A series of comparative trials of manual demining tools and procedures were undertaken at Moamba in Southern Mozambique, with essential assistance from (UN) ADP which was the national dmeining programme at the time. These limited trials pitted varied manual demining techniques against each other in a common controlled environment in order to assess their relative efficiency in terms of speed and safety. Various demining groups were invited to participate, and NPA in Mozambique, NPA in Sri Lanka and ADP Mozambique provided essential manpower, training and monitoring assistance.
To maximise the quantitative output that would be of statistical value, the German institute BAM advised during the planning phase. To maximise the objectivity of the analysis of the results, the British research group QinetiQ, BAM, GICHD and ADP QA staff assisted with the monitoring of the trials. All, including the deminers themselves, produced analyses of what could be derived from the trials. Some of the results are qualitative, and some quantitative. When all results coincide, there is reason to have an unusually high level of confidence in the accuracy of that result.
Eight manual demining techniques were compared in terms of speed, safety to the deminer, safety to the end-user, comfort and confidence. These methods were:
- standard metal-detector use with signal-investigation tools;
- standard metal-detector use with magnet attached to signal-investigation tools;
- standard metal-detector use with signal-investigation tools and a “magnet Brush-rake”;
- area-excavation using an enxada (mattock) and conventional investigation tools;
- area-excavation using a conventional garden spade and conventional investigation tools;
- area-excavation using an NPA excavator and conventional investigation tools;
- area-excavation using a rake-based system (REDS); and
- prodding, using standard low-friction prodder and conventional investigation tools.
The standard use of metal-detector with magnetic signal-investigation tools was repeated with and without excessive fragmentation in the area, and a separate trial (designed by BAM) to determine the accuracy of deminer pinpointing was also conducted.
The trial area was set up with identical test lanes from which all undergrowth had been removed. The lanes contained concealed mine surrogates that accurately reflected the size and detector signature (to the Minelab F1A4 that was used) of Type 72 AP blast and GYATA-64 AP blast mines. Randomly placed in a manner that ensured that the deminers did not know how many were in an area, the surrogate mines included a witness plate on the top surface to record damage that occurred during their recovery.
The trials compared entire systems, not just the tool variations. The systems included area-marking and internal QA from the supervisors of the deminers. For all systems, the required search and clearance depth was the Mozambique National standard of 13cm.
All systems except prodding were effective at locating mines, although some deeply buried mines were missed in some systems. In most cases, those missed were Type 72 surrogates buried at 12cm to the top of the mine (about 13cm to the top of the metal insert).
In a heavily fragmented area, the most efficient method of clearance was using a metal-detector and a magnet Brush-rake. The use of signal-investigation tools that included a magnetic attachment was the next fastest. The use of a magnet Brush-rake in areas with cut vegetation or leaf litter might have given an even greater speed advantage.
When a metal-detector was NOT used, the most efficient method of clearance was that involving the use of a conventional garden spade and conventional investigation tools.
The method most likely to involve an accident to the deminer carrying it out was prodding. Prodding at 30° to the ground achieved an average search and clearance depth of less that 4cm, and all the mine-surrogates that were located during the trial had been damaged by prodding onto their pressure-plates.
After prodding, the method most likely to involve a deminer accident was area-excavation using a mattock (enxada), This finding coincides with that derived from the available accident records in the Database of Demining Accidents (DDAS).
The methods most likely to leave mines behind were prodding followed by area-excavation in which the required clearance depth was not maintained, and excessive speed meaning that deep signals were missed during metal-detector based search and clearance.
A post-trial evaluation of the methods and approaches employed during the trials determined that the variations between different demining teams meant that the different tools and methods were not the only variables affecting the results. Although the main team of ADP deminers had very similar skills and commitment, an expanded repetition of the trials that allowed each separate demining team (deminers and supervisor) to use each method in turn would provide a comparison that allowed individual human variations to be 'removed' from the results, so yielding more quantitatively compelling results. I would not expect the variations in the results to be significant but such a trial would show greater scientific rigour in its conduct.
