Improvement of the techniques of mine clearance and subjects of studies
The Association of Research for Innovative Techniques in humanitarian Mine clearance proposes a series of scientific and technical studies to make progress the efficiency of the humanitarian mine clearance. In each of four domains in which of the progress are desirable, the problems are encircled, ideas are proposed as well as subjects of studies at the end of the chapter.
Clearing, cleaning of the vegetation
Before taking into account buried landmines, it is necessary to get rid of the vegetation and the surface landmines. The traditional solution is to conceive heavy heads of mowing, resisting to the explosion of landmines but provoking this latter. One can intend to endow the heads of mowing with a system of location of the tripwires and surface landmines, close to the mowing zone .These tripwires are generally metallic (the tripwire supplied with landmines is a steel wire coated by plastic); their length is generally of a dozen metres. They are arranged in a horizontal plane. One can think that they present particular characteristics of electromagnetic reflection. An action is going to begin to study this problem. If you want to participate, if you have ideas, contact John CRAWFORD.
One can wonder if systematic chemical weed-killers, which attack the green vegetables but do not pollute the ground, can be used, and in which conditions one can cope with their delay of action.
The fire is sometimes used to destroy the vegetation; it acts globally and in a not selective way (it destroys trees, which it is necessary to try to protect). It would be possible to concentrate the action of the heat near the surface of the ground, on the base of plants (thermal mowing, by laser beam)
Studies concerning the location at distance of the visible landmines(often metallic) and tripwires would be interesting to be performed. These landmines contain from some hundreds grams up to some kilos of steel; they are situated, either at 20 to 40 cm above the ground (landmines- pickets), or are slightly buried (bounding landmines), or sometimes they are fixed to a tree (directional fragmentation mines)
Propositions of studies
1. Light and resistant mowing head (not metallic?)
2. Location of the tripwires by their electromagnetic signature
3. Location of the tripwires by recognition of shape
4. Location of the fragmentation landmines
5. Clearing vegetation by chemical weeding
6. Clearing vegetation by combustion near the ground
7. Clearing vegetation by laser
The active detection
Several techniques depend strictly on the environment (ground, period of sunshine, humidity). In the case of the detection by infrared, attempts have been made to avoid the unpredictable character of the sun heating by replacing it by a source of heat: generators of warm air, combustion of napalm, microwaves, laser. These types of heater present all drawbacks: high cost, heat is limited to the ground surface, low yield of heat coupled into the soil, difficult control of the heat input. A more promising idea was emitted recently and : use the water as heat reservoir. It consists in spraying the ground with water loaded with a marker, or tracer (heat for instance, but also other markers) and observing the evolution of the concentration of this marker at the surface (or near the surface). The zones where the penetration of the water is delayed by the presence of a solid obstacle present a higher concentration of the marker.
The marker can be heat (warm water); the water gives up a part of the heat to the soil and the aqueous stream and the heat flow penetrate inside the soil. The mine presents a "thermal resistance ", because of the weak thermal conductivity of the organic constituents (plastic, explosive); on the other hand, the obstacle constituted by the mine disturbs the distribution of the water and of the heat around the mine; therefore, the surface temperature in this place is higher than in the surrounding ground.
Four possibilities of tracers are evoked below
|
Tracer |
Discovered parameter |
|
Heat |
Temperature of surface |
|
ions |
Electric specific conductivity of surface |
|
Magnetic particles |
magnetism of surface |
|
Chemical tracers |
Tracer surface concentration |
table 1: combinations tracer - discovered parameter
The principle of this type of active detection has been reported in several papers, in particular by the ISL. The interest of the active detection lies in the possibility of adjusting the parameters of detection (quantity of water, type and concentration of the marker, duration of the watering) to the environment: nature of the ground, temperature, hygrometry... and to use simple methods of detection. For example, the differences of temperature of surface over an obstacle obtained with an watering of warm water are of some degrees and can be detected by very simple sensors such as the infrared detectors with reduced sensibility (pyroelectrics, bolometres), as well as contact sensors of temperature (thermocouples, thermistors or even liquid crystals). It can be noticed that this technique allows a certain discrimination between landmines and stones: these last ones conduct well the heat as compared to the plastic landmines, which are insulating; the difference of temperature in the surface will decrease more quickly when the abnormality is a stone than if it is a landmine. The development of this method requires an important volume of studies, especially if a good understanding of the phenomena (modelling of the penetration of a fluid in soil in the presence of an obstacle) and a good control of the parameters are requested. However the techniques of measure neither are very sophisticated nor very specialised and the studies can be split in subjects to be handled by students.
Propositions of studies
1. Simulation of the liquid flow (water + marker poured on the surface) around a solid obstacle (landmine)) buried in soil
2. Device allowing to deposit uniformly a given water flow and water quantity onto a surface
3. Visualisation of the concentration of a marker on a surface (map of temperature, map of concentration of a chemical species, map of electric resistivity)
4. Measure of the concentration of a marker (resistivity, concentration of a chemical species)
Improvement of probes
The manual prodding consists in pushing a probe into the soil at an angle of 30 degrees. The prod is generally a metal point (sometimes amagnetic) 30 cm long. The prodding takes place every 3 - 5 cm. We were told that a trained deminer can determine the nature of the object which is hit by the probe.
Improvements are possible, consisting in improving the safety, the precision of the location, the penetration and the equipment of prods with detectors allowing to make simultaneously the detection and the elimination of the false alarms.
The location of the prodding can be realised by a leaky patch of sheaths facilitating the spacing of the prods. This device can obviously include one probe per sheath and the operator can then push the probe at distance by means of a jack, what allows an operation at the same moment faster and more secure (but does the identification function disappear?). The penetration of the probe in the ground can be improved by lubrication (hollow probe injecting some water) or by rotation of the probe, which can have a worm shape.
One can think of chaining the operations of detection and identification by equipping probes with detectors. When the probe hits an obstacle, it is a question of determining a characteristic property of this one allowing its classification..
Analysis by vibrations
Optical analysis: colorimetry, spectrometry
Measure of the thermal diffusivity
Propositions of studies
Improve the location, take away the operator, accelerate the operation. Take into account the fact that the manual mine clearance takes place in two phases: the first allows to track down a zone in which is a metal object; the manual prodding allows then to localise and to identify the metal object (landmine or false alarm). The zone has around thirty cm in diameter. Do not forget that the applied force should be controlled (less than 3-4 kg, dependent on which landmines are present in the minefield)
1. Sensibility of the deminer in the nature of the obstacle touched by the probe
2. Set of probes ("fork", matrix) with controlled force of penetration (and successive penetration of each probe)
3. Transmission at distance of the force (manual worker) of penetration of the probe (mechanical, pneumatic device)
4. Identification of an obstacle which is hit by the probe: use of characteristic properties of plastics compared with these of mineral or vegetal materials
* Hardness (penetration of a gimlet in the obstacle) - do not apply a too large force-
* Thermal specific conductivity (effect of a heating localised on the material)
* Analysis of vibration
* Optical analysis
5. Application of a localised heat flow (laser) and study of the reaction of the material (mechanical behaviour, decomposition, fusion...)
Neutralisation
The phase of neutralisation follows the identification, generally obtained by discovering the landmine, that is by removing the soil which covers it. According to the type of the landmine (and the skill of the deminers), one proceeds either to the neutralisation of the fire device for instance in putting in place the safety pin and removing of the detonator, or to the destruction of the mine (explosion of a high explosive charge).
In case the identification (or at least the classification of the object in possibility of landmine) is made without digging up the mine, it would be interesting to neutralise this one directly in the ground. One can proceed of several manners:
Studies were already published for the destruction of landmines or ammunitions at distance by intense heat (jet of hollow charge, very warm gas generated by combustion of fuel of rocket, laser beam) on landmines or UXO. The combustion of hydrocarbons is ineffective. It would be interesting to be able to provoke the combustion or the explosion of the explosive without moving the mine and removing the soil which covers the landmine. One has interest to avoid the explosion of the mine: the operation (at present usually made) requires to take many precautions, upsets the environment (disturbs clearance of surrounding landmines), some metal spreads of the explosion (especially for fragmentation landmines), what disturbs a lot the later use of dogs and metal detectors.
Action of the stream of intense heat on the common(current) materials of envelope of appearance(mine)
The water-jet is usually used for the neutralisation of bombs and explosive devices (destruction of suspect luggage in airports). Attempts showed that it does not agree to dissociate and neutralise landmines. On the other hand, the high pressure water-jet can be used for clearing the soil. One can also think of a high-pressure air jet
A foam, a cement injected by probe near the buried mine forms block with this latter and blocks the fuze, what allows to remove the mine mechanically without precautions. Such attempts were made to neutralise and remove a apparent mine.
Artificial nose : search for traces of explosives
Another interesting type of studies is the direct search for the explosive, by chemical means in particular. It is a question, following the example of the canine smell, of being able to track down the traces of explosive and\or constituents of the explosive (plasticizer, solvent...) which are present in minute quantities near the ground. These concentrations are very small. This type of analysis should allow to identify the presence of a mine (after detection of an abnormality). The analysis can last a certain time (one minute for example). It can be preceded by a stage of concentration of traces.
This study subject is very specialised and important laboratories deal with it. Except possessing important labs or having a really original idea, to deal with this subject will be difficult (within the framework of ARTID). The only study which may be interesting would be to make a modelling of the phenomenon of distribution of the explosive vapour in order to carry out a numeric simulation