Putiška R., Brixová B., Bednarik M., Tornyai R., Dostál I. & Budinský V., 2021: Shallow geophysical survey as a tool for compactness verification of the underground sealing wall. Acta Geologica Slovaca, 13, 2, 199–204.

Shallow geophysical survey as a tool for compactness verification of the underground sealing wall

René Putiška¹, Bibiana Brixová¹, Martin Bednarik¹, Rudolf Tornyai¹, Ivan Dostál² & Vladimír Budinský³

¹Department of Engineering Geology, Hydrogeology and Applied Geophysics, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, 842 15 Bratislava, Slovakia; rene.putiska@uniba.sk
²AEGEO Ltd., Karpatské námestie 10A, 831 06 Bratislava, Slovakia
³Institute of Geosciences, Faculty of Mining, Ecology, Process Control and Geotechnologies, Technical University of Košice, Letná 9, 040 01 Košice, Slovakia

Abstract

he aim of this paper is to assess the compactness of the underground sealing wall through selected geophysical methods as a part of the engineering geological research. Underground wall was realised by grouting concrete mixture through series of two parallel lines of grouting boreholes. The injected environment is represented by the Quaternary sediments, mainly by anthropogenic sediments and soils - weathered rock material of silt composition, clayey sand to clayey gravel with rock fragments up to 10 cm in size, and remains of concrete wall at a depth of 0.3–1 m. Under anthropogenic sediments, granite subsoil rocks were to be interposed by grouting boreholes. Electrical resistivity tomography (ERT), shallow seismic measurements (SRT), and georadar (GPR) were used to verify the compactness of the underground wall. Measurements were made on one profile of a total length of 94 m in the middle between individual grouting boreholes. The measurement results were confronted with geological documentation of boreholes. On one of the boreholes, an electrical resistivity measurement was made on the core sample, which showed that values up to 100 ohm.m represent an injection-free environment and the presence of the injection mixture is displayed by an increase in apparent electrical resistivity. The results of the ERT on the measured profile showed that the individual grouting boreholes behave discreetly, and neither in the vertical nor in the horizontal direction doesn’t form the pre-injected continuous homogeneous layer. Under the groundwater level, the injection mixture did not appear in the electrical resistivity tomography. The mixture was probably washed away in the groundwater flow. The building object was evaluated as non-compact in both horizontal and vertical directions. This result was confirmed also by borehole cores sampling and hydrodynamic testing in boreholes on the assessed section of the staunching wall.

Key words: geophysical methods, ERT, GPR, SRT, underground sealing wall, flood protection line, Danube River

Manuscript received: 2021-11-24

Revised version accepted: 2021-12-14