Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

Development of methodological design to define the specifications of the proposed geophysical acquisition and processing system for combined techniques

The state-of-art of the application of geophysics for contaminated sites characterization was complete. The first conclusion of this state-of-the-art is that research on geophysics for site investigation is still "under construction". The scientific community is just starting to understand the reality of contaminant-soil interaction and how each geophysical parameter changes with contaminant type, the time it is present in the soil and pore water chemistry. Nevertheless, it is possible to propose a survey methodology. Information related to the site description, the methodology used, etc. was extracted from a representative list of documents and subsequently analysed. The relation between site typologies and geophysical methods was also studied to know more about the applicability of the techniques.

First recommendation: a combination of 2 complementary techniques must be applied. Two combinations are useful:
- a slow and high resolution technique applied on anomalies detected by a fast but low resolution technique (e.g. electrical tomography with Slingram electromagnetics);
- 2 techniques measuring 2 different and not correlated parameters (e.g. seismics and electrical methods).

A second general recommendation is that a good site assessment must be carried out by environmental engineers and End users. The site assessment will help geophysicist to decide which technique is the more efficient in this particular context. Thus the Decision Support System (DSS) is a fundamental tool to help this assessment. DSS should focus on a particular problem: the geochemical and physico-chemical environment around the pollutants.

It is important to note that for site investigation 5 major problems can be distinguished:
- Geological setting
- Hydrogeological setting,
- Detection of abandoned or working buried utilities or objects (pipes, tanks, …),
- Direct detection of dissolved contaminants
- Extension of landfill

For each problem a number of most promising geophysical methods is proposed, however the selection of the optimal geophysical technique(s) is strongly site and problem dependent.

It is proposed to develop new equipment or optimise existing instrumentation that:
- has a high resolution and is not sensitive for conductive terrain
- works well on hard ground covers (asphalt, concrete)
- can look through reinforced concrete
- on the one hand are not too sensitive for ground heterogeneities or on the other hand can map the ground hetreogeneities
- work well under conditions where physical industrial sources are present (electrical currents, magnetic fields, ground vibrations)
- are certified to function in explosive environments.

Not all of these conditions are always valid at the same time, but these should be considered as normal industrial conditions. After analysis of the state of the art, the end-user's requirements and in view of the above mentioned problems the HYGEIA Consortium proposes several developments of geophysical methods to overcome the gap between the required specifications and the current possibilities in an effective way.

The proposed hardware developments are:
- development of a high resolution positioning system that is designed to be used for GPR measurements, for use on industrial sites where GPS can not be applied
- development of a portable seismic source for the generation of both P and S waves with sufficient energy that can be used on noisy and difficult accessible industrial sites,
- adaptation of the technology of «gimbal geophones» for continuous SASW field measurements on sites with a hard cover,
- development of a broad spectrum low frequency radar antenna that is aimed at increasing the penetration of radar waves (especially in conductive and heterogeneous terrains),
- adaptation of capacitative electrode techniques for measurement on terrains with a hard cover on industrial sites,
- development of impolarisable electrodes for measuring induced and spontaneous polarisation on terrains with a hard cover.

The proposed software developments are:
- development of GPR data processing algorithms that enhance the signal-to-noise ratio, e.g. coherent noise and reverberation removal
- GPR attribute analysis for potential direct detection of polluting materials
- development of an algorithm for migration of radar data : 3D migration for a detailed reconnaissance of buried utilities and 2D migration with a dip controlled operator
- development of a user friendly interface for the processing and interpretation of SASW data
- development of a user friendly interface for the processing and interpretation of self-potential data
- the development of more cost-effective bore hole to bore hole geophysical techniques on industrial sites where surface techniques can not be applied.

Información relacionada

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