Tomisław Gołębiowski

Velocity analysis in the GPR method for loose-zones detection in the river embankments

Determination of continuous distribution of the loose zones in the river embankment between points of geotechnical investigations is a very important matter for the embankment stability during the flooding. Presently, only non-invasive, geophysical methods can deliver such information. On the basis of numerous tests carried out by the Department of Geophysics at AGH University of Science and Technology in Cracow, the following conclusion may be drawn: zero-offset, reflection GPR profiling very seldom gives positive results at the detection of the loose-zones in the levee. Therefore, another concept of the loose-zones detection, using the GPR method, is presented in this paper. This technique is based on the modified CMP profiling, which allows to prepare a velocity map. Such a map may be used for evaluating of degree of the embankment disintegration.

Aiding of the GPR method by other measurement techniques for liquid contamination detection

In the paper the selected results of measurements carried out for detection of two types of liquid contamination are presented. The authors made detection of contamination, which very often leaks to the ground, i.e. the low-conductivity hydrocarbon contamination and the high-conductivity chemical solution. Depending of the site and the type of contamination different measurement techniques were used: the GPR, the atmogeochemical measurement, the laboratory analysis, the resistivity imaging survey and the conductometry. A brief discussion about possibilities of liquid contamination detection using electrical and electromagnetic techniques is presented in the paper.

The use of GPR attributes to map a weak zone in a river dike

Dike leakage can be the result of a rupture and the formation of loose zones which are not able to stand the water pressure during flooding. Loose zones are significantly more saturated when it rains and floods than the undamaged portion of the dike. Due to the increased water in loose zones, their electrical properties are changed, particularly dielectric permittivity. As a result, these zones have a different ground-penetrating radar (GPR) wave reflection coefficient and are a source of wave diffraction. The interpretation of GPR measurements carried out on a leaking dike during a flood event in Poland is presented in this paper. The GPR attributes, such as an instantaneous phase, envelope, instantaneous frequency averaged over time and traces, have been analysed in the paper the interpretative tools. Also, the averaged spectrum (spectrum calculated from averaged traces) and moving spectrum (averaged spectrum calculated in windows moving along the traces), as well as the phase spectrum, of recorded GPR data were analysed as indicators of the existence of the deterioration of parts of the dike. As shown in the paper, the use of GPR signals attributes and spectra in the interpretation of field measurements can increase the available information about the structure of the dike by highlighting some of the physical properties of its construction.

Application of electrical and electromagnetic methods to study sedimentary covers in high mountain areas

The results of geophysical studies conducted with selected electrical and electromagnetic methods in the Kondratowa Valley in the Tatra Mountains (the Carpathian Mountains, Poland) are presented in the article. The surveys were performed with the following methods: electrical resistivity tomography (ERT), georadar (GPR) and conductivity meter (CM). The objective of the noninvasive geophysical measurements was to determine the thickness of the Quaternary postglacial sediments that fill the bottom of the valley and to designate the accumulation of boulders deposited on Quaternary sediments. The results of ERT surveys conducted along the axis of the valley allowed to determine the changeability of the thickness of the postglacial sediments and allowed to designate a few areas of occurrence of boulders. The ERT, GPR and CM surveys conducted across the valley allowed to designate with high accuracy the thickness of the accumulation of boulders sliding down the valley bottom from the couloirs surrounding the valley.