·Table of Contents
·Methods and Instrumentation
Search Means Based on the Methods of IntroscopyA.V. Kovalev, I. Yu. Pushkina (MSIA 'SPECTRUM', RUSSIA)
This menace denies the free access to the roadways and communication lines, threaten the life of civilians in villages and urban areas, set limits on the possibility of use of agricultural lands and other objects. All these obstacles to normal life stay active long after the end of war or after conflict is resolved.
The mines may be classified as follows:
Particularly dangerous are antipersonnel mines due to their large quantities and wide variety of types.
The mine fields are the source of increased hazard and stay hazardous for a long time after the mines were placed, and as a rule the primary victims of landmines are innocent, peaceful people.
In accordance with estimation given by the International Red Cross organization every month all over the world some 800 people die due to accidents with landmines, in most cases the injured persons are civilians. In total, since 1975, more than 1 million people died or were injured due to contact with landmines. The data from UN make it evident that landmines are the reason of death of about 10 thousands people and injury of some 20 thousands. Special anxiety is caused by the fact of non correlation between the rate of de-mining activity and the rate of mine planting, for example, instead of 100 thousands pieces of removed mines about 2 - 5 million of new ones are placed. It means that in case of such de-mining rate the number of non-removed mines to the end of the century, in accordance with different estimations, will increase from 90 -110 million pieces (the demining procedure for this quantity will cost about 33 billions dollars) to 120 - 150 millions.
The difficulties in connection with the problem of mine contamination and tendencies to the problem further complication is described by the leaders of the UN as follows:
"From all the types of the consequences following the end of any conflict mostly wide spread and harmful are land mines. They create the most dangerous and long active contamination of the lands ever met before. At present, we lose out in fight to protect peaceful civilians from injuries caused by mines".
In accordance with the requirements issued by the UN the demining operations must guarantee the probability of mines detection at the level of 99%, including the smallest anti-personal land mines hidden in grass or soil at the depth of 100 - 200 mm.
It is not difficult to assume that one of the most informative means, that provide development of efficient methods and design of high sensitive equipment, are the methods of introscopy, giving the reliable registration of informative parameters of the searched object (in our case this object is mines) over the noise background generated by screening media.
In the list of screening media the next can be included:
The basic disclosing parameters of mines and explosive devices (ED) are listed in table 1.
|The name of the contrast existing between the object and holding media||The type of searched object|
|APsL||ATM||Mines and ED with electronic components||ED with wire control line|
|Contrast in electric conductivity||+||+||+||+|
|Contrast in magnetic permeability||±||±||+||+|
|Contrast in dielectric permeability||+||+||+||+|
|Contrast in thermal properties||±||±||±||±|
|Contrast in optical parameters||±||±||±||±|
|Contrast in mechanical parameters||+||+||+||+|
|Presence of explosives vapors||±||±||±||±|
|Presence of non-linear electromagnetic parameters||±||±||+||±|
|Table 1: Disclosing parameters of mines and explosive devices|
In the figure 1 the chart of basic methods for mines and ED detection is presented. This chart may be used like basis for development of technical means for registration of searched objects' disclosing parameters.
|Fig 1: Basic methods of mines and ED detection.|
Nowadays, in Russian developments the following methods are mostly often used.
Electromagnetic method is the basic one and successfully is implemented in various technical search and detection means. The presence of metal even in modern, so called, "non-metallic" mines containing only 0,1 g of metal, provides realization and makes the application of inductive method to be very promising. The best modern metal detectors has a sensitivity enough to detect 0,1 - 0,15 g of metal in the soil at the depth of 50 - 70 mm. The ways of the inductive method improvement are in their selectivity enhancing and in implementation of operating modes for finding of the space coordinates of searched objects.
Magnitometric method provides detection of metal objects of 'large' mass (artillery projectiles, large mines, air bombs, etc.) planted in soil and in water at the great depth (up to 3-5 m). The efficiency of its application for the goals of APsL detection is in doubt.
Radio wave method and instruments based on this method (Russian instrument RMB-2 or American instrument AN/PRS-8) provide detection of practically all types of mines and ED as well as any dielectric anomalies and hollows in soils at depth of 150 - 200 mm. Nevertheless, the main disadvantage of this method is big number of false pick ups or alarms. The last ones reduce the detection rate limiting it to the approximately 80 - 100 sq. m per hour, require additional verification of obtained results with the help of equipment based on the other principles of operation including prove by mechanical search.
Non-linear method based on the registration of harmonics in the spectrum of reflected UHF signal. This method is rather efficient in case of remote search for mines and ED with built-in electronic components (electronic detonators, seismic, Infra Red and acoustic timers, etc.). At the same time, the mines with conventional detonators can not be detected by means of non-linear radio locating systems (NLRLS).
The possibility to create the technical means based on nuclear-physical method was proved more than two decades ago. The main idea of the method is the registration of secondary radiation generated as a result of interaction of neutrons (for example, of Cf-252 isotope or portable generator) with the explosive atom' nucleus. The use of such technical means is limited due to the issues connected with the operator's safety and low search rate.
Thermal method of inspection at present is classified by increasing number of specialists like most informative and capable to provide simultaneously the high sensitivity, the reliability and reasonable rate of search operations. But implementation of this method impose the requirement to develop new and improve existing search procedures as well as working out of information processing algorithms providing elimination of influence of high level interference caused by upper soil stratum' heterogeneity and by flora.
Mechanical search method since the first time of APsL use and up to now is the method of verification of results obtained with the instruments based on the other methods. Lately the searching tracers (l » 1-1/5 m and Æ » 8 - 12 mm) are fabricated from nonconducting materials, due to this is reduced the probability of de-miners blow ups that may be caused by the contact of the tracer and the trap-mine' electrical contacting fuse. The method is characterised by low search rate and the subjectivity of the obtained results.
Every mentioned in the paper method has its advantages and disadvantages, nevertheless, their integration in one searching system will increase the search rate, reliability of the results and safety of demining operations. The first obtained in this filed results proved the estimations done in advance. The main goal facing specialists working in this field is to find the optimal combination of inspection methods that would provide the most efficient proportion in the chain "search rate - reliability - price".
The problem of territories demining unfortunately is spreading over the countries and the attempts to solve this problem and to help people to live in peace became more and more persistent. In Russia, up to now, we are meeting mines and air bombs left from the second world war in the land. Russian scientists know the problem not only from books or articles, that is why they started to develop the instruments for dangerous object search and demining long ago and gained reach experience in the field. Nowadays, due to the new good tradition to joint efforts to solve the problems common to many countries and touching citizens not only of your own, native country, but of other countries as well, the Russian specialists are participating in the working group: 'Antipersonnel Landmines Detection' under the leadership of the European Federation for NDT and will contribute there best in the technological advance and progress in humanitarian demining.
|© AIPnD , created by NDT.net|||Home| |Top||