УДК 550.837
https://doi.org/10.21440/2307-2091-2019-2-72-79
The results of the use of geophysical technologies for the study of hydraulic structures are considered.
The main purpose of the work was to determine the possibilities of noncontact methods of electromagnetic sounding during surveys of ground water dams. Soundings were carried out by induction installations with vertical magnetic dipoles and, in part, using electrical installations with capacitive parallel lines. VES surveys were used as a comparative reference method. The objectives of the research included identifying the main structural elements of dams and identifying anomalous zones by geoelectrical sections obtained by various methods of electromagnetic soundings. Quantitative processing of electrical data was carried out in the form of one- and two-dimensional (1D – 2D) inversions using software from different manufacturers. When testing algorithms for solving inverse problems, the method of two-dimensional inversion implemented in the RES2DINV program was found to be the best in terms of speed and quality of interpretation. With the help of this software, for the first time, the processing of remote induction soundings was performed with obtaining electrotomographic sections of ground water dams. The paper gives a comparative analysis of 1D and 2D inversion of electromagnetic soundings obtained at three ground water dams of the Sverdlovsk region. Comparison of the results of electrical and induction soundings showed good comparability of electrical properties, although in some cases there is a difference in the values of specific electrical resistances (CER) for direct and alternating currents due to the different nature of the conductivity of the objects under study. Processing the results with the use of 1D – 2D inversions allows us to determine the shape and structure of anomalous zones, areas of high water saturation and possible leak points according to specific electrical resistance. Studies have confirmed the high efficiency of electromagnetic methods in the inspection of hydraulic structures.
The relevance of the work is due to the increasing interest in the use of geophysical technologies for non-destructive testing of hydraulic structures. The purpose of the work: to find out the possibilities of using non-contact methods of electromagnetic sounding during surveys of ground water dams. Methodology of work: electromagnetic methods of geometrical soundings were used out by induction installations with vertical magnetic dipoles as well as using electrical installations with capacitive parallel lines. VES surveys were used as a comparative reference method. Quantitative processing of electrical data was carried out in the form of one- and two-dimensional (1D – 2D) inversions using software from different manufacturers.
Results. The research conducted at three ground water dams in the Sverdlovsk region showed that all the geoelectrical sections obtained on direct and alternating currents are similar in morphology. The main elements of the dams are clearly distinguished: embankment, base, spillway, as well as engineering structures (wells, etc.). One-dimensional (1D) and two-dimensional (2D) geoelectrical sections constructed using different sounding methods, turned out to be similar to each other, but with their characteristic features. In some cases, there is a difference in the values of specific electrical resistances for direct and alternating currents due to the different nature of the conductivity of the objects under study; however, the general features of the structural architecture of the dam are clearly visible on all sections. When testing algorithms for solving inverse problems, the method of two-dimensional inversion was found to be the most optimal in terms of speed and quality of interpretation. For the first time, remote induction soundings were processed to produce electro-tomographic sections of ground water dams with the help of that method. Conclusion. There is good comparability of geoelectrical sections for all methods of electromagnetic sounding. Processing the results with the use of 1D and 2D inversions allows determining the structure of dams by their specific electrical resistance, including the shape and structure of anomalous zones, areas of high water saturation and possible leak points. The conducted studies confirm the high efficiency of geophysical methods while the survey of hydraulic structures.
Keywords: ground water dam, electrical sounding, remote induction sounding, inversion, electrical resistivity, geoelectrical section, geotomography.
The authors express their gratitude to their colleagues from the Institute of Geophysics, UB RAS V. Yu. Gorshkov and A. V. Malikov for their participation in joint fi eld works.
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