MODELS OF GEO-ELECTRICAL SOUNDING CHARACTERISTIC FOR COAL MINES (R. MACEDONIA)

Abstract

In this paper the geological structure of the modelled environment is shortly presented. The coal mine “Suvodol” is chosen for geo-electrical examination because it has been most thoroughly researched and has the densest network of mapped boreholes. Synthetic diagrams are made with the inverse method of geo-electrical sounding or with solving the direct task using the data from the mapped boreholes. The analysis of the mapped boreholes shows that the investigated area is mostly built from: - Gneiss – the main plate of the basin - Sands with different granularity - Composition of clay and sand -Sands with organic materials - Coal as a mineral resource The horizontally layered structure of the ore body in the investigated area allows favorable conditions for applying the method of geo-electrical sounding. During the construction of the models, special attention has to be dedicated to the level of underground water because of its dominant influence in the geo-electrical researches. The analysed boreholes are with depths up to 150 m, so while using the specific method the profiles of the sounds are modelled in length of 300 m (AB/2 = 150 m =>АB = 300 m). A total of 13 boreholes have been analysed in this paper and have been sorted into three parallel profile lines and two control crosscutting profile lines. The data about the specific electrical resistance of the materials in the investigated area that is generated from experiences gained while researching in similar areas is used in the process of modelling. The generated curves of geo-electrical sounding when resolved by the direct task can be in great value during the researches of this type of deposits. The improvement of the synthetic curves of the geo-electrical sounding requires more accurate data for the specific electrical resistance of the materials and that can be achieved with testing the materials in laboratory conditions that would be as close as possible to the actual. For acquiring the correct data for the specific electrical resistance of the materials it is necessary to perform field trials. Also the modelling would be more specific and more detailed if the influence of the level of the underground water is taken in consideration, but in the modelling in this paper that influence is not considered because of the synthetic construction of the diagrams and the lack of data from the field.