunity to increase accuracy of negative geological processes prediction and safety of mining and other human activity on a salt deposit territory. The results of research also can be used for monitoring of physical condition of different geological and technical objects (tunnels, hydroengineering constructions and others) as well as to solve a number of other problems.