Phase 2 - UXO detection

If the preliminary UXO research (phase 1) considers it necesary, the UXO detection (fase 2) will be carried out. The goal is to determine  the position (x, y and z coordinates) of the suspect unexploded ordnance (UXO) using geophysical techniques. We will advise the client about which (combination of ) techniques to use to achieve the best results. A solid and thorough UXO detection survey will prevent unnecessary expenses in the following phase.

Measuring techniques
During field activities parallel measuring lines are run across the investigation area, moving along the selected research equipment. In some cases, when the survey goes deeper than 4 meters,  T&A uses boreholes for measuring or incorporates research equipment in a probe. In this phase, the investigation area will not yet face intensive surface-disturbing activities.

Suspect objects
After the geophysical survey the location of metal objects, possibly UXO, in the subsurface is known. In some cases we can also give an indication of the dimensions of the objects. Other disturbing factors in te subsurface, like tubes, cables and layers of debris, will also result from the (combined) detection research. The results determine the further measures to be taken.

There are various techniques for mapping the subsurface or constructions. Based on our knowledge and practical experience we determine which technique will be most succesful for each investigation. Important factors to take into consideration are for example depth, specific circumstances, precision, measurement speed and costs.

Performing the measurements
Objects or geological transitions in the subsurface have a direct or indirect effect on the signals sent by the measuring equipment or the natural magnetic fields. Geophysical measuring equipment registers these effects. With the collected data a 3D image of the subsurface or construction can be created.

The measurements are performed by moving the equipment over the research location by foot or by car. Sometimes electrical wires are placed on the surface. Deep-seated, small objects or thin soil layers with similar characteristics are very difficult or sometimes impossible to detect from the surface. In these cases the equipment is brought closer to the objective, for example by using a borehole.

All applied geophysical techniques are non-destructive, making the location accessible immediately aftet the survey. Sometimes a location has to be partly fenced off or mobile fences are used.

Results
In most cases the results are not immediately available in the field. The collected data need to be analyzed in the office and a report is made. The results are presented, depending on the objective of the survey, in an index map, a cross direction profile or a contour chart of the subsurface.

UXO
The geophysical surveying techniques applied by T&A for the detection of explosives all respond to substance changes in the subsurface caused by metal objects. All of these detection techniques have been tested worldwide and have been found suitable for the detection of explosives.

Techniques used by T&A:

  • TISA 2D Borehole Radar
  • TISA 3D Borehole Radar 
  • 3D Radar
  • Borehole magnetometer (CPT) 
  • Borehole metaldetector 
  • EM-61 Metal Detector 
  • Ground Penetrating Radar 
  • Manual metal detector  
  • Magnetometer and Gradiometer 
  • Multisonde gradiometer 
  • NanoTEM 
  • Sidescan sonar 
  • Sub-Bottom Profiler