field testing of the sdtt segmented rollerfield testing of the sdtt segmented roller. drdc suffield...

Field Testing of the SDTT Segmented Roller

G.G. Coley Defence R&D Canada – Suffield

Defence R&D Canada – Suffield Technical Report DRDC Suffield TR 2003-107 October 2003

DRDC Suffield TR 2003-107 i

Abstract

In March and April 2003, the Canadian Centre for Mine Action Technologies (CCMAT), the U.S. Humanitarian Demining Office, and the Thailand Mine Action Centre undertook a cooperative trial of the Pearson Survivable Demining Tractor and Tools with its segmented roller attachment. This trial evaluated the effectiveness of the roller attachment in triggering three different antipersonnel landmines at depths ranging from 0mm to 200mm. In one case a depth of 350mm was used. Two different soil conditions were used: (i) hard, recently de-brushed conditions, and (ii) freshly tilled or loosened soil. This project makes up a part of the ongoing CCMAT efforts at test and evaluation of mechanical equipment for demining operations.

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Résumé

En mars et avril 2003, le Centre canadien de technologies de déminage (CCTD), le bureau de déminage humanitaire américain (US Humanitarian Demining Office) et le Centre de déminage de Thaïlande ont entrepris les essais collectifs du tracteur survivable de déminage Pearson et autres outils comprenant un cylindre segmenté comme attachement. Cet essai évalue l’efficacité de cet attachement à déclencher trois différentes mines terrestres antipersonnel à des profondeurs allant de 0 mm à 200 mm. Une profondeur de 350 mm a été utilisée dans un cas. Deux différentes conditions de sol ont été utilisées : (i) des conditions de sol dur, récemment débroussaillé et (ii) dans des conditions de sol aéré venant d’être cultivé. Ce projet fait partie des efforts de test et évaluation de l’équipement mécanique que le CCDT est en cours d’effectuer pour les opérations de déminage.

DRDC Suffield TR 2003-107 iii

Executive summary

The Pearson Survivable Demining Tractor and Tools (SDTT) with the segmented roller accessory was tested in a cooperative Thai-Canadian-America program along the Thai-Cambodian border in March/April 2003. This test examined the effectiveness of the roller in triggering three types of antipersonnel landmines at depths up to (and in some cases, exceeding) 200mm, in two different soil conditions. The basic Standard Operating Procedure (SOP) used by the Thailand Mine Action Centre (TMAC) at this location was adopted to maximize the degree of realism that could be achieved, while still conducting the trial under controlled, repeatable conditions. Additional data was collected to examine the possibility of the SDTT rubber tires triggering the mines, and also the possibility that human footsteps would be sufficient to trigger the mines.

The roller was found to be highly effective at triggering the PMN mine down to depths exceeding 200mm in both hard and tilled soil conditions. Both the M14 and the Type 72A were far more difficult to trigger, even at relatively shallow depths. In hard soil, depths of 100mm or more were sufficient to prevent the roller from triggering the Type 72A in any significant numbers. The roller was unable to trigger any M14 mines in hard soil at 50mm or deeper. Tilled soil provided slightly better results with triggering of the Type 72A dropping sharply at 125mm (vs. 100mm in hard soil), and at 75mm (vs. 50mm) for the M14.

The overall conclusion is that the SDTT roller, when operated under an SOP similar to that used in the trials, is unlikely to be useful as a demining tool all by itself. Its usefulness in combination with other demining approaches or as an area reduction or a risk reduction tool will depend on individual circumstances including available resources, terrain, vegetation, and possibly even clearance level requirements. Each end user will have to evaluate the results of this trial to determine whether the SDTT segmented roller can be used to advantage in that user’s own operational environment.

This trial was part of the ongoing program of test and evaluation of mechanically assisted clearance equipment by the Canadian Centre for Mine Action Technologies (CCMAT). More details on the program can be found at the CCMAT website (http://www.ccmat.gc.ca).

Coley, G. 2003. Field Testing of the SDTT Segmented Roller. DRDC Suffield TR 2003-107. Defence R&D Canada – Suffield.

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Sommaire

Le tracteur survivable de déminage Pearson et autres outils avec son cylindre segmenté comme attachement a été testé par un programme coopératif entre la Thaïlande, les États-Unis et le Canada, le long de la frontière entre la Thaïlande et le Cambodge, en mars et avril 2003. Ce test examine l’efficacité des cylindres à déclencher trois types de mines terrestres antipersonnel, à des profondeurs allant jusqu’à 200 mm (et quelques fois supérieures), dans deux différentes conditions de sol. La procédure normale d’exploitation (PNE) de base utilisée à cet endroit par le Centre de déminage thaïlandais a été adoptée pour maximiser le degré de réalisme, tout en permettant de continuer les essais dans des conditions contrôlées et reproductibles. Des données additionnelles ont été collectées visant à examiner la possibilité que les pneus en caoutchouc du SDTT déclenchent les mines et aussi la possibilité que les pas humains suffisent à déclencher les mines.

On a trouvé que le cylindre est très efficace à déclencher les mines PMN à des profondeurs supérieures à 200 mm, dans des conditions de sols à la fois durs et cultivés. Les mines M14 et les Types 72 A étaient beaucoup plus difficiles à déclencher, même quand elles étaient relativement peu profondes. Dans les sols durs, les profondeurs de 100 mm ou supérieures suffisaient à empêcher le cylindre de déclencher un nombre signifiant de mines de type 72 A. Le cylindre n’a pu déclencher aucune mine M14 dans les sols durs, à 50 mm ou plus profond. Les sols cultivés ont fourni des résultats légèrement meilleurs, en ne réduisant considérablement les déclenchements qu’à partir de 125 mm (comparé à 100 mm dans les sols durs) et à 75 mm (comparé à 50 mm) pour les M14.

La conclusion générale est que le cylindre SDTT n’est probablement pas très utile en lui-même comme outil de déminage quand il est utilisé selon des instructions permanentes d’opération (IPO) semblables à celles utilisées durant ces essais. Son utilité en combinaison avec d’autres méthodes ou comme outil de réduction de zone ou de réduction de risque dépendra des circonstances individuelles dont la disponibilité des ressources, le terrain, la végétation ou sans doute même des besoins en niveau de dégagement de zones. L’utilisateur final devra évaluer les résultats de ces essais et déterminer s’il est avantageux d’utiliser le cylindre segmenté SDTT dans l’environnement opérationnel propre à cet utilisateur.

Cet essai faisait partie d’un programme de longue durée de test et évaluation d’équipement mécaniquement assisté de dégagement de zone, entrepris par le Centre canadien de technologies de déminage (CCTD). On peut trouver de plus amples détails au sujet de ce programme sur le site Web du CCTD (http://www.ccmat.gc.ca).

Coley, G. 2003. Field Testing of the SDTT Segmented Roller. DRDC Suffield TR 2003-107. R & D pour la défense Canada – Suffield.

DRDC Suffield TR 2003-107 v

Table of contents

Abstract........................................................................................................................................ i

Résumé ....................................................................................................................................... ii Executive summary ................................................................................................................... iii Sommaire................................................................................................................................... iv Table of contents ........................................................................................................................ v List of figures ........................................................................................................................... vii Acknowledgements ................................................................................................................... ix 1. Introduction ................................................................................................................... 1

1.1 Background ...................................................................................................... 2 1.2 The Equipment ................................................................................................. 2 1.3 The Trial Team................................................................................................. 3 1.4 The Trial Location............................................................................................ 3 1.5 The Targets....................................................................................................... 4

1.5.1 The Monitor......................................................................................... 4 1.5.2 The Mines............................................................................................ 5

1.6 Notes on Terminology...................................................................................... 9 2. Test Methodology........................................................................................................ 11

2.1 Basic SOP....................................................................................................... 11 2.2 Target Layout ................................................................................................. 11 2.3 Burial Depth ................................................................................................... 15 2.4 Burial Technique ............................................................................................ 16 2.5 Soil Hardness and Moisture Content .............................................................. 18 2.6 Mine Orientation and Other Limiting Conditions .......................................... 19

2.6.1 Mine Orientation ............................................................................... 19 2.6.2 Terrain Irregularities.......................................................................... 19 2.6.3 Ground Anomalies ............................................................................ 19 2.6.4 Limiting Conditions .......................................................................... 20

3. Trial Conduct and Treatment of Data.......................................................................... 21 3.1 Roller tests ...................................................................................................... 21 3.2 Tire tests ......................................................................................................... 22 3.3 Footstep Tests................................................................................................. 23

3.3.1 Footsteps Alone................................................................................. 23 3.3.2 Footsteps After Roller ....................................................................... 23

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4. Test Results and Discussions....................................................................................... 24 4.1 Roller Results ................................................................................................. 24

4.1.1 Hard Soil............................................................................................ 24 4.1.1.1 PMN in Hard Soil .............................................................. 24 4.1.1.2 Type 72A in Hard Soil ....................................................... 27 4.1.1.3 M14 In Hard Soil ............................................................... 29 4.1.1.4 Hard Soil – Effects of Terrain Irregularities ...................... 31 4.1.1.5 Hard Soil – Anomalous Data ............................................. 32

4.1.2 Tilled Soil .......................................................................................... 32 4.1.2.1 PMN in Tilled Soil ............................................................. 33 4.1.2.2 Type 72A in Tilled Soil...................................................... 35 4.1.2.3 M14 In Tilled Soil.............................................................. 37 4.1.2.4 Tilled Soil – Effects of Terrain Irregularities..................... 39 4.1.2.5 Tilled Soil – Anomalous Data............................................ 40

4.2 Tire Results..................................................................................................... 41 4.3 Footstep Results ............................................................................................. 42

4.3.1 Footsteps Alone................................................................................. 43 4.3.2 Footsteps After Roller ....................................................................... 44

5. Conclusions ................................................................................................................. 47 5.1 Roller Effectiveness........................................................................................ 47

5.1.1 Effectiveness in hard soil................................................................... 48 5.1.2 Effectiveness in tilled soil ................................................................. 48 5.1.3 Overall Roller Effectiveness.............................................................. 49

5.2 Tire Strikes ..................................................................................................... 49 5.3 Foot Strikes Alone.......................................................................................... 50 5.4 Foot Strikes After The Roller ......................................................................... 50

6. Recommendations ....................................................................................................... 51 Annex A – Raw Trial Data ....................................................................................................... 53

Annex B – Trial Photographs ................................................................................................... 99 Annex C – Equipment Supplementary Data........................................................................... 113

List of symbols/abbreviations/acronyms/initialisms .............................................................. 116 Glossary.................................................................................................................................. 117

DRDC Suffield TR 2003-107 vii

List of figures

Figure 1. Pearson SDTT With Segmented Roller ...................................................................... 3 Figure 2. EDRIFT Monitoring Circuit, Cable, Switch And M14 Mine ..................................... 5 Figure 3. PMN............................................................................................................................ 6 Figure 4. Type 72A..................................................................................................................... 6 Figure 5. M14 Mine.................................................................................................................... 7 Figure 6. Untriggered M14 Mine with Partially Pressed Pressure Plate .................................... 8 Figure 7. Type 72A Pressure Plate – Underside......................................................................... 9 Figure 8. Mine Lane Layout ..................................................................................................... 12 Figure 9. Machine Passes 1 & 2 ............................................................................................... 12 Figure 10. Machine Passes 3 & 4 ............................................................................................. 13 Figure 11. Machine Passes 5 & 6 ............................................................................................. 14 Figure 12. Machine Passes 7 & 8 ............................................................................................. 15 Figure 13. Depth of Burial Illustration – Type 72A at 200mm ................................................ 16 Figure 14. Hole Bridging By Roller (Idealized for PMN)........................................................ 18 Figure 15. Effectiveness Against PMN in Hard Soil................................................................ 26 Figure 16. Effectiveness Against Type 72A in Hard Soil ........................................................ 28 Figure 17. Effectiveness Against M14 in Hard Soil................................................................. 30 Figure 18. Effectiveness Against PMN in Tilled Soil .............................................................. 34 Figure 19. Effectiveness Against Type 72A in Tilled Soil....................................................... 36 Figure 20. Effectiveness Against M14 Mine in Tilled Soil...................................................... 38

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List of tables

Table 1. Effectiveness Against PMN in Hard Soil ................................................................... 25 Table 2. Effectiveness Against Type 72A in Hard Soil............................................................ 27 Table 3. Effectiveness Against M14 in Hard Soil .................................................................... 29 Table 4. Hard Soil – Terrain Irregularities ............................................................................... 31 Table 5. Hard Soil – Anomalous Data...................................................................................... 32 Table 6. Effectiveness Against PMN in Tilled Soil ................................................................. 33 Table 7. Effectiveness Against Type 72A in Tilled Soil .......................................................... 35 Table 8. Effectiveness Against M14 Mines in Tilled Soil........................................................ 37 Table 9. Tilled Soil – Terrain Irregularities.............................................................................. 39 Table 10. Tilled Soil – Anomalous Data .................................................................................. 40 Table 11. Tire Strike Tests – Hard Soil .................................................................................... 41 Table 12. Tire Strike Tests- Tilled Soil .................................................................................... 42 Table 13. Footstep Tests in Hard Soil– No Roller.................................................................... 43 Table 14. Footstep Tests in Tilled Soil – No Roller ................................................................. 44 Table 15. Footstep Tests in Hard Soil – After Roller ............................................................... 45 Table 16. Footstep Tests in Tilled Soil – After Roller ............................................................. 46

DRDC Suffield TR 2003-107 ix

Acknowledgements

A trial of any description takes many people to ensure success. An international trial such as this one requires even more people and even greater cooperation and flexibility. We were rewarded in this program with a number of people who contributed greatly to the success of the project.

The trial of the Pearson Survivable Demining Tractor and Tools (SDTT) segmented roller involved a machine built in the United Kingdom, purchased by Americans, operated by Thais and tested by Canadians. The only ones not directly involved in the trial were the manufacturers. The American Humanitarian Demining Program Office (HDPO) provided not only permission to use the machine for testing, but also enthusiastic support and assistance, especially in the preparation and planning stages. Mr. Charlie Chichester and Maj. Noy Rovira were particularly visible and helpful in the early stages. Political and military activities which occurred at the time of the trials unfortunately prevented Major Rovira from being a part of the field trial team. Mr. Jim Yoder, stationed at the test site, provided a contact with the HDPO during the trial, and also provided essential machine maintenance support and trial assistance.

Without the active participation of Mr. Dave McCracken, the trial never would have been started. Mr. McCracken was instrumental in ensuring that the arrangements with the Thailand Mine Action Centre (TMAC) were made correctly, and that the trial team understood the requirements of TMAC. His able assistance in the office and in the field, and his enthusiasm for the project were invaluable. Ms. Chalermluck Thanapanich, who provided logistics support and consultancy services for the team, went well beyond the terms of her contract ensuring that the many background details were taken care of. She was also a key player in arranging things before the trial team arrived in Thailand.

The TMAC staff at Humanitarian Mine Action Unit #1 (HMAU1) deserves special thanks. Close to a dozen workers could be found on any given day digging holes, burying test pieces, helping with the trials, and going about any number of other tasks in the 40°C+ heat. All of them conducted themselves in a professional, friendly manner, and made dealing with TMAC a pleasure for the visiting Canadian team. The support of their commanding officers in providing the people, equipment and resources necessary for the trial is greatly appreciated.

Mr. Leonard Kaminski, the Mechanical Studies Specialist from the Geneva International Centre for Humanitarian Demining, attended the first week of trials. Not content to be an idle observer, Mr. Kaminski participated fully in all aspects of the work from digging holes to burying targets, collecting data and stomping on the mechanical reproduction mines. In off-hours, he provided the team with valuable insights into what was happening with the segmented roller in other demining operations around the world. By sharing his experience in the world of demining, he helped ensure that the team viewed the trials from as broad a perspective as possible.

In a similar manner, Mr. Johan Van Zyl of the Japan Alliance for Humanitarian Demining Support was a help to the team. Although Mr. Van Zyl was fully occupied with a demining operation a few kilometres away, he paid frequent visits to the trial

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site to see how things were going. In addition to ‘getting his hands dirty’ on our trials when he had a little extra time, Mr. Van Zyl was another valuable source of experience and information for the team. Like Mr. Kaminski, he was able to give the team a broader view of the world of demining, and especially roles for mechanical equipment in that world. His good natured approach and, freely shared contributions were welcomed and valued.

The Canadian Embassy staff in Bangkok was superb in its support of the program. From the first message informing the embassy of the pending visit, the embassy offered all of the assistance the trial team could possibly have asked. Col. Gene Pestell and Sgt. Susan Jimmo ensured that the team and test equipment had no difficulties getting into and out of Thailand smoothly. Mr. Alexandre Lévêque and Ambassador Andrew McAlister showed a keen interest in the project, made time for pre and post-trial briefings and offered assistance in the delivery of the report. The entire team was very impressed by the embassy staff’s attitude and willingness to extend whatever assistance was needed.

The support of managers and supervisors at Defence R&D Canada – Suffield, and the Canadian Centre for Mine Action Technologies was necessary and appreciated from the initial concept through to the final report. The complications introduced by conducting the trial across a fiscal year end, and with a change of personnel were handled in a positive and constructive manner by Mr. Al Carruthers, Dr. Chris Weickert, Dr. Bob Suart, and Maj. Kent Hocevar. The cooperation of Dr. John McFee in making Mr. Wayne Sirovyak available for the project is also very much appreciated.

Finally, the contribution of Mr. Wayne Sirovyak of DRDC-Suffield must be highlighted. Mr. Sirovyak was responsible for the design, assembly and testing of the Electronic Detonator Replacement and Interrogation of Fuze Triggering (EDRIFT) system which figured so prominently in this trial. In addition to developing the electronics, Mr. Sirovyak provided extensive consultation and assistance in planning the trials, and was an essential member of the trial team. His active participation both in Canada, and in Thailand, was key to the success of the roller trials, the EDRIFT system development, and the redesign of the mechanical reproduction mines to be more useable in equipment trials.

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1. Introduction

Over the past decade, there have been many attempts to introduce mechanical mine clearance equipment to humanitarian demining. Early on, it was hoped that such equipment would replace manual demining, but it was soon realized that the technology could not reliably meet the high quality standards of humanitarian demining. At the same time, it was found that in some cases, if mine clearance machines were used to prepare the terrain prior to manual demining, the latter could be done in significantly less time. Thus was born the concept of Mechanical Assistance to manual demining. Some functions that are particularly well suited to mechanical equipment are the removal of vegetation and trip wires or the break-up and processing of the soil.

Private companies, Non-Governmental Organizations (NGOs), universities and government-sponsored organizations, have since proposed a broad range of Mechanically Assisted Clearance Equipment (MCE). Often, this equipment is developed from intuition, experience and observations. Rarely has the effectiveness of the machine ever been proven in a scientifically defensible manner.

The Canadian Centre for Mine Action Technologies (CCMAT) has engaged in two separate series of trials of mechanical equipment. In the summer of 2000 four machines were tested, one of which was eventually taken for field trials in Thailand with the Thailand Mine Action Centre (TMAC), and was subsequently donated to TMAC by the Canadian government. The second series of trials, conducted in the summer of 2002, two machines were tested. Testing on a third device, a segmented roller, was started, but testing was halted for several reasons.

The roller was selected as it represented a type of equipment which is in use around the world, but whose effects against landmines have not yet, to the author’s knowledge, been quantified. Ordinarily, CCMAT takes the approach that a machine should be tested at home, and should only be taken for field trials if the at-home trials show that the machine has some hope of being effective in demining operations. In stopping the tests, it was reasoned that, no matter what the results, field testing would be necessary; if the at-home trials showed very good results, the sceptics could rightfully complain that these were sandbox tests which do not fully reproduce the more difficult real-world conditions of a minefield. On the other hand, with poor at-home results, the machine manufacturer or other fans of the roller might well claim that their field experience has shown very different results. Thus, since the machine is already being used in many places, field trials would be required to verify the at-home trials no matter what results the at-home trials produced. With that in mind, the at-home trials were halted, and efforts were focused on performing controlled, repeatable, statistically useful tests in a field-test scenario.

The positive relations developed during the previous CCMAT-TMAC program were put to good use in designing a cooperative trial to evaluate the Pearson Survivable Demining Tractor and Tools (SDTT) with its segmented roller attachment, on which the in-Canada equipment had been based.

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1.1 Background Rollers of various sorts have been used against landmines for years. Many of the applications are focused on military operations, for which the requirements may be very different from those for humanitarian demining. Rollers for humanitarian demining are generally smaller and lighter than their massive military cousins. Generally, humanitarian demining rollers are intended for use against antipersonnel mines rather than the antitank mine targets targeted by military rollers.

The segmented roller tool provided for the Pearson SDTT is typical of rollers used in humanitarian demining operations around the world. Unfortunately, like many other humanitarian demining equipment, this roller suffers from a lack of performance data. Very little information exists which quantifies the effectiveness of the roller against different types of mines, in different types of soil, or at different depths of burial. This can have several negative consequences:

• An organization may use the roller without really understanding what effect it is having, and may therefore draw inaccurate conclusions about the presence of mines.

• Without any hard data on the effectiveness of the roller, an organization may use it to excess, which wastes resources (time, maintenance, money, etc).

• Without any hard data on the effectiveness of the roller, an organization may use it in a manner which is ineffective (insufficient number of passes, too high a speed, etc).

• An organization may decide not to use the roller since its effects are unknown. The machine would therefore lie idle whether it is useful or not.

This test program was conceived to provide specific data on the effectiveness of the Pearson SDTT segmented roller under a defined set of conditions. Clearly it would be desirable to create a full set of data which defined the effectiveness against all types of mines at all depths in all possible soil conditions. Clearly this is impractical. The test program documented herein examined three mine types at depths up to 200mm in two soil conditions found at TMAC HMAU1 in eastern Thailand.

1.2 The Equipment The equipment selected for this trial program is the segmented roller tool from the Pearson Survivable Demining Tractor and Tools shown in Figure 1. This tool consists of a series of steel disks mounted on an axle. Each disk is free to float vertically, independent of its neighbours, in order to accommodate minor irregularities the terrain. Detailed information on the SDTT and the roller are available from many sources include Pearson Engineering (the manufacturer), the US Humanitarian Demining Program Office (the owner), and also from the Mechanical Demining Equipment Catalogue 2003 published by the Geneva International Center for Humanitarian Demining (www.gichd.ch).


Figure 1. Pearson SDTT With Segmented Roller

1.3 The Trial Team The original trial team included personnel from the CCMAT, TMAC, and HDPO. The equipment, originally manufactured in the United Kingdom by Pearson Engineering was purchased by the Americans and has been under test with TMAC for some time with funding provided by HDPO. In addition to providing the equipment, HDPO was to provide personnel to assist with the trials. Unfortunately, the timing of the trials coincided with the start of military operations in Iraq, and the US team was prevented from attending. The American team was represented by Mr. Jim Yoder, already stationed at HMAU1, who provided valuable field assistance during the trials, and also reported back to the HDPO on a regular basis.

1.4 The Trial Location The trial was conducted at the TMAC Humanitarian Mine Action Unit #1 (HMAU1) along the Thai-Cambodian border just north of Aranyaprathet. This location, the home base for the equipment in question, was previously used in CCMAT/TMAC trials of the ProMac BDM48 with great success. The national infrastructure (roads, fuel and parts supply, communications, etc) and the TMAC organization at this location provided ideal conditions in which to conduct the trials. Another significant factor, not to be minimized, is the support provided by the front-line TMAC personnel at HMAU1. Previous experience showed the TMAC personnel to be enthusiastic, motivated, energetic and reliable. This was demonstrated again in this trial program and was a key to the success of the trial.


1.5 The Targets

1.5.1 The Monitor In order to evaluate the effectiveness of a machine, it is necessary to use tools which provide repeatable, reliable, realistic data, in quantities large enough to say something significant. Using a single Russian PMN-4 mine will provide reliable and realistic data for that type of mine, but it may not be a good choice because (a) it has very rarely, if ever, been seen in minefields, and (b) the quantity makes the data almost meaningless. On the other hand, a mine like the Russian PMN, is found in many places around the world. Using dozens or hundreds of real PMN mines in a trial program would give data which is repeatable, reliable and realistic, and in quantities to make the data of value. The addition of other, different types of mines would extend the data beyond a single type, and make the trial of still greater value. Unfortunately, using real mines in a trial is fraught with difficulties. The risks to both humans and machines in such a trial can be significant, the time required to conduct the trials safely may be considerable, and the availability of mines in these days of the landmine ban can make such trials difficult.

On the other end of the spectrum, some people suggest that inert, non-functional ‘pucks’ make useful test targets. While these devices may have some use in certain applications, the data provided is of dubious value, no matter how many targets are provided. They may provide occasional witness to physical contact between the machine and the mine, but there is no realistic indication of damage or mine triggering.

To overcome some of these difficulties, CCMAT has worked toward inert, functional replacements for mines, and ways to use any available mines in safe, effective ways. The mechanical reproduction mine system, developed over the past few years, offers many benefits over trials using either pucks or real mines, but there are some problems with the system that limit its use. Recently CCMAT has developed a new system known as the Electronic Detonator Replacement and Interrogation of Fuze Triggering (EDRIFT). This simple, inexpensive system allows testing with a variety of real mines without detonators, and also with modified bodies from the mechanical reproduction mines.

A prototype of the EDRIFT system, shown in Figure 2, was used with great success in these SDTT roller trials with real M14 mines and with modified PMN and Type 72A mechanical reproduction mine bodies. All three types are common threat mines around the world, and all three were used in quantities sufficient to make the data meaningful.


Figure 2. EDRIFT Monitoring Circuit, Cable, Switch And M14 Mine

1.5.2 The Mines The three mine types used in this trial included the Russian PMN, the Chinese Type 72A and the American M14. Mechanical reproduction mine bodies were modified to use EDRIFT for the PMN and Type 72A, while the M14 targets were real mines without detonators. These three targets, along with the real PMN and Type72A mines are shown below in Figure 3, Figure 4 and Figure 5.

These targets present a useful cross section of mines to use in tests such as this. The PMN is a large mine with a large pressure plate. It presents a relatively easy-to-trigger mine, and it is found in many places around the world. The Type 72A is also widely distributed in minefields around the world, but it is much smaller and more difficult to trigger, with the smaller pressure plate. It also has a completely different mechanical fuzing mechanism. The M14 is useful in at least three respects. First, it is slightly smaller than the Type 72A and represents a target which is easy to miss. Second, the M14 has a very small pressure plate and is difficult to trigger if not pressed just right. Finally, the M14 is close to the same size and has a fuze mechanism very similar to the Type 72A, which makes it useful as a confirmation tool to validate the Type 72A Mechanical Reproduction Mine.


PMN Mine

(shown for reference)

PMN Mechanical Reproduction Mine Body

Figure 3. PMN

Type 72A Mine (shown for reference) Type 72A

Mechanical Reproduction Mine Body

Figure 4. Type 72A


M14 Mine M14 Mine Detonator Well

Figure 5. M14 Mine

It was decided that the Type 72A mechanical reproduction mine bodies would be used repeatedly proving that they did not display any damage. The springs were evaluated prior to the trials by cycling 6 new springs thirty times from rest to reversed and back again using a Lloyd Instruments LR30K tension/compression testing machine. These tests showed that in the first 5-10 cycles the springs lost about 2-3% of their original strength, and that by the 30th cycle, they had lost less than 5%. It was therefore concluded that it would be appropriate to reuse the springs up to 30 times providing that they did not show any signs of cracking. Minor surface flaws were acceptable as they had shown up in the 30-cycle tests without any apparent effect on strength.

The same question was raised for the M14 mines. Could they be reused? It was quickly decided that they would be reused as long as they had not been triggered. After being triggered once, they would be retired from the tests. There was no way to evaluate whether the M14 springs were cracked, broken, weakened, or otherwise damaged, and so they were assumed to be only suitable for a single triggering event. Once triggered they were marked with a paint spot, and set aside for destruction after the trials were complete.

The PMN mechanical reproduction mine bodies use only coil springs and so the above concerns would not apply until several tens of thousands of cycles had occurred. Again, they were to be reused as long as no damage was apparent.

A comment was made above to the effect that the M14 is difficult to trigger if not pressed properly. This was illustrated in one of the tests of tire strikes against M14 mines. An M14 was buried at 0mm (with the top of the mine flush with the ground surface) and the SDTT tire driven over the mine. Because of the tread pattern on the tire, the tire tread only made partial contact with the M14 pressure plate. Figure 6 shows the result, in which the pressure plate was fully depressed on one side, but not on the other side. This


mine was not triggered. The tire was driven over the mine twice more without triggering the mine. After the third tire strike the mine was carefully removed and inspected. The high point on the pressure plate was then pressed lightly by hand and the fuze mechanism triggered. The point is that even when M14 mines are located right at the surface, they may not trigger properly if they are not pressed exactly right.

Figure 6. Untriggered M14 Mine with Partially Pressed Pressure Plate

A commonly asked question is why no tripwire activated mines are used in the tests. There are two main answers to this question. The first is that the roller is a machine intended to press down on mines, not one designed to pull tripwires. It would be analogous to asking why vegetation clearance abilities were not tested. The machine might well pull a few tripwires, but that is not its purpose.

The second reason relates to the TMAC Standard Operating Procedure (SOP) on which this trial was built. The SDTT is used on a piece of land with a vegetation slasher, a mower, a magnet, and possibly a vegetation/slash rake or scoop before the roller is used. The application of these tools along with the wheel/soil interactions through all of these operations is almost certain to take down any existing tripwires well before the roller enters the scene. The effort involved with doing tripwire tests would be disproportionate to the likelihood of encountering tripwires with the roller under this SOP. It might have been useful to test the tripwire removal capability of the SDTT with the other tools (used before the roller), but that was outside the scope of this trial.

Following the trial a discovery was made which showed a difference between the Type 72A mechanical reproduction mine body and a real Type 72A mine. As shown in Figure 7, the underside of the pressure plates are subtly different. The real Type72A has three alignment lugs while the mechanical reproduction mine body has only one. This is not considered significant. The other difference, which may be slightly more significant, is the presence of a


central post on the mechanical reproduction mine body pressure plate. This may make it slightly easier to trigger the mechanical reproduction mine body since the pressure will be applied to the peak of the Belleville spring. The actual load required to trigger the mechanical reproduction mine body is still accurate, but the central post make it slightly more tolerant of off-centre loading. It is possible that a point loading system (including the human footsteps, for example) might have somewhat different results if the point load is not applied right in the centre of the pressure plate. Since the roller disks spanned considerably more than the entire width of each mine/reproduction mine, and applied the load more or less uniformly across the pressure plate, it is not considered that the central post will have any effect on the data.

Type 72A Pressure Plate (Inside View) Real Mine

Type 72A Pressure Plate (Inside View) Mechanical Reproduction Mine Body

Figure 7. Type 72A Pressure Plate – Underside

1.6 Notes on Terminology For the sake of convenience, some liberties are taken with terminology in this report. The term ‘minefield’ may, to many people, be taken to mean a defined area, with clear, marked boundaries, while a ‘mined area’ would mean an unmarked area of uncertain boundaries. Without arguing the point either way, the term ‘minefield’ is used herein as an inclusive term that simply defines a piece of land suspected of containing mines, whether there are marked boundaries or not.

For the purposes of this report, ‘mine’ and ‘landmine’ are used to refer only to antipersonnel mines unless they are explicitly defined as antitank mines. The terms ‘mine,’ ‘mechanical reproduction mine (body)’ and ‘target’ are used more or less interchangeably to describe the device used in the test. When a mechanical


reproduction mine body was used in the test, and the term ‘mine’ is used in the discussion, there is the implicit understanding that a test against a surrogate can never have absolutely perfect fidelity with a test against a real mine.

Depth of burial (DOB) is a very important term defined below in section 2.3 which always refers to the distance from the soil surface down to the upper surface of the mine pressure plate.

In describing the soil used for the tests, the terminology is informal. As noted below in section 2.5, we were unfortunately unable to take quantitative measurements of the soil conditions. In qualitative terms, the ‘hard’ soil conditions are those which most nearly match the conditions for a real minefield in this area. The tilled soil had been loosened to a depth of 100-150mm using one of the other SDTT tools. The term ‘tilled’ soil is not strictly accurate either since the tool used to work the soil was actually a harrow. In the raw data provided in Annex A, the term ‘soft’ was used as a convenient shorthand to described the tilled/harrowed soil.

Finally, the term effectiveness is used rather than ‘performance.’ Performance may include many different aspects of a system’s operation such as fuel consumption, speed of operation, maintenance and repair time, along with the ability to trigger mines. For the purposes of this report ‘effectiveness’ is used only with reference to the ability of the machine to trigger the target landmines.


2. Test Methodology

2.1 Basic SOP The test methodology was based on the area reduction SOP used by TMAC for the SDTT. The SOP has the vegetation cut and mowed to a condition where the soil is exposed but essentially intact. Vegetation stubble may remain along with some debris, although the bulk of the cut vegetation is removed. At this point the roller is first used. It is pushed or pulled across the area in such a manner that a mine would be approached from 8 different directions. Following this, the soil is tilled, or harrowed to a depth ranging up to 200mm, depending on soil conditions, whereupon the roller is applied in the same pattern as before. Other tasks are conducted during the overall operation, but these are the ones which involve the roller.

This approach was adopted for several reasons. First, it provided two soil conditions to test. Second, it provided the opportunity for 8 separate passes of the machine in each soil condition. Third, it provided these conditions in a scenario which was highly realistic, and representative of the method employed in a real demining operation. An additional benefit is that testing with this SOP provided supporting data to TMAC to allow them to verify or modify their SOP as necessary without compromising the data in any way.

2.2 Target Layout With the basic SOP established, the ‘mine lane’ was laid out as shown in Figure 8. This shows the targets laid out in groups of four along a line. The depths indicated were used as a starting point, and were varied as the trial evolved.

The first pass of the machine was along the long axis of the pattern, with the second pass in the opposite direction. The third pass was run at 90° to the first two and centred on one group of four mines (MRMs). The fourth pass simply reversed direction over the same group of four targets. The fifth and sixth passes were run on one diagonal, and the seventh and eighth passes used the other diagonal. This sequence is shown below in Figure 9 through Figure 12. The machine was then moved along to the second group of four targets and testing on that group resumed at the third pass. The process was continued with each group of four targets until the whole lane was completed. Of course, testing on a particular group of four was discontinued if all four targets had been triggered. Sometimes this occurred on the first pass, and sometimes it did not occur even after all 8 passes.


Figure 8. Mine Lane Layout

Figure 9. Machine Passes 1 & 2



2.3 Burial Depth Initially each group of four targets was placed at one depth, with each following group at a different depth. This allowed a single lane to provide four data points at 0, 25, 50, 100, and 200mm depths of burial. As testing proceeded the depths were sometimes adjusted to provide data at some intermediate depth. The depth pattern was sometimes adjusted to simplify and speed up mine (MRM) burial operations.

Note that in all cases, depth, burial, depth of burial, and DOB refer to the depth as measured from the ground surface down to the upper surface of the mine or the


pressure plate of the mine. This is shown in Figure 13 for a Type 72A mechanical reproduction mine body at 200mm.

An often asked question is why such deep depths are used. It is true that most mines are buried at no more than 25 or perhaps 50mm, but many mines of all types are found at deeper depths due to erosion, soil movement, vegetation effects, and the like. Two hundred millimetres was selected since it is the maximum depth most often used in discussions or specifications. It is quite valid to point out that if mines can migrate to 200mm, they might equally well migrate to deeper depths. First, an arbitrary line had to be drawn somewhere, and second, a small additional set of trials at deeper depths was, in fact, conducted for the PMN model.

Figure 13. Depth of Burial Illustration – Type 72A at 200mm

2.4 Burial Technique As a mine sits in the soil for a time, the soil gradually settles, compacts, and bonds with the soil around it. This can easily be seen when one compares the hardness of agricultural ground that is worked every year with ground that is left untouched for many years. It takes several years, but eventually the untouched soil can become hard and uniform, including small spots which might have been disturbed years before.


Moisture, temperature and vegetation may play a significant role in accelerating or modifying the pace. After many years of soil settling, the soil above a mine may be indistinguishable from the surrounding soil. This would be the ideal case to use for testing but it is simply not possible to replicate this for most tests.

When a buried mine is laid, it is most often placed in an oversized hole to maximize the chance of a foot setting off the mine. That is, the smaller the diameter of the hole, the greater the chance that the foot could bridge across the hole and fail to trigger the mine. As the soil compacts over time, the loose soil above and around the mine gradually bonds with the surrounding soil and the oversized hole ceases to exist. Similarly, a shallow buried, or surface laid mine which ends up at a deeper depth has the same conditions in which, over time, the surrounding and covering soil compacts and bonds together to form a uniform condition.

There are two extremes in the soil conditions that can be considered. The first is in the case of a newly buried mine where there is a large area of soft soil. The large soft area prevents bridging and the soft soil compresses and deflects easily. Since the soft soil deflects and compresses easily, it is almost like starting with a shallower depth of burial, where the machine is probably more effective.

At the other end of the scale is the ‘weathered-in’ condition where there is only elastic deformation (little or no permanent deflection of the soil), and where the soil above the mine must be sheared to allow it to move downward and depress the pressure plate of the mine.

In testing, the goal was to approach the ‘weathered-in’ condition as closely as possible. Unfortunately, the actual conditions would be closer to ‘newly-buried.’ The solution adopted for these trials was as follows.

• The soil surrounding the mine was left intact and undisturbed as much as possible. The holes were made as small in diameter as possible to prevent the ‘big, soft, hole’ effect. This is shown above in Figure 13 for a Type 72A mechanical reproduction mine body being dug in at 200mm.

• Where possible, the soil was compacted by hand during burial to make it as close as possible to the original conditions. In the harrowed soil this was a reasonably good approximation to the condition of the surrounding soil, but in the hard soil, it was simply the best that could be done.

• Hand compaction of the soil was possible for the Type 72A and the M14. Compacting the soil over the PMN always triggered the target, so the PMN was simply covered with loose soil.

Given that the soil above the mine could not be returned perfectly to the weathered-in condition, there was the potential for bridging across the hole. Figure 14 shows an idealized description of this. For the PMN, the roller might penetrate the hole by as little as 25mm, as shown in Figure 14. If the soil compaction and soil movement achieved by this roller penetration proved inadequate to trigger the mine, it is possible that the roller would simply bridge across the hole without triggering the mine. With the smaller diameter hole used for the M14 and Type72A, the roller penetration would be less than for the PMN. Unfortunately, there is no way to know whether the roller


would have been effective in perfect, weathered-in conditions. This is simply an unavoidable limitation of the test.

Figure 14. Hole Bridging By Roller (Idealized for PMN)

2.5 Soil Hardness and Moisture Content The plan was to have soil hardness and moisture content measured during the trials. The equipment to make these measurements was to have been provided by the American members of the test team but, as noted, the American team was unavoidably prevented from attending the trials. Unfortunately, the timing of events prevented the necessary equipment from being available for the trials, and these soil parameters could not be quantified.

While a measured, quantitative description would obviously be preferred, the hardness of the ‘hard’ soil can be qualitatively described by referring to some of the photographs in Annex B which show the tools used to dig the holes for the mines. Using these hand tools, the soldiers, all in good physical condition, had to work very hard indeed, repeatedly driving the tools into the soil to cut and loosen it. Rods, screwdrivers and other sharpened implements were regularly used, and still, the 200mm holes could easily take 10-15 minutes to complete. To compare, similar holes in the tilled soil would take only 3-4 minutes, and most of that time was spend trimming the hole for depth. Of course, part of the time for the hard soil holes was also dictated by the need to make small, precise holes with accurately measured depths.


2.6 Mine Orientation and Other Limiting Conditions

2.6.1 Mine Orientation It is quite possible that mines may end up in positions with the pressure plate pointing other than straight up. Assuming that a roller can trigger a mine when properly oriented, its triggering ability will degrade as the mine is roller more and more onto its side. With the pressure plate at 90° to the vertical (the mine on its side), there is virtually no chance of any roller triggering the mine. This effect will vary depending on mine type, depth of burial, and soil conditions. There may also be other factors influencing the performance. While it might be desirable to investigate this, it would be exceptionally time consuming and labourious. The time, energy, resources and money required to investigate this effect were considered disproportionate to the benefit gained, and so it was simply acknowledged as a limiting condition.

2.6.2 Terrain Irregularities In a similar vein, there are many limiting conditions of terrain which might affect the performance of the roller. Terrain irregularities of sufficient size to prevent full contact of the rollers would certainly affect the performance. This might be on a small scale with ridges and furrows affecting individual segments of the roller, or it might be larger rises or dips which tip the vehicle enough to prevent the entire roller from touching the ground properly. Simple geometry will show what conditions will actually prevent roller contact with the soil, but there may be some conditions in which the roller, or a segment of the roller, is touching the ground without full contact. This is likely to be a transient condition which will be immediately replaced by a full contact or a no-contact condition, but in any case it will depend greatly on soil conditions. Attempting to quantify the effectiveness of the roller against different mines at different depths in different soils in these limiting conditions would be even more difficult than the mine orientation problem discussed above. Instead, it was recognized that, in order for the roller to work properly, it must be used in conditions where the roller segments are able to fully contact the ground. If conditions in a particular spot are such that the roller segments are not able to contact the ground properly, that spot should be assumed to have been completely missed by the roller and checked by other means. The use of the machine must be properly planned and supervised to ensure that this is accomplished.

2.6.3 Ground Anomalies Finally, there may be conditions in which the mine is in the correct orientation and in which the rollers are making full contact with the ground but where other factors influence the effectiveness. One example noted in the trials is where a mine was located immediately beside or even in the middle of a cluster of bamboo roots. In this situation the roller may easily ride over the root mass (even without significant above-ground stubble) and bridge


across above the mine without triggering it. Again, the machine must be used intelligently to deal with such conditions.

2.6.4 Limiting Conditions In summary then, there are limiting conditions which can easily degrade the performance of the roller. It takes intelligent use of the machine and intelligent assessment of the ground conditions, both before and after the roller, to evaluate possible locations where this may occur, and these locations should be evaluated as if they were not rolled at all. Generally these locations will be small and localized compared with the rest of an area, and this does not negate the effects that the roller might have had on the rest of the area. If a particular area has too many of these trouble spots, it may not be a suitable area for application of the machine.


3. Trial Conduct and Treatment of Data

The raw data from the trials is provided in Annex A. As noted on the test sheets, occasional data points had to be omitted, but these were very few, and do not significantly affect the results. Generally these deletions were caused by malfunctions of the test equipment, or by having run over a target with the tire of the vehicle rather than with the roller. All of the deleted data is listed separately along with explanations for each case. Photographs which illustrate the trial are included in Annex B. Annex C contains supplementary dimensional information that, while not used in this report, may be of some use or interest to the reader.

With the exception of the deleted data points, there are generally 16-20 or more points at each depth, in each soil condition for each mine type. Added to the roller data were several dozen data points where the vehicle tire was used to drive over the target, and several hundred more data points in which untriggered targets were stepped on up to 8 times each. Finally, a set of tests were conducted in which only footstep effects (e.g. no roller) were considered. Combining the roller, tire and foot-strike data, over 3500 individual data points are represented. Data reflecting the tire strikes and footstep effects are summarized but interpretations are minimal. Only those relating to the roller tool itself are examined in great detail. This amounts to over 670 individual targets representing over 2400 separate data points.

3.1 Roller tests Of the almost 700 mine targets used for the roller tests, a few had to be omitted from the data for reasons which are identified below. A small number of additional targets were added to the planned depths in specific cases; the PMN was seen to be triggered down to 200mm, and so a few additional tests were conducted at even deeper depths of burial. The team did not collect significantly useful numbers of data points in these conditions, but simply enough to be able to make some general observations.

The data for the roller is presented as follows.

• First, the two soil conditions are presented separately. The condition described as 'hard soil' refers to ground which has had the vegetation slashed and mowed but where the ground has not been engaged by the machine to any real extent. There may have been locations where a mower blade shaved off a small mound, but these spots were excluded from the test areas. Included, however, were such locations as bamboo stubble, where a thicket had been mowed to ground level. As will be seen, this could influence the roller effectiveness numbers. These conditions are specifically identified but they are included in with the rest of the data. This was the compromise between perfectly consistent, repeatable, laboratory conditions (good statistics) and perfectly representative, real-world minefield soil conditions (good realism). The second soil condition, the 'tilled' soil, is that after the ground had been tilled with the SDTT harrow attachment. Depending on the exact local conditions, this meant that the soil had been tilled to a depth between 100mm and 150mm. It also meant that the soil surface was irregular. Again, this was accepted as a compromise between laboratory


conditions and realistic conditions. The actual soil in both 'hard' and 'tilled' areas was as close to identical as field conditions allowed. The various test plots were all within 100 metres of each other.

• It should be noted that every set of targets in the tilled soil was set up in a new set of holes where the soil was freshly tilled and untouched by tire or roller. The soil at the hole locations was levelled to provide a 'top-of-hole' reference from which to measure. In the case of the hard soil, the same holes were reused several times as long as the hole walls had not started to collapse. Visual observations of the hard soil before and after the roller showed that the soil appeared to be acting almost entirely elastically. That is, it did not seem to take on any permanent deformation except for a 1-2mm deep footprint or track. The time needed to dig new holes in the hard soil for each set of tests would have slowed trial progress to a crawl since the soil was extremely hard and digging very slow and difficult. All things taken into account, it was decided that the clear benefits of reusing the hard soil areas outweighed the possible, very minor negative effects.

• After separating the data into the two soil types, the data is broken into mine types. It might be tempting to simply group all of the targets together and say that the machine triggered a certain percentage of mines in one of the soil types. While this might be strictly true, it would also be misleading since it would only be true if an area were seeded with the exact proportions of those types of mines. While our trial used equal numbers of PMN, Type 72A and M14 mine types, a real minefield would probably not be so conveniently arranged.

• Within each soil and mine type grouping, the data is presented for each depth and for each pass of the machine.

With this arrangement, it is possible to make coherent, logical conclusions about the effectiveness of the roller against particular mines at particular depths, and about how many passes of the roller it takes to achieve these results.

3.2 Tire tests It is conceivable that the roller might fail to trigger a mine and that the vehicle tire might instead provide the necessary stimulus. Alternately, the tire might hit a mine during cornering or in other situations where the roller did not even touch it. Another possibility is that one of the large steel cage wheels might strike the mine instead of, or in addition to, the roller and/or the rubber tire. When these combinations (and there are probably more possibilities yet) are added to the 5-6 depths, two soil conditions and 3 mines, it quickly becomes apparent that it would take over 3000 additional tests to collect 20 data points in each condition. Since this was a test of the roller, and not a comprehensive test of the entire SDTT system, it was decided to test only a small subset of these conditions.

Each of the mine types was buried in hard and tilled soil in the same manner used for the roller tests. With the roller down to ensure proper weight distribution on the front and rear wheels, the rubber tire alone (no roller) was driven over the mine repeatedly. If the mine triggered, the statement could be made that it is possible for this type of mine to be triggered by the tire at this depth in this type of soil. The depth was increased and the test repeated until the mine could not be triggered after 8-10


attempts. This is admittedly an arbitrary number of tries and does not constitute proof of anything except that we were unable to trigger this mine with the tire in this particular test.

3.3 Footstep Tests

3.3.1 Footsteps Alone As noted above, a set of tests was done in which the mines were buried in the same way as for the roller, and were then walked on without first having been subjected to the roller. These trials were done in the same way as the tire tests; exhaustive testing with statistically meaningful data was not the goal. Again, this was a side issue and arguably not directly relevant to the effectiveness of the roller. It may, however, be useful in discussions about area or risk reduction by the roller. Area reduction and risk reduction issues are entirely outside the scope of this trial and this report, but the data is presented for others to consider.

3.3.2 Footsteps After Roller When the roller failed to trigger a target after all 8 passes, a human subject walked on the target up to 8 times to see if it would trigger. Conditions were actually rigged to increase the chances of triggering the mine. First, the human subject was chosen from one of three of the test team, each of whom weighed approximately 90kg. Second, the footfalls were arranged so that the point of the heel would strike as nearly as possible over the pressure plate of the mine. This ensured the full weight of the person concentrated on the smallest possible area, with as little bridging across the hole as could be managed. A third manipulation of conditions was the gait that was used. Rather than a simple, natural stride, the person would strike down with the point of the heel, and rock forward, hesitating on the way over before continuing onto the front of the foot and off the mine. Finally, in some early tests, where even 8 footsteps had failed to trigger the mine, the human subject stomped on the mine as hard as possible, again using the point of the heel so that bridging across the hole was minimized. This practice was discontinued, partly because it could unnecessarily damage the targets, but mostly because it hurt the person's knee too much.

As with the tire tests, it may not be strictly relevant to roller effectiveness whether a human footstep triggers a mine after the roller failed to do so, but the data may be of some value in area or risk reduction discussions. Again, the data is simply presented without judgement, and others may chose to use the data or not.

A reminder is in order at this point. The PMN and Type 72A targets were completely inert mechanical reproduction mine bodies, and the M14, although real, contained no detonator, and so was not hazardous in the footstep testing.


4. Test Results and Discussions

This section examines the data obtained during the trials and attempts to quantify the data in a meaningful way. One of the difficulties with trials such as these is the statistical nature of the data. In an ideal situation, a detailed statistical analysis would be based on hundreds or thousands of data points. In reality, this is not practical for machine tests such as this one.

Consider that these tests, which aimed for 15-20 targets in each condition, resulted in almost 700 targets and two weeks of trials with up to a dozen people preparing the site full time.. To improve the statistical nature of the data, one might try for 100 targets instead of 15-20, but this, of course means 3500-4600 targets and 10-13 weeks of trials. Taking machinery and personnel away from productive demining for 10-13 weeks, and absorbing the inevitable operating and maintenance loads along with personnel and materials costs is a much different situation than a two week trial; it is unlikely that most demining organizations would be willing or able to support the extended trial.

While perhaps not sufficient to keep a statistics purist happy, the volume of data collected in this 2 week trial is vastly larger than most other equipment trials. It is considered reasonable, representative, repeatable, and practical.

4.1 Roller Results As noted, the roller data is broken first in the hard and tilled soil conditions. For each soil condition the data is shown separately by mine type, and by depth and pass of the machine. For convenience, the data is shown in both tabular and graphical form.

4.1.1 Hard Soil

4.1.1.1 PMN in Hard Soil The data obtained for the PMN in hard soil is provided in Table 1 and Figure 15. This shows that the roller successfully triggered all targets down to 200mm depth of burial by the third pass of the machine. After the second pass 77 of the 79 targets had been triggered; only 2 targets at 200mm had been missed at that point.


Table 1. Effectiveness Against PMN in Hard Soil

DEPTH OF

BURIAL

QTY AT START

PERCENTAGE TRIGGERED AFTER PASS #

(mm) 1 2 3 4 5 6 7 8

0 16 88% 100% 100% 100% 100% 100% 100% 100%

25 16 100% 100% 100% 100% 100% 100% 100% 100%

50 16 100% 100% 100% 100% 100% 100% 100% 100%

100 16 94% 100% 100% 100% 100% 100% 100% 100%

200 15 53% 87% 100% 100% 100% 100% 100% 100%


Figure 15. Effectiveness Against PMN in Hard Soil


4.1.1.2 Type 72A in Hard Soil Table 2 and Figure 16 show the data for the Type72A in hard soil. It took 5 passes of the roller to trigger all 38 targets at 0mm and 25mm depths (19 at each depth). The data for 50mm shows all 8 passes being required to reach a peak of 94%, or 17 of the 18 targets. At 75mm a maximum of 95%, or 18 of the 19 targets triggered was achieved after 4 passes.

A significant drop in the effectiveness can be seen between 75mm and 100mm depth of burial. From a peak of 95% at 75mm, the numbers drop to only 10%, or 2 of the original 20 targets triggered at 100mm. The 20 targets at 150mm and the 20 at 200mm were unaffected by the roller.

Table 2. Effectiveness Against Type 72A in Hard Soil

DEPTH OF

BURIAL

QTY AT START


(mm) 1 2 3 4 5 6 7 8

0 19 89% 95% 95% 95% 100% 100% 100% 100%

25 19 84% 95% 95% 95% 100% 100% 100% 100%

50 18 56% 67% 67% 78% 78% 83% 89% 94%

75 19 68% 84% 89% 95% 95% 95% 95% 95%

100 20 5% 5% 5% 5% 5% 5% 10% 10%

150 20 0% 0% 0% 0% 0% 0% 0% 0%

200 20 0% 0% 0% 0% 0% 0% 0% 0%


Figure 16. Effectiveness Against Type 72A in Hard Soil


4.1.1.3 M14 In Hard Soil The effectiveness data against M14 mines in hard soil can be found in Table 3 and Figure 17. No M14 mines were triggered at 50mm or 100mm. Because of this, the 200mm depth of burial was not tested.

The M14, with its small, difficult to trigger pressure plate was triggered in 100% of the 20 cases at 0mm, but it took 7 passes to achieve this. Only 35 of the 39 mines at 25mm depth were triggered after a full 8 passes. The trend at this depth shows a steady increase from one pass to the next, and it is possible that additional passes might have continued to trigger more than35 mines at this depth.

Table 3. Effectiveness Against M14 in Hard Soil

DEPTH OF

BURIAL

QTY AT START


(mm) 1 2 3 4 5 6 7 8

0 20 80% 90% 95% 95% 95% 95% 100% 100%

25 39 41% 67% 77% 79% 82% 85% 87% 90%

50 20 0% 0% 0% 0% 0% 0% 0% 0%

100 20 0% 0% 0% 0% 0% 0% 0% 0%


Figure 17. Effectiveness Against M14 in Hard Soil


4.1.1.4 Hard Soil – Effects of Terrain Irregularities As noted above, testing under field conditions introduces the issue of terrain irregularities (soil unevenness, hole bridging, vegetation stubble, etc) and their effects. In the hard soil conditions there were a few targets which were singled out for special attention and are listed below in Table 4.

Table 4. Hard Soil – Terrain Irregularities

TRIAL # TARGET ID

DEPTH COMMENTS

(mm)

M14 Mines

2003-04-08-M14-8 M14-28 100 No trigger in 8 passes. Obvious bridging across hole.

PMN MRMs

2003-03-31-PMN-1 PMN-12 0 Triggered on pass 1. Right beside bamboo stubble.

2003-04-03-PMN-3 PMN-15 0 Triggered on pass 1. Right beside bamboo stubble.

2003-04-03-PMN-6 PMN-10 200 Triggered on pass 1. Possible bridging.

2003-04-03-PMN-6 PMN-28 200 Triggered on pass 1. Possible bridging.

Type 72A MRMs

2003-04-01-T72A-5 T72A-28 50 Triggered on pass 6. Beside bamboo roots/stubble.

2003-04-01-T72A-3 T72A-17 50 Triggered on pass 5. Terrain may have kept tractor wheel high and made roller not exert full weight on passes 1 and 2. Passes 3 and 4 appeared (visually) to have good ground contact.

2003-04-02-T72A-9 T72A-18 75 Triggered on pass 1. Bamboo stubble nearby.

2003-04-02-T72A-9 T72A-20 75 No trigger in 8 passes. Bamboo stubble (photo) Footsteps*8 = live. Stomp*1=triggered.

2003-04-01-T72A-5 T72A-1 100 No trigger in 8 passes. Footsteps *8=live. Stomp *1=triggered. Beside bamboo roots/stubble.

There are only a very few samples in Table 4, and so one must exercise great care in reading too much into the data, but it would appear that bamboo stubble and irregularities in the terrain may


sometimes have an effect, and sometimes not. It is clear, therefore, that the prudent course of action would be to identify the spots where these localized conditions might be present, to assume that they have not been processed properly by the roller, and then to check these spots by other methods. The data shown in Table 4 is included in the above tables.

4.1.1.5 Hard Soil – Anomalous Data There were a few targets which had to be removed from the statistical data tables for a number of reasons. These are listed below in Table 5 for the hard soil condition. All were malfunctions due to improper assembly, improper burial technique, or damage, and must be disregarded. These targets were not included in any of the previous tables or graphs.

Table 5. Hard Soil – Anomalous Data

TRIAL # TARGET ID

DEPTH COMMENTS

(mm)

2003-04-01-T72A-5 T72A-15 25 Deleted. Single pass only. Not triggered. Removed after pass #1 due to broken health wire. Wire appeared stretched – may have been pinched between roller disks and stretched.

2003-03-31-T72A-1 T72A-18 0 Deleted. Malfunction – improper assembly.



2003-04-02-T72A-9 T72A-10 75 Deleted. Malfunction – improperly mounted switch.

2003-04-03-PMN-6 PMN-21 200 Deleted. Malfunction – the target was not reset properly prior to burial, or was triggered during burial, before monitoring circuit was hooked up.

2003-04-08-M14-11 M14-5 25 Deleted. Malfunction – the mine was not armed properly prior to burial.

4.1.2 Tilled Soil Recall that the soil described as ‘tilled’ had been treated with a harrow and loosened to a depth of 100-150mm. Below that depth, the soil was still hard.


4.1.2.1 PMN in Tilled Soil Table 6 and Figure 18 show the data for the PMN buried in tilled soil. The figures show an impressive 100% trigger rate after a single pass at all tested depths down to 200mm.

With these results even at 200mm, four additional PMN targets were buried at 300mm and 4 at 350mm. The first pass triggered two at each of these depths, and the third pass triggered the other two at 300mm and one more at 350mm. There is insufficient data at these two depths to make meaningful predictions of performance, but we can conclude that at 300mm and even at 350mm the roller is able to trigger many PMNs.

Table 6. Effectiveness Against PMN in Tilled Soil

DEPTH OF

BURIAL

QTY AT START


(mm) 1 2 3 4 5 6 7 8

0 13 100% 100% 100% 100% 100% 100% 100% 100%

25 19 100% 100% 100% 100% 100% 100% 100% 100%

50 19 100% 100% 100% 100% 100% 100% 100% 100%

100 16 100% 100% 100% 100% 100% 100% 100% 100%

200 16 100% 100% 100% 100% 100% 100% 100% 100%

300 4 50% 50% 100% 100% 100% 100% 100% 100%

350 4 50% 50% 75% 75% 75% 75% 75% 75%


Figure 18. Effectiveness Against PMN in Tilled Soil


4.1.2.2 Type 72A in Tilled Soil It took 1, 3 and 4 passes to trigger all 20 Type 72A mechanical reproduction mine bodies at 0mm, 25mm, and 50mm, respectively. At 100mm, 23 of the 24 targets had been triggered following the sixth pass.

At depths greater than 100mm the effectiveness drops off significantly. This is not a surprise, but there is a curious reversal from 100mm to 125mm to 150mm. The overall results drop from 96% to 35% and then come back up to 50% before finally dropping to only 8% at the 200mm depth. The difference between 35% and 50% amounts to only 3 targets of the 20 at each depth, so the reversal may not be statistically significant.

Table 7. Effectiveness Against Type 72A in Tilled Soil

DEPTH OF

BURIAL

QTY AT START


(mm) 1 2 3 4 5 6 7 8

0 20 100% 100% 100% 100% 100% 100% 100% 100%

25 20 90% 95% 100% 100% 100% 100% 100% 100%

50 20 90% 95% 95% 100% 100% 100% 100% 100%

100 24 71% 79% 92% 92% 92% 96% 96% 96%

125 20 20% 25% 25% 30% 35% 35% 35% 35%

150 20 40% 50% 50% 50% 50% 50% 50% 50%

200 13 8% 8% 8% 8% 8% 8% 8% 8%


Figure 19. Effectiveness Against Type 72A in Tilled Soil


4.1.2.3 M14 In Tilled Soil The effectiveness of the roller against M14 mines in tilled soil is shown in Table 8 and Figure 20. At 0mm depth, 16 of the 17 mines were triggered immediately on the first pass but it took all 8 passes to finally trigger the remaining mine. It is notable that this mine was visually inspected after pass 2, 3, 4, 5, and 6 to ensure that it was, in fact, live, and not a malfunction. There were no obvious ground irregularities or vegetation obstacles that would explain the lone holdout.

At the other end of the depth spectrum, the effectiveness at 75mm dropped significantly, reaching a peak of only 20% after 4 passes. At 100mm, the peak of just 10% was reached on the second pass.

Whereas the numbers at 0mm, 75mm and 100mm quickly reached plateaus, the effectiveness at 25mm and 50mm tended to climb gradually. At 25mm, the numbers climbed through the first six passes, and at 50mm the number of triggered mines continued to rise through all 8 passes, eventually peaking at 85%, or 17 of the 20 mines at that depth. It is possible that additional passes might have increased the number of triggered mines.

Table 8. Effectiveness Against M14 Mines in Tilled Soil

DEPTH OF

BURIAL

QTY AT START


(mm) 1 2 3 4 5 6 7 8

0 17 94% 94% 94% 94% 94% 94% 94% 100%

25 40 28% 45% 65% 85% 88% 90% 90% 90%

50 39 28% 56% 69% 74% 74% 77% 79% 85%

75 20 0% 0% 5% 20% 20% 20% 20% 20%

100 20 5% 10% 10% 10% 10% 10% 10% 10%


Figure 20. Effectiveness Against M14 Mine in Tilled Soil


4.1.2.4 Tilled Soil – Effects of Terrain Irregularities As with the hard soil, terrain irregularities can be an issue when testing under field conditions. The few targets in tilled soil which are of note are listed below in Table 9. Again, there are only a very few samples, and so one must exercise great care in reading too much into this information. Again it would appear that these irregularities may sometimes have an effect, and sometimes not, and so the prudent course of action would be to identify the spots where these localized conditions might be present, to assume that they have not been processed properly by the roller, and then to check these spots by other methods. The targets listed in Table 9 are included in the previous tables and graphs but have also been listed here as items of interest.

Table 9. Tilled Soil – Terrain Irregularities

TRIAL # TARGET ID

DEPTH COMMENTS

(mm)

M14

2003-04-07-M14-4 M14-12 25 50mm soil on top after trial (from bow wave).

2003-04-07-M14-4 M14-16 25 Big bow ware on pass 5. 80-90mm soil on top after trial.

2003-04-07-M14-5 M14-28 75 60mm compacted soil on top after roller (from bow wave). Footsteps *1=triggered

Type 72A

2003-04-01-T72A-4 T72A-4 150 No trigger in 8 passes. Soil possibly damp.

2003-04-01-T72A-4 T72A-3 150 No trigger in 8 passes. Soil possibly damp.

2003-03-31-T72A-2 T72A-8 200 No trigger in 8 passes. 30-40mm extra soil from bow wave. Footsteps *8=live.

2003-03-31-T72A-2 T72A-13 200 No trigger in 8 passes. 30-40mm extra soil from bow wave. Footsteps *8=live.

2003-04-01-T72A-7 T72A-2 200 No trigger in 8 passes. Extra soil from bow wave pass 1.

2003-04-01-T72A-7 T72A-14 200 Triggered on pass 1. Extra soil from bow wave pass 1.

2003-04-01-T72A-7 T72A-21 200 No trigger in 8 passes. Extra soil from bow wave pass 1.


It is interesting to compare targets T72A-2, T72A-14 and T72A-21 from trial 2003-04-01-T72A-7. All were at 200mm and all were seen to have additional soil deposited by the bow wave on the first pass. One of these was triggered on the first pass, while the other two were unaffected through all 8 passes. This shows that the small amount of soil moved by the bow wave is probably inconsequential. It also illustrates possible variability in results when all conditions appear to be identical.

4.1.2.5 Tilled Soil – Anomalous Data As noted above, there were a few data targets which had to be removed from the statistical data tables. These are listed in Table 10 for the tilled soil condition. None of these targets provided useable data for the roller, and none were included in the previous tables or graphs.

Table 10. Tilled Soil – Anomalous Data

TRIAL # TARGET ID

DEPTH COMMENTS

(mm)

2003-04-07-M14-7 M14-5 0 Deleted. Triggered on first pass after both a roller strike and a tire strike. Unknown which strike triggered the mine.

2003-04-07-M14-7 M14-25 0 Deleted. Triggered on first pass after both a roller strike and a tire strike. Unknown which strike triggered the mine.

2003-03-31-PMN-2 PMN-5 0 Deleted. Malfunction – damaged switch.

2003-03-31-PMN-2 PMN-23 25 Deleted. Malfunction – damaged switch.

2003-04-01-T72A-7 T72A-18 200 Deleted. Malfunction – damaged power supply wire, possibly caused by soil movement of bow wave on first pass.



2003-04-07-M14-6 M14-25 50 Deleted. Malfunction – improperly mounted switch.

2003-04-07-M14-7 M14-9 0 Deleted. Malfunction – broken solder joint on switch.


4.2 Tire Results While the trial program was designed to test the effectiveness of the SDTT roller, it was suggested that it might be useful to examine the effects of a tire passing over the mines. It was determined that it would be possible to include the effect of one of the SDTT rubber tires, without significantly affecting the time, cost, or complexity of the program. It was not deemed practical to include the combination of roller and tire when the mine had not been triggered by the roller. Further, the geometry of the SDTT open, steel cage wheels would have made testing extremely difficult since it would be hard to ensure contact between the steel cleats and the mine location.

The intent was not to produce statistically significant data. Rather, the intent was to determine whether it was possible that a tire strike would be able to trigger the mines under certain conditions. A single successful trigger was enough to say “yes, it is possible.” It was not enough to predict the probability of triggering mines in this way. If 8 (or sometimes even more) passes of the tire were not able to trigger the mine, all that could be said was that the test was inconclusive; one could not be absolutely certain that triggering was impossible, but we had not been able to demonstrate that it was possible. Hence, ‘not proven’ was used in Table 11 and Table 12.

Table 11. Tire Strike Tests – Hard Soil

TYPE SOIL DEPTH CAN BE TRIGGERED BY RUBBER TIRE TREAD STRIKE

PMN Hard 100, 200 Yes

Type 72A Hard 25, 50, 100 Yes

M14 Hard 0, 50 Yes

M14 Hard 25 Not proven – see note 2

1. Note that ‘Yes’ simply indicates that at least one attempt to trigger the mine was successful. It does not indicate that it will always be successful. Likewise, ‘Not proven’ indicates only that we were unable to trigger the mine in up to 8 tests. It may indeed be possible to trigger the mine under these conditions but our data could not prove this either way.

2. The one example in this condition was subjected to 10 different tire strikes, all of which were carcass strikes rather than tread strikes. This data point is therefore inconclusive, but does point to the difficulty in triggering via tire carcass strikes.


Table 12. Tire Strike Tests- Tilled Soil

TYPE SOIL DEPTH CAN BE TRIGGERED BY RUBBER TIRE TREAD STRIKE

PMN Tilled All depths Not tested

Type 72A Tilled 100, 150 Yes

M14 Tilled 0, 25, 50, 100 Yes

M14 Tilled 150 Not proven

Note that ‘Yes’ simply indicates that at least one attempt to trigger the mine was successful. It does not indicate that it will always be successful. Likewise, ‘Not proven’ indicates only that we were unable to trigger the mine in up to 8 tests. It may indeed be possible to trigger the mine under these conditions but our data could not prove this either way.

4.3 Footstep Results It was suggested that it might be useful if there was something against which the roller performance could be compared. A possible comparison would be to compare the ability of the roller in triggering mines to the effect of a human footstep in triggering those same mines. It might also be useful to examine the effect of a human footstep on a mine which had been repeatedly processed by the roller without having been triggered. These two conditions were included in the trial program since they did not significantly affect the time, cost, or complexity of the program.

Again, the intent was not to produce statistically meaningful data, but simply to determine whether it was possible for footsteps to trigger the mines in specific conditions. As with the tire strikes, a single successful trigger was only enough to say “yes, it is possible.” If 8 or more footsteps were not able to trigger the mine, all that could be said was that the test was inconclusive; one could not be absolutely certain that triggering was impossible, but we had not been able to demonstrate that it was possible. Hence, ‘not proven’ was used in the tables.

In all, three different test subjects were used for the footstep tests. All three were approximately the same height and mass. Heights varied between approximately 1.78m and 1.88m, and mass ranged between 82kg and 90kg. Initially the footsteps were made as naturally and smoothly as possible, with the heel impacting the middle of the hole in which the mine had been buried. When it became apparent that a particular mine was not reacting to the footsteps, the test subject would modify the footstep pattern to ensure that the point of the heel impacted the ground a little more firmly, and the stride would be slowly rocked over the mine in an exaggerated attempt to apply as much load as possible.

In every case it was possible that the test subject might have missed stepping exactly on the centre of the mine. This possibility increased as the depth of the mine


increased. In the footstep-after-roller tests in tilled soil, the problem was even more acute because the roller tended to create a soil bow-wave which could move the surface layer of soil 100mm or more from its original position, making it very difficult to determine exactly where the heel strike should occur. It is largely for this reason that the results below are not summarized by the number of steps needed to trigger the mine in question. Another reason is the variability in loading; slight changes in stride might make significant differences in the loading experienced by a mine, and so it would be misleading to state that it takes a particular number of steps to trigger it.

As with the roller trials, all of the footstep trials used up to 8 heel strikes, coming from 8 different directions. The was done to try to minimize errors in position, soil bridging or other possible directional effects that might be present.

The observant reader will note that the data in Annex A includes references to ‘jumps’ and ‘stomps.’ In some of the tests where the footsteps had not triggered the mine, the test subject attempted to trigger the mine by jumping or stomping on it. Not only was this very hard on the person’s knees, but it was also very unrealistic, and a completely unreasonable test condition. Providing that a mine is operational, it will always be possible to trigger it if enough force is applied. Indeed, in a few cases, the test subject abandoned the stomping, only to have a particularly zealous TMAC team member stomp another 20 or 30 times and eventually succeed in triggering the mine. It may be possible, but it may also be completely absurd. Jumping or stomping on mines is clearly absurd. The ‘stomp’ data therefore has been left in Annex A but is not analyzed in any way.

4.3.1 Footsteps Alone As noted above, the footstep tests are not directly relevant to the effectiveness of the roller, but may be useful to others as supporting data. As with the roller tests, the raw data is given in Annex A. The footstep data summarized below in Table 13 and Table 14 shows the net effect of footsteps on buried mines, without the use of the roller.

Table 13. Footstep Tests in Hard Soil– No Roller

TYPE SOIL DEPTH CAN BE TRIGGERED WITHIN 8

FOOTSTEPS

PMN Hard All depths Not tested

Type 72A Hard 100 Yes

Type 72A Hard 200 Not proven – 4 attempts

M14 Hard All depths Not tested

Note that ‘Yes’ simply indicates that at least one attempt to trigger the mine was successful. It does not indicate that it will always be successful. Likewise, ‘Not proven’ indicates only that we were unable to trigger the mine in 3 or 4 attempts of 8-10 footsteps each. It may indeed be possible to trigger the mine under these conditions but our data could not prove this either way.


Table 14. Footstep Tests in Tilled Soil – No Roller


FOOTSTEPS

PMN Tilled 100, 150, 200, 250 Yes

Type 72A Tilled 0, 25, 50, 100, 125 Yes

Type 72A Tilled 150 Not proven – 3 attempts

M14 Tilled 0, 25, 50, 75 Yes

M14 Tilled 100 Not proven – 3 attempts

Note that ‘Yes’ simply indicates that at least one attempt to trigger the mine was successful. It does not indicate that it will always be successful. Likewise, ‘Not proven’ indicates only that we were unable to trigger the mine in 3 or 4 attempts of 8-10 footsteps each. It may indeed be possible to trigger the mine under these conditions but our data could not prove this either way.

Recall that a single successful trigger was enough only to say “yes, it is possible.” In cases where 8, or sometimes even 10, footsteps were not able to trigger the mine, the same test was repeated 3 or 4 times. If, after 3 or 4 such attempts the mine was still not triggered, one still could not be absolutely certain that triggering was impossible, so ‘not proven’ is shown in the table.

4.3.2 Footsteps After Roller After the roller had processed an area, mines which had not been triggered were subjected to human footsteps. As described above, the intent was only to discover whether it was possible to trigger the mines by foot after the roller had passed. The raw data is included in Annex A for the interested reader to peruse at will. Table 15 and Table 16 summarize the data for hard and tilled soil respectively.


Table 15. Footstep Tests in Hard Soil – After Roller


FOOTSTEPS?

PMN Hard 0-200mm No tests done – all triggered by roller


Type 72A Hard 75 Not proven – see note 2


Type 72A Hard 150, 200 Not proven

M14 Hard 25, 50 Yes

M14 Hard All other depths Not tested

1. Note that ‘Yes’ simply indicates that at least one attempt to trigger the mine was successful. It does not indicate that it will always be successful. Likewise, ‘Not proven’ indicates only that we were unable to trigger the mine within 8 attempts. It may indeed be possible to trigger the mine under these conditions but our data could not prove this either way.

2. The Type 72A at 75mm depth was in the midst of bamboo stubble/roots. This was the only sample at this depth and may therefore not be representative.


Table 16. Footstep Tests in Tilled Soil – After Roller


FOOTSTEPS?

PMN Tilled 0-300mm No tests done – all triggered by roller

PMN Tilled 350mm Not tested

Type 72A Tilled 100 Not proven

Type 72A Tilled 125 Yes

Type 72A Tilled 150, 200 Not proven


M14 Tilled 50, 75 Yes


Note that ‘Yes’ simply indicates that at least one attempt to trigger the mine was successful. It does not indicate that it will always be successful. Likewise, ‘Not proven’ indicates only that we were unable to trigger the mine within 8 attempts. It may indeed be possible to trigger the mine under these conditions but our data could not prove this either way.


5. Conclusions

Conclusions regarding the effectiveness of the roller must be tempered by several factors.

• Despite collecting a large number of data points compared with most other machine test programs, only 16-40 data points for any given condition are available. A thorough statistical analysis might reveal that differences of 5-10% may not be statistically significant.

• Only three mine types were analyzed, and only in two environmental (soil/vegetation) conditions available at the test site in Thailand. This is, at least, highly representative of real minefield soil and vegetation conditions at this location, but care must be taken when applying the data to other locations. Due to an unfortunate schedule conflict with some of the trial team, the equipment intended for analyzing soil hardness was not available. The soil could therefore only be described in qualitative terms.

• The targets had to be placed in fresh holes, and the soil could only be minimally packed over two of the mine types. It could not be packed at all over the third type. Unless the area were freshly mined, the soil in a real minefield would have gradually become more uniform and consistent around and above the mines. This is a simple restriction that all such test programs will be under. The effects of this were minimized to the extent possible by (i) hand-packing the soil over the Type 72A and M14 targets, and (ii) making the holes as small as possible to decrease the ‘soft-soil’ effects around the mine.

It is always tempting to view data such as was collected during these trials, with an eye to saying that the machine is, or is not, good for certain uses. In some cases this determination can be made, especially if the manufacturer makes specific performance claims. In the case of the roller, the matter is a little less clear. As far as the test team is aware, there are no specific claims about the effectiveness of the roller against particular mines at particular depths, in particular soil conditions. Further, the roller is employed, not on its own, but in combination with other SDTT tools. Finally, the roller may be proposed in its own right for mine clearance or as one part of a system for area reduction or risk reduction. The factors which determine the value of the machine will likely be very different for each of these scenarios, and will also be different for each demining organization, and for different locations which may have different end-use requirements.

As a results, this report is restricted to presenting the results without attempting to make definitive evaluations about the value of the machine. It is hoped that the readers (end users in particular) can make effective use of this information in drawing their own conclusions.

5.1 Roller Effectiveness No single number can be used to summarize the roller effectiveness. The effectiveness is defined by the combination of depth, soil condition, mine type, and number of


passes of the roller over the mine. The raw data is provided in Annex A, and is summarized, tabulated and plotted above in Section 4.

5.1.1 Effectiveness in hard soil In the hard soil the roller was able to trigger the PMN very effectively down to 200mm in up to three passes. It is not surprising that the PMN was triggered with some ease since it has a very large pressure plate and is easily triggered by the application of a load anywhere on the pressure plate.

The M14 was much more difficult for the roller to trigger. None of the M14 mines buried more than 25mm were triggered. It took 7 passes to trigger all of the M14 mines buried flush with the ground surface. Less than half of those buried at 25mm were triggered on the first pass. After a full 8 passes 90% had been triggered. The M14 mine has a very small pressure plate which is much more difficult to trigger than the PMN.

Between the easily triggered PMN and the more difficult M14 lies the Type 72A. The Type 72A pressure plate is slightly larger than that of the M14, and it did not exhibit the triggering difficulty exhibited by the M14. Predictably then, the effectiveness of the roller against the Type 72A fell between the PMN and the M14. After 5 passes, every Type 72A had been triggered at 0mm and 25mm depths. At 50mm and 75mm, the effectiveness reached maximums of 94% and 95% triggered. There was a sharp drop-off between 75mm and 100mm, with only 1 of 20 targets being triggered in the first 6 passes at 100mm. Not one Type 72A was triggered at either 150mm or 200mm.

5.1.2 Effectiveness in tilled soil As noted, the tilled soil is representative of conditions after the SDTT harrow has been used, or where active cropland has been mined recently. In this soil condition a mine buried at 100mm may only have 50-75mm of soil over it after the roller has passed, simply due to the compaction of the loose soil. This is seen in the consistent ability of the roller to trigger mines more deeply buried in the tilled soil than in the hard soil.

There can also be a bow-wave, or bulldozer effect in which the loose soil near the surface is pushed around by the roller. This may strip soil off a mine, or it may pile more soil on top of it.

In the tilled soil, the roller triggered every PMN down to 200mm on the first pass. While it was also able to trigger all four targets at 300mm and 3 of 4 targets at 350mm in three passes, these two conditions should not be viewed as statistically significant due to the small number of samples. Clearly, the roller is very effective in triggering the PMN model at all reasonable depths.

By the end of the fourth pass, every Type 72A down to 50mm had been triggered along with 22 of the 24 at 100mm. One more pass triggered one additional target at 100mm. A sharp drop in the numbers occurs between


100mm and 125mm. The best that could be achieved below 100mm was 35% at 125mm, 50% at 150mm, and 8% at 200mm.

One M14 mine at 0mm depth stubbornly resisted triggering until the 8th and final pass of the roller. All of the others at this depth were triggered on the first pass. The trends at 25mm and 50mm were very much alike, starting with only 28% on the first pass, climbing to about 50% on the second, 65-70% on the third, and so on. At 25mm the trend peaked at 90% on the sixth pass, while at 50mm, the numbers climbed through all 8 passes to a maximum of 85%. The numbers plummeted to only 20% and 10% at 75mm and 100mm respectively.

5.1.3 Overall Roller Effectiveness Within the limitations of the trial, the roller was shown to be very effective against the PMN at all depths to at least 200mm. The M14 and Type72 were much more difficult to trigger under all conditions. Taking greater-than-90% as an arbitrary benchmark, the M14 was only triggered reliably at 0mm depth in hard soil, and down to 25mm in tilled soil. Over 90% of the Type 72A targets were triggered in hard soil to 75mm deep, and in tilled soil to 100mm deep.

It cannot be concluded that the roller would be effective as a mine clearing device in its own right except in very unusual circumstance. On the other hand, the SDTT segmented roller may be a very useful part of an overall systems approach to demining. As part of a larger operating procedure the roller may also be useful in area reduction or risk reduction. Its utility in such a situation will depend very much on how the roller is used, how many times it is applied over the same piece of ground, what other, non-roller techniques are used, etc. This evaluation is well beyond the scope of this report, but the results of this trial may be useful in defining or refining an overall, multi-pronged approach to the problem.

5.2 Tire Strikes Tire strikes (without passage of the roller) were observed to trigger mines to the depths indicated below. As noted for the foot strikes, this data indicates only that at least one such observation was made, and no claims are made about statistical significance or proof. Again, the tire test data is not strictly relevant to the effectiveness of the SDTT segmented roller in triggering mines, and is presented without judgement for the reader to draw his or her own conclusions, if any.

In all cases the tire tread had to strike the mine in order to trigger it. No mines were triggered by tire carcass strikes in these tests.

In hard soil, the PMN was triggered at 100mm and 200mm. The Type 72A was triggered at 25mm, 50mm, and 100mm, and the M14 at 0mm and 50mm. In tilled soil, the Type 72A was observed to trigger at 100mm and 150mm, while the M14 was triggered at 0mm, 25mm, 50mm, and 100mm. There were no tests done against the PMN in tilled soil.


Recall that this data means that a single case of triggering was accepted as proof that a tire strike could trigger the mine under the specified conditions, and not that a tire strike would trigger the mine.

5.3 Foot Strikes Alone Footsteps alone were found to trigger Type 72A mines down to 100mm in hard soil. This does not imply that footsteps will always do so; it only indicates that it was demonstrated to be possible for this to happen. At 200mm, there was no evidence of triggering, but again, this does not indicate that footsteps are unable to trigger the mine under these conditions. The PMN and M14 were not used in hard soil footstep tests.

It was shown that footsteps were able to trigger the PMN down to 250mm, the Type 72A down to 150mm and the M14 down to 100mm in tilled soil. Again, this only showed triggering to be possible. Footsteps against the Type 72A at 150mm and the M14 at 100mm were not shown to be able to trigger the mines, but again, this does not indicate that the footsteps are actually unable to do so.

5.4 Foot Strikes After The Roller In the hard soil, footsteps against the Type 72A at 50mm and 100mm were able to trigger the mine at least some of the time. The one example at 75mm was in the middle of a bamboo root/stubble cluster, and the results are probably not representative. At 150mm and 200mm footsteps could not be proven able to trigger the Type 72A. The M14 was only tested at 25mm and 50mm in hard soil, and in both cases footsteps were able to trigger the mines in some cases.

In tilled soil, following 8 passes of the roller, footsteps were observed to trigger the Type 72Aat 125mm and the M14 at 50mm and 75mm. Tests against the Type 72A at 100mm, 150mm and 200mm, and against the M14 at 25mm and 100mm were inconclusive; the footsteps did not trigger these mines in the tests conducted, but other results are certainly possible.

Because the roller was so effective in triggering PMN mines in both hard and tilled soil, there was no opportunity to test footsteps after the roller.


6. Recommendations

The obvious question that arises from a trial such as this, is whether heavier roller disks would improve the performance. There was no practical way to evaluate this in the current trial, but it does bear some consideration. Obviously a limit will be reached beyond which the SDTT cannot support additional weight. Manoeuvrability might suffer with a heavier roller. Increasing the weight of the disks implies a change in disk dimensions which might have adverse effects beyond the simple weight consideration. A larger diameter or wider disk might not follow terrain irregularities as well. A larger disk might also have a larger footprint that spreads the weight out and nullifies the effect of the weight increase, especially for more deeply buried mines (where the weight increase is targeted). In addition, the current segmented roller is a model of simplicity. It is difficult to imagine a change (other than a simple weight increase) that could be achieved without increasing the complexity of the machine.

The trial team agreed that research into the effects of heavier roller segments, or ways to increase the ground loading of the existing segments would be beneficial. It is not known whether the effectiveness could be improved significantly before the load limits or manoeuvrability of the machine are compromised. It is also not known whether the inevitable increases in cost and complexity would be justified by the possible increased effectiveness.

A research program that investigates roller disk geometry, weight and subsurface ground pressure is recommended. This should focus on practical, achievable solutions that might yield immediate improvements to field equipment. Depending on the results of such a study, it may be useful to repeat a part of the current trial program using modified rollers.


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Annex A – Raw Trial Data

Notes:

In the data tables which follow, ‘GGC’ is simply a convenient placeholder noting the anomalous data which needs to be removed from the data tables and treated separately.


Annex A - Test Data Recording Sheets


Annex A: Test Data Recording Sheets


Test PMN-9 not used



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Annex B – Trial Photographs

Notes:

The photographs in this annex document the typical trial conditions, procedures, and effects, along with occasional peculiar situations.


PMN mechanical Reproduction Mines modified to use EDRIFT

EDRIFT Monitoring Circuits

EDRIFT indicator showing ‘triggered’ target

Typical Test Layout



Marking M14 Mine as ‘used’ Typical test area before vegetation mowing

Typical test area before vegetation mowing

Typical test area after vegetation mowing (‘hard’ soil condition)



Harrow used to create ‘tilled’ soil condition from ‘hard’ soil condition

Harrow used to create ‘tilled’ soil condition from ‘hard’ soil condition

‘Tilled’ soil after vegetation mowing and harrow application

‘Tilled’ soil after vegetation mowing and harrow application



Laying out test lane in ‘hard’ soil Groups of 4 target location in ‘hard’ soil test lane

Checking 100mm depth of burial for Type 72A MRM body in ‘hard’ soil

Checking 200mm depth of burial for Type 72A MRM body in ‘hard’ soil



Type 72A MRM body and EDRIFT cable ready for burial

Group of four Type 72A MRM bodies and EDRIFT cables ready for burial

Preparing PMN MRM bodies and EDRIFT cables

Marking target locations with lime



Starting test run on long axis of test lane Guiding machine along long axis of test lane

Checking EDRIFT indicators after roller pass

Machine pass crosswise over test area



Preparing test lane in ‘tilled’ soil Machine run along long axis of test lane

Roller pass over targets in ‘tilled’ soil Typical ‘tilled’ soil condition after roller pass



Typical ‘bow wave’ formation in early passes over ‘tilled’ soil

Typical ‘bow wave’ formation in early passes over ‘tilled’ soil

Roller Segments handling uneven ground Roller segments barely able to cope with uneven ground



Roller unable to maintain ground contact over uneven ground



Bamboo root/stubble interferes with roller effectiveness



SDTT rubber tire used in tire strike tests Tire strike test

Partial strike by tire tread – see pen for tread location

Miss by tire treads – tread locations highlighted by red lines



Direct hit by tire tread Cage wheel not used in tire strike tests

Footstep/heel-strike test example Footstep/heel-strike test example



Footstep/heel-strike test example SDTT Trial Team (week 2)

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Annex C – Equipment Supplementary Data

In addition to the data that was collected above in Annex A and B, a few supplementary pieces of information were collected which may be of some value in interpreting the trial results. This additional information is not actually used in the analysis contained in this report, but is provided as a courtesy to the reader who might have a use for it. All dimensions are in centimetres, and all are approximate.

The first sketch shows the approximate footprint of the SDTT rubber tire in both hard soil (the narrow footprint) and tilled soil (the wider footprint). As the actual footprint will depend greatly on the soil condition, tire pressure, vehicle loading, tire wear, and possibly many other factors, the following values are only approximate. It bears repeating that in both hard and tilled soil, contact between the tire treads and a mine had a chance of triggering the mine. Contact between the tire carcass and a mine stood very little chance of triggering the mine even at shallow depths. Further, there is nothing to suggest that the load imparted along the tire centreline is similar to the load imparted close to the tire edge.

In both hard and tilled soil conditions, tread contact makes up only about 25-30% of the footprint.

The second sketch shows the overall dimensions of the segmented roller mechanism. The loose fit between the shaft and the roller segments allows approximately 10cm of vertical displacement to follow ground irregularities.


Annex C – Tread pattern from one rotation of the tire (approximate)


Annex C – Roller dimensions (approximate)


List of symbols/abbreviations/acronyms/initialisms

CCMAT Canadian Centre for Mine Action Technologies

cm Centimetres

DRDC Defence R&D Canada

EDRIFT Electronic Detonator Replacement and Interrogation of Fuze Triggering

HDPO Humanitarian Demining Program Office

HMAU1 Humanitarian Mine Action Unit #1

mm Millimetres

SDTT Survivable Demining Tractor and Tools

TMAC Thailand Mine Action Centre


Glossary

Technical term Explanation of term

Minefield Strictly speaking, a minefield is a defined area with specific boundaries containing landmines. This is in contrast to a ‘mined area’ which may not have clearly defined boundaries. For convenience, this document uses the term ‘minefield’ to refer to any piece of land which is suspected of containing one or more landmines.

Depth of Burial Depth as measured from the ground surface down to the top of the mine

Bow wave Soil pushed ahead of the roller

Tread(s) The tread or lug portion of the rubber tire which provides grip

Carcass The smooth casing portion of the rubber tire between the treads.

UNCLASSIFIED SECURITY CLASSIFICATION OF FORM (highest classification of Title, Abstract, Keywords)

DOCUMENT CONTROL DATA (Security classification of title, body of abstract and indexing annotation must be entered when the overall document is classified)

1. ORIGINATOR (the name and address of the organization preparing the document. Organizations for who the document was prepared, e.g. Establishment sponsoring a contractor's report, or tasking agency, are entered in Section 8.)

Defence R&D Canada – Suffield PO Box 4000, Station Main Medicine Hat, Alberta T1A8K6

2. SECURITY CLASSIFICATION (overall security classification of the document, including special

warning terms if applicable) Unclassified

3. TITLE (the complete document title as indicated on the title page. Its classification should be indicated by the appropriate abbreviation (S, C or U) in parentheses after the title).

Field Testing of the SDTT Segmented Roller (U)

4. AUTHORS (Last name, first name, middle initial. If military, show rank, e.g. Doe, Maj. John E.)

Coley, Geoff, G.

5. DATE OF PUBLICATION (month and year of publication of document)

October 2003

6a. NO. OF PAGES (total containing information, include Annexes, Appendices, etc)

131

6b. NO. OF REFS (total cited in document)

0

7. DESCRIPTIVE NOTES (the category of the document, e.g. technical report, technical note or memorandum. If appropriate, enter the type of report, e.g. interim, progress, summary, annual or final. Give the inclusive dates when a specific reporting period is covered.)

Technical Report

8. SPONSORING ACTIVITY (the name of the department project office or laboratory sponsoring the research and development. Include the address.)

Canadian Centre for Mine Action Technologies

9a. PROJECT OR GRANT NO. (If appropriate, the applicable research and development project or grant number under which the document was written. Please specify whether project or grant.)

9b. CONTRACT NO. (If appropriate, the applicable number under which the document was written.)

10a. ORIGINATOR'S DOCUMENT NUMBER (the official document number by which the document is identified by the originating activity. This number must be unique to this document.)

DRDC Suffield TR 2003-107

10b. OTHER DOCUMENT NOs. (Any other numbers which may be assigned this document either by the originator or by the sponsor.)

11. DOCUMENT AVAILABILITY (any limitations on further dissemination of the document, other than those imposed by security classification) ( x ) Unlimited distribution ( ) Distribution limited to defence departments and defence contractors; further distribution only as approved ( ) Distribution limited to defence departments and Canadian defence contractors; further distribution only as approved ( ) Distribution limited to government departments and agencies; further distribution only as approved ( ) Distribution limited to defence departments; further distribution only as approved ( ) Other (please specify):

12. DOCUMENT ANNOUNCEMENT (any limitation to the bibliographic announcement of this document. This will normally corresponded to the Document Availability (11). However, where further distribution (beyond the audience specified in 11) is possible, a wider announcement audience may be selected).

Unlimited

UNCLASSIFIED SECURITY CLASSIFICATION OF FORM


13. ABSTRACT (a brief and factual summary of the document. It may also appear elsewhere in the body of the document itself. It is highly desirable that the abstract of classified documents be unclassified. Each paragraph of the abstract shall begin with an indication of the security classification of the information in the paragraph (unless the document itself is unclassified) represented as (S), (C) or (U). It is not necessary to include here abstracts in both official languages unless the text is bilingual).

In March and April 2003, the Canadian Centre for Mine Action Technologies (CCMAT), the U.S. Humanitarian Demining Office, and the Thailand Mine Action Centre undertook a cooperative trial of the Pearson Survivable Demining Tractor and Tools with its segmented roller attachment. This trial evaluated the effectiveness of the roller attachment in triggering three different antipersonnel landmines at depths ranging from 0mm to 200mm. In one case the depth was actually extended to 350mm. Two different soil conditions were used to evaluate (i) hard, recently de-brushed conditions, and (ii) freshly tilled or loosened soil. This project makes up a part of the ongoing CCMAT efforts at test and evaluation of mechanical equipment for demining operations.

14. KEYWORDS, DESCRIPTORS or IDENTIFIERS (technically meaningful terms or short phrases that characterize a document and could be helpful in cataloguing the document. They should be selected so that no security classification is required. Identifies, such as equipment model designation, trade name, military project code name, geographic location may also be included. If possible keywords should be selected from a published thesaurus, e.g. Thesaurus of Engineering and Scientific Terms (TEST) and that thesaurus-identified. If it is not possible to select indexing terms which are Unclassified, the classification of each should be indicated as with the title.)

Canadian Centre for Mine Action Technologies CCMAT Mechanical Assistance Equipment Mechanically Assisted Clearance Equipment Test and Evaluation Mechanical Reproduction Mine Anti personnel landmine Humanitarian demining Neutralization Pearson SDTT Survivable Demining Tractor and Tools TMAC Thailand Mine Action Center


field testing of the sdtt segmented rollerfield testing of the sdtt segmented roller. drdc suffield...

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