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Recognition of the flysch substrate using the electrical resistivity tomography (ERT) method to assess the effectiveness of the injection process

Ćwiklik Michał, Pasierb Bernadetta, Porzucek Slawomir

Geology, Geophysics and Environment

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2023

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Vol. 49, no. 2

197--202

EN

During the construction of a section of the S-7 Lubień – Rabka-Zdrój dual expressway, located in the area of the Carpathian flysch (Carpathian Flysch Belt, South Poland), damage to the embankment was observed, as well as cracks and depressions in the new pavement. An analysis of the geological and engineering conditions in the area of the road section under construction showed the existence of a complex tectonic structure of the flysch formations, a shallow groundwater table, and numerous landslides. In order to stabilize the road substrate, it was decided to carry out injections, and the locations of these injections were initially geotechnically tested. However, due to the high variability of the geological structure, the target method employed was electrical resistivity tomography (ERT), which performed the survey in two stages. In Stage I, the geoelectrical/geochemical structure of the near-surface zone was identified, and the probable causes of road damage were indicated. This stage was completed by performing the stabilization and sealing process of the ground with an injection mixture. In Stage II, studies were carried out to evaluate the effectiveness of the injection process. The ERT method effectively identified the shallow geological structure and, in particular, delineated the zone of strong fractures in the flysch and areas associated with faults. Using the electrical resistivity tomography method, it was also possible to determine the injection mixture’s approximate penetration depth and the loosening zone’s degree of filling.

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Depth estimation problems in microgravity survey

Porzucek Slawomir, Loj Monika

Acta Geophysica

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2021

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Vol. 69, no. 2

665--672

EN

Qualitative interpretation is one of the most important missions in geophysical methods, particularly the determination of the shape and depth of disturbing bodies. The characteristics of the gravity feld make it difcult to unequivocally determine both of these parameters; therefore, the problem is solved by reducing the shape of the body by means of simple solid fgures and on this basis an attempt to estimate their depth. This paper presents an analysis of depth estimation in microgravity surveys. The useful signal-to-error ratio in this survey causes an additional factor infuencing the quality of the estimated depths. Werner deconvolution and Extended Euler deconvolution, as the most frequently applied methods, were used to resolving the problem. Based on the Werner method, a processing methodology was developed that minimizes the impact of the error on the calculation results. An algorithm was also created that allows obtaining a depth solution in this method. The results of the Werner method were compared with the results of the Extended Euler method. Tests have shown that despite the relatively high error to amplitude ratio of the anomaly, satisfactory results can be obtained with the appropriate methodology.

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Detailed analysis of the gravitational effects caused by the buildings in microgravity survey

Loj Monika, Porzucek Slawomir

Acta Geophysica

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2019

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Vol. 67, no. 6

1799--1807

EN

Gravity (microgravity) research is more frequently carried out in urban areas, in close proximity to various types of buildings. It is necessary to take into account the gravity impact of these buildings on the measurements by calculating and factoring in the appropriate correction. The easiest method to calculate the corrections is to base them on simplified models of the buildings, approximated mostly by a rectangular prism. This paper presents an analysis of correction based on simplified models of six different buildings. It has been clearly demonstrated that density of a simplified model of a building or an element of the building is different from the average density, especially for gravity measurements inside the buildings. The research demonstrates that it is better to approximate the building with two or three rectangular prisms than with only one treated as a whole. However, the difficulty lies in determining the density of the lowest storey, the value of which diverges from the average density the most. Nevertheless, it can be concluded that in calculating building corrections simplified models of the buildings can be used, even for observation stations that are located in a close proximity to the buildings, as long as the conditions described in this article are met.