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

During the construction of a section of the S-7 Lubien - Rabka-Zdroj 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.

Automated summary

During the construction of the S-7 Lubien - Rabka-Zdroj dual expressway in South Poland, damage to the embankment and pavement was observed due to complex tectonic and geological conditions, including a shallow groundwater table and landslides. In order to stabilize the road, injections were carried out using the electrical resistivity tomography (ERT) method to identify the geological structure and evaluate the effectiveness of the injection process. ERT effectively delineated the fractures in the flysch and determined the penetration depth of the injection mixture and the degree of filling in the loosening zone.