Identification of geological faults by geophysical methods for risk assessment in underground mining

Abstract

High-accuracy prediction of geological faults, especially small-amplitude tectonic faults, is essential for an efficient and safe underground mining. Having such information about the location of tectonic faults in the rock mass reduces the likelihood of rock collapse and outburst, gas explosion, and water breakthrough during the mining operations. Modeling of the tectonic structure of the rock mass based on the data from the exploratory drilling and ground geophysical observations is of crucial importance to the extraction of mineral raw materials. Typically, in the areas of mineral extraction, tectonic faults in the rock mass are well studied using these data, but the predicted faults are represented by simplified imaginary surfaces that separate different structural parts of the rock mass and are not normally found by mining in such a form. The actual structure of tectonic faults is revealed in the course of mining, but the use of seismic survey is required for further prediction of such faults. The experience of applying these methods is shown in the examples of studies of tectonic faults of coal seams in the Donbass mines during the period from 2008 to 2012. To illustrate the capabilities of underground and surface 2D seismic surveys to accurately predict the location of faults, a site was chosen at the Dneprovskaya mine, which is characterized by the most amount of data collected from exploration drilling and geophysical methods. Also, in contrast to the mining practice when the coal seams areas are discarded based on the results of research due to difficult geological conditions or are not documented by geologists in the process of panel mining, this specific area is distinguished by the completeness of mapping of real faults exposed by mining operations. Predictions of faults obtained by preliminary and CDP seismic surveys are compared with the real faults exposed by mining operations. An example of research at the Krasnolimanskaya mine shown in this paper is among a few isolated cases utilizing 3D CDP seismic survey at mines. The results of the prediction of tectonic faults and the specifics of data processing and interpretation are examined. The research results considered in this paper can be used for further development of seismic survey methods for high-accuracy prediction of geological faults.