Borehole logging for detection of deeply buried UXOs

Aerial image of a bombed rail road

The challenge

The contamination of our grounds due to past and ongoing conflicts in the world is widely discussed. Especially in Germany, Austria, the Netherlands and the UK commercial companies (like the EOD Munitionsbergung from Austria) are contracted intensively upfront construction works. They clear the ground from not detonated bombs and ammunition. But there are areas where you can’t detect UXO from the surface. Those are sites with a very soft ground (so bombs are lying deep) or where the surface was compressed from leftovers of destroyed houses and infrastructure (so bombs are hidden under debris and scrap metal). Here, you need to invest into drill rigs and machinery. You need to drill a whole grid of boreholes (turning an area into a “Swiss cheese”) and insert plastic tubes to prevent drill holes from collapsing. After that you can start doing borehole logging with a magnetometer borehole probe – like the BM2 3axes system. The aim: detect deeply buried not yet detonated air drop bombs!

The solution for deeply buried UXO

Borehole measurement probes are specially developed to fit into slim boreholes and generate vertical measurements and data sets. These need to be processed and put into relation with all other vertical borehole data sets. The SENSYS borehole measurement products allow to survey vertical drill hole to a depth of 50 meters, angled and horizontal boreholes up to 160 meter and with the next generation of borehole logging system this will be extended to 1,000 meter to cross beneath rail roads, water ways or large metropolitan areas in front of infrastructure, subway, pipeline installation and others.

The most advanced SENSYS borehole logging system is the BM2 3Axis. It comes with two triaxial Fluxgate Magnetometers aligned in an aluminum sensor housing to enable various things:

  • recording x, y and z components separately of both sensors of an magnetic field or anomaly
  • enable not only vertical borehole measurements, but angled or even horizontal borehole measurements as well
  • 200 data sets per second allow a seemless plot of data and the best base for in-depth data processing
  • way information determined by an internal acceleration sensor is taken into account for length counting as well as for proper distribution of measurement data in regards to time/position.
  • interface to combine measurement data with GPS information to improve triangulation of data and calculate proper object parameters of the detected buried object
  • a wide measurement range of +/-250,000 nT to cope with infrastructure that allows to i.e. survey directly in front of bulk heads or other heavy magnetic noise sources

The biggest advantage of the SENSYS BM2 3Axis system is the mobility that comes with it. All parts are put on a ergonomic battery belt that hold battery, cabling and the recording unit. The operator only needs to have the borehole probe in his hand.

How does borehole data looks like?

The simulation below is showing an SD70 fragmentation bomb (as placed into the SENSYS GEOmil test field) at 2.5m depth. The middle sequence shows a set of vertical borehole measurements and how they visualize the magnetic anomaly of the SD70 fragmentation bomb. The very right picture overlays a surface survey (i.e. with the SBL10 or MXPDA)

The SENSYS software MAGNETO puts all data sets into correlation. Via a triangulation of three borehole data sets the object parameters (i.e. of the SD70 fragmentation bomb) can be calculated as well as the x,y and z coordinates of the object in the ground! At SENSYS we understand our role not only as a manufacturer, but as a companion as well. Thus, we are deeply involved into first project starts of clients with a newly purchased BM2 system. We offer in-depth training sessions, hands-on guidance in the field and data check. As the BM2 3Axis delivers several times more data compared to other logging systems, the opportunities are manifold as well to deliver the extra information you will need to decide if an detected object is a threat or not.

Supporting the internal DAkkS UXO workshop

In November 2020, we supported the field session of the advisors of the German institute DAkkS for accreditation of companies operating in the field of UXO search and clearance. The workshop took place at the training site of the Fire Department of city Hamburg. Their topic was a best practice of the state-of-the-art triaxial magnetometer borehole logging systems, which we supplied in form of presentation to physical principles but field test and trials as well.

A big thanks to EOD Munitionsbergung for their permission to use their photographs within that article!

Did you know: besides purchasing your own SENSYS equipment, you can also rent all kind of devices from us!

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