Geoelectrical Imaging for Site Investigation for Urban Underground Infrastructure

Unstable rock, groundwater inflow and other unforeseen ground conditions are risk factors that often lead to delays and large additional costs in connection with underground infrastructure construction work. In order to handle these risks first-rate knowledge of structural data, bedrock and soil geology, geotechnical conditions, nearby underground facilities, buried waste, contaminated ground and groundwater is needed.

Preliminary site investigation for underground construction is often exclusively based on drilling. Drilling provide detailed information in discrete points, but no information in between boreholes. Modern geophysical imaging techniques can map the subsurface space in 3D in a time-and cost-effective way. In particular, combined mapping by resistivity and time domain induced polarisation (DCIP) shows great potential for investigation in infrastructure applications, but the urban environment often presents challenges that require further methodological developments.

The project aims at adaptation of DCIP imaging for use in urban environments, through the development of: data acquisition methodology, DCIP prototype equipment, data processing, inversion techniques and relationships between geophysical and engineering/geotechnical/environmental parameters. Detailed project planning and strategy for handling risks in project implementation will ensure the success of the project and the effective dissemination of proposed outcomes.

Unstable rock, groundwater inflow and unforeseen ground conditions such as buried waste and contaminated ground are riskfactors that often lead to delays, environmental pollution spreading and large additional costs in connection with underground infrastructure construction work.

This project aims at adapting and improving geoelectrical imaging techniques for use in urban environments, through development of: data acquisition methodology, prototype data acquisition equipment, data processing, inversion techniques and relationships between geophysical and engineering/geotechnical/environmental parameters. The developed concept will be useful as a tool for making the underground transparent by creating 3D models of the subsurface and contributing to better site investigations. The increased amount of information obtained in the investigation decreases the uncertainties and risks in
the process of planning, construction and operation of underground infrastructures.

A greater knowledge of the site conditions will lead to better planning for construction projects and thus to minimise delays, unexpected costs and environmental pollution. This will contribute to create a good built environment and groundwater of good quality, a reduction of waste and a decreased need for virgin resources in the process. The proposed methodology optimises the use of resources in consecutive studies and contributes to cost- and resource effective planning and implementation.