Geoelectrical Imaging for Pre-investigation for Urban Underground Infrastructure

The project is part of the Geoinfra TRUST framework that is working towards developing techniques for more cost efficient and sustainable underground construction in urban areas (see http://trust-geoinfra.se/ for more information). This project aims at development and adaptation of DCIP (DC resistivity and induced polarisation) imaging for use in urban environments, and includes demonstration and evaluation of geoelectric map-ping in this context. Establishment of how well engineering and environmental key parameters can be estimated from models based on time-domain spectral IP is another aim. One part of the work is 3D data acquisition methodology and strategies, including different electrode arrays and combina-tions of surface and borehole electrode arrays. Adaptation and evaluation of data acquisition equipment is included, where evaluation comprises synthetic examples from numerical mod-elling as well as field experiments. Development of software for 3D inversion of spectral time-domain IP data is a key part of the project. Ways of integrating other types of data in the inversion process are also part of the task.The possibility to establish more accurate characterisation of engineering and environmental key properties based on models derived from inversion of spectral time-domain IP data will also be investigated. This includes soil and rock properties, tectonic structures, existence and character of buried waste and derelict industrial areas, as well as water and contaminant occurrence and transport. Preliminary evaluation suggests that free phase chlorinated hydrocarbons are visible as high resistive zones.