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United Nations Demining Programme
Mozambique

Subject: MECHANICAL MINE CLEARANCE TRIAL - FINAL REPORT
Date: 30 May 1996                                File: 1003/13

Introduction

1.     The Krohn Demining System was introduced to Mozambique in August 1995. Development of procedures and machines to the environment took place with support from the UN ADP. These develpments led to a field trial being conducted at Sabie on 6 - 7 May 1996. The trial featured 264 live mines placed in a prepared area that was then cleared by machine. The aim of the trial was to provide a quantifiable record of the performance of the Krohn Deming System.

Test Minefield

2.     Location. The trial took place 2km south of Sabie town in the district of Moamba, Maputo Province, 120km north of Maputo city.

3.     Ground. The test area was on level ground with light, dry, stone free soil covered by thin patches of grass. The area was formally agricultural land which had been fallow for a number of years. A photographs of the test site are attached at Annex A.

4.      Mines. The following mines were obtained through the Mozambican Ministry of Defence and were used for the trial.

It was hoped to use a greater range of mines reflecting all types found throughout Mozambique but they were not available. However, the mines supplied are those most commonly found in Maputo Province.
5.        Test Area Layout. The test area was 185 metres long and 10 metres wide. It consisted of 12 panels (10 m x 10 m) each separated by a buffer zone (5 m x 10 m). Twenty two mines were laid at 1 meter spacing in two diagonal strips across each panel. The mines were buried either flush or just below the ground but were not camouflaged.

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Tripwires were attached to each of the MUV 3 fuzes on the OZM 4's. These were deployed to ensure that the machine struck the mine first 6 times, the tripwire first 7 times and both simulanteously 5 times.

The test area was designed to ensure that mines detonated individually for ease of recording and to be compact to reduce the amount of ground that needed to be cleared by hand. A plan of the test area is attached at Annex B and photographs are at Annex C.

A cordon was maintained 300 metres from the mined area by the MMC team throughout the trial. It consisted of 30 locally employed guards and a series of stakes, tapes and warning signs.

6.         Timings. The timings for the test were as follows:

Concept of MMC Operations

7.        First Machine. The first machine is designed to detonate mines and clear trip wires and vegetation. It has a rotating steel tiller with tungsten teeth which covers a 3 metre wide strip of ground up to a depth of 50 cm.

8.       Second Machine. The second machine is designed to disrupt or detonate any mines remaining, after the first machine process. It has two counter rotating steel tillers which "mulch" the soil and break up any large solid objects. It cannot however, break steel cased fragmentation mines. During normal operations the second and first machine work together in echelon formation however, for ease of recording detonations they operated individually during the trial.

9.        Third Machine. The third machine is designed to bring any remaining Mines (particularly steel cased mines) to the surface for visual identification and subsequent disposal. It is a wheeled armoured tractor with a plough and a cabin capable of accommodating up to 6 "spotters". It also features a crane with an electromagnet device for moving steel cased mines. This machine is supported by hand deminers to conduct demolition's. Photographs of all the machines are attached at Annex D.

Method of Assessment

10. The trial was assessed using an observer inside the machines as they operated and an observer at the control point. The number of detonations was confirmed after each

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machine completed a pass along the length of the test area. Two distinct types of detonation were heard, full detonation of main charge and detonators from the PMD 6 initiating outside the mine. Due to the construction of the PMD 6, in many instances detonators attached to fuze mechanisms fell out of the explosive charge as they passed thorough the machines.

Accurate assessment of the results was not possible until after the ground had been cleared by hand and all mines were accounted for. Results were divided into four categories:

 The status of cased explosive debris (category c.) was specified prior to the test in the letter attached at Annex E.

Mines in category d. were assumed to have been completely disrupted with no identifiable fuze componants remaining. Due to the thoroughness of the hand clearance and the clarity with which detonations were heard this assumption is reasonable.

Disruption is the process by which mines are broken up as opposed to detonation which refers to a mine functioning as designed. For the purposes of the trial a mine was considered completely disrupted if no cased explosive remained and partially disrupted if cased explosive was located after the mechanical clearance.

Mechanical Processes

12.     First Machine. The first machine used 6 overlapping passes to cover the test area, tilling the ground a depth of 300 mm. During this process which took 45 minutes of operating time 149 detonations were counted. The detailed results from the first machine process are attached at Annex F. It was also noted during this process that some PMD 6 mines had passed through the machine and remained completely intact.

13.     Second Machine. The second machine used 10 overlapping passes to cover the test area twice. Durrng this process, which took a total of 1 hour 40 minutes, 19 detonations were counted. The detailed results of this process are attached at Annex G. The number of mines which were disrupted during this process was not known until the hand clearance of the area was complete.

During this process one detonation occurred in panel 7 whilst the machine was in panel 12. This was probably the result of a MUV pin responding to a slight stimulus causing the striker to fire. Also, it was noted that at least two OZM 4's detonated under the machine in a buffer panel indicating that mines were moving from their original locations as a result of machine processes.

On the final pass of the second machine three OZM 4's were spotted in panel 12. In an attempt to disrupt these mines the tiller was lowered and the machine reversed over the area. The OZM 4's remained intact and were not located by the third machine. Had the tiller been raised the mines would have remained on the surface and could easily have been located.

14.        Third Machine. The third machine used a total of 30 passes to cover the test area six times. During this time one OZM 4 was recovered from panel 9 using the electromagnetic device and placed to the side of the test area for demolition. A partially disrupted PMN 2 was rnarked in panel 11 for subsequent demolition. The whole process took- around 3 hours.

The OZM 4 was removed from the test area during the first pass, however, the PMN 2 was marked and remained in place until all passes were complete. Therefore, the area surrounding the PMN 2 was avoided by the machine. Had there been any other mines in this area they would not have been unearthed by the third machine.

Hand Clearance

15.     On completion of  MMC operations the entire test area was searched by hand over a period of 6 working days. Thirty experienced deminers from the UN ADP were employed on this task. They used a combination of electronic instrument and manual excavation search techniques and shifted all the ground tilled by the machine (600 cubic metres). Photographs of the hand clearance are attached at Annex H. During this search the following items were located:

  A detalled record of iterns located by the hand clearance operation is attached at Annex I. Photographs of the debris are attached at Annex J.

Final Results

16.       The results of the MMC trial are shown below:

Detonated:

4

 Found by third machine:

The 94 mines not detonated or located by the third machine were accounted for as follows:

Partially disrupted:

Completely disrupted:

Conclusions

17.    The test achieved its aim by providing a quantifiable record of the performance of the rnachines. All of the mines were either detonated or disrupted to various degrees. However, 38 items of cased explosives remained uncleared including four OZM4's with fuzes sheared off.

Mike Croll
UN ADP Operations Advisor

Annexes:

A      Photograph of test area
B      Plan of test area
C      Photographs of test area
D      Photographs of the machines
E      Memo from CTA on safety criteria for MMC trial
F      Results of first machine process
G      Results of second machine process
H      Photographs of hand clearance
I       Record of items found during hand clearance
J       Photographs of debris

5

Annex A to
Report dated
30. May 1996

Photographs of Test Site

General area view

Close up of ground showing mines being laid

Annex B to
Report dated
30. May 1996

MMC Test Minefield Layout

Annex C to
Report dated
30. May 1996

Test area showing marking stakes

PMN mines in panel 2

Annex D to
Report dated
30. May 1996

Photographs of Machines

Appendix 1 to
Annex D to
Report dated
30. May 1996

Photographs of Machines

Annex E to
Report dated
30. May 1996

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SAFETY CRITERIA FOR
MECHANICAL MINE CLEARANCE
TRIAL 6 - 10 May 1996

1.     The following criteria are to be applied for the duration of the ADP-coordinated trial for the Krohn system mechanical mine clearance machines. These safety criteria relate to the debris remaining after the machines have passed through the minefield and completed all of the required passes. These are the minimum safety standards.

All debris is to be checked

Any debris which consists of explosive still contained in its casing is to be regarded as UNSAFE and it is not be handled. It must be destroyed in situ using approved explosive disposal methods.

Any debris which consists of the fuzing system which has not functioned as intended is to be regarded as UNSAFE and it is not be handled. It must be destroyed in situ using approved explosive disposal methods.

Any debris which consists of the top plate or percussion cap is to be regarded as UNSAFE and it is not to be handled. It must be destroyed in situ using approved explosive disposal methods.

Any debris which consists of an empty mine casing, that is, that it does not contain any explosive or explosive components is to be regarded as SAFE and may be handled and cleared from the minefield.

Authorised By:

Date: 4 May 1996

G. P. LINDSTROM
Lieutenant Colonel
Ammunition Technical Officer
Chief Technical Adviser
Accelerated Demining Programme

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Annex F to
Report dated
30. May 1996

Record of First Machine Performance

Annex G to
Report dated
30. May 1996

Record of Second Machine Performance

Number of mines detonated = 16.5% of total remaining

Time required for 10 passes = 1 hour 40minutes

Annex H to
Report dated
30. May 1996

Photographs of Hand Clearance

General view of hand clearance

Deminer at work. Note the excavation technique combined with electronic detector

Annex I to
Report dated
30. May 1996

Record of items found at the test site after MMC operations

Other items found

Annex J to
Report dated
30. May 1996

Photographs of Debris

OZM 4

MUZ fuzes with detonators attached