PII Radar Project

Predictive Modelling As A Tool To Improve The Effectiveness Of Sub-Surface Radar Investigations

Project Duration October 1999 to September 2000

Introduction

Subsurface radar is a powerful non-destructive investigative tool in many situations, being able to provide information about various types of construction or the shallow ground mass. It complements traditional investigative and sampling techniques. Radar is used in a wide range of construction applications including surveying roads, other types of pavements, reinforced concrete structures, tunnels and bridges. The project examines the feasibility of using predictive numerical modelling to assist the planning and interpretation of radar surveys.

Predictive modelling (PM) can be used both as a tool prior to a radar survey being undertaken to assess the likely success of the proposed survey or as a means of assisting with the interpretation of radar survey data already collected. This will not only improve the technical reliability of such surveys but will provide clients with better value for money and enhanced confidence in the results obtained. Currently this technique is not used extensively and an easy to use tool for this purpose is needed. PM is used to answer the question 'given this situation -what results are likely to be obtained ?'. In the case of subsurface radar it can improve:

The planning of surveys. Radar practitioners would be able use PM to guide their procedures on site, and hence improve the effectiveness of their work.
The interpretation of survey data. Radar results are complex and, although recent improvements in data collection procedures and processing have made interpretation easier, there is a pressing need for PM to make further improvements and to provide a facility to undertake various types of sensitivity analysis.
Client's understanding of the use of radar. Currently clients are completely dependent upon the practitioner to interpret the complex results of a radar survey. This interpretation is typically undertaken on the basis of past experience. This can pose certain difficulties and is not necessarily robust. There is a need to establish more scientific methodologies for interpretation that can be independently validated.

With the increasing use of novel construction designs and new uses being made of existing structures and sites, there is a need for improved non-destructive testing tools. These could give improved confidence that the new uses are appropriate and that the proposed designs have been implemented as intended. This feasibility study will enhance the use of subsurface radar for these purposes and enable its use to provide a greater insight into the condition of elements of the existing built environment.

The Project Partners

The Project Partners are:

Project Aims

The project is examining the use of predictive modelling within the sub surface radar business process. It is examining practical issues such as can the modelling be undertaken in the time available, can the models be used to plan surveys.

The Project Programme

The project has four stages, the first three stage examine the application of modelling to three survey situations to validate the method, the final stage critically evaluates the first three stages. The project has started the first stage which runs to the end of January 2000.

The Background to the Project

The project building upon the work undertaken by BRE and STS as part of the BRITE EURAM III project; Subsurface Radar As A Tool For Non-Destructive Testing And Assessment In The Construction And Building Industries; Project No: BE 95-2109. This project undertook extensive Finite Difference Time Domain Modelling of a wide range of structural situations.

The image below shows the output of a model where the radar pulse can be seen propagating through a reinforced concrete beam with an area of honeycombed concrete:

Propagating Radar Pulse Through Concrete(201kb)

Acknowledgements

The funding for this project was awarded under the Department for the Environment, Transport and the Regions, Partners in Innovation Schemme.

1999: STS Completes European Research Project

In conjunction with the BRE, Hochtief, BAM, Liverpool University, Politecnico Milano, ISMES and the Norwegion Geotechnical Institute, STS has completed a major research project to improve the understanding of the use of surface penetrating radar.

The research focused on three building materials; concrete, brickwork and blockwork. The project has enabled significant advances to be made in the analysis and interpretation of radar data collected, and in the presentation of results.

These examples illustrate a three-dimensional representation of part of a reinforced concrete slab produced from a high resolution survey. Also illustrated is the same data set showing the arrangement of transverse reinforcement bars.

Ground Penetrating Radar, GPR, SPR