Estimating the Clearance Depth Required in UXO Contaminated Areas NSGG

Transcription

1 Estimating the Clearance Depth Required in UXO Contaminated Areas NSGG

2 Michael Laneville Principal Geophysicist MMG LXML Sepon UXO Department

3 Factors Affecting Clearance Depth 1. End land use requirements 2. Detection limitations 3

4 Sepon Gold and Copper Operation 4

5 UXO Contamination at Sepon Main contamination: cluster bombs (bombies) aircraft bombs Ground fighting was not prevalent. The primary military activity in the area included anti-aircraft positions, logistics and personnel staging areas. 5

6 US Bombing Data Must have knowledge of UXO present. Detailed US aerial bombing records have been made available to assist humanitarian demining in Southeast Asia. Information available includes: Type of ordnance Payload Aircraft type Date of mission Coordinates 6

7 Quality of the US Bombing Data The US bombing data is not perfect. There are issues including: omitted data incorrect datum transformations target points vs. release points According to the Geneva International Centre for Humanitarian Demining (GICHD); if properly validated, analysed and utilised; there is significant potential to its use. The US is expected to release a revised and expanded database which will: fill in gaps of several months that currently exist include Navy and Marine Corps data attempt to remove several known inaccuracies 7

8 Soil Types Must have knowledge of soils types present. Sepon drills hundreds of holes each year for exploration work throughout its mining lease. In mining pits, thousands of regularly spaced holes are drilled to define the limits and concentration of ore. In both cases, information including soil type and hardness are recorded. 8

9 Making a Better Model The UXO Department is currently working on a computer program to model the expected UXO distribution at Sepon on a site by site basis. Input Data: Topographic data (Lidar) US Bombing data Soil hardness data Pit design Additional assumptions: UXO failure rate Striking velocity Horizontal bomb distribution Vertical bomb distribution As far as any model goes, the quality of the Input Data and Assumptions are high. Sepon is very rare to have such a rich set of inputs to work with. 9

10 How Many Bombs Dropped are UXO? During the war, B52 planes which were mainly used to bomb Laos had failure rates as high as 30%. All US bombing data is directly scaled by this amount. For example, 100 bombs dropped becomes 30 UXO which we expect to remain. 10

11 Estimating Penetration Depths Bomb penetration lengths can be calculated for a given soil type and bomb weight and a varying striking velocity. The hardness scale used at Sepon has been approximated to this graph. H0 This graph has been described mathematically and compared with existing penetration depth equations. H3 H1 H2 We will assume the maximum striking velocity. H5 = H4 Source: U.S. Army, Training Manual TM ,

12 Distance from US Bombing Data (m) Validating the US Bombing Data Approximately 100 recovered UXO (bombs) found to date at Sepon have been compared with the closest point in the US bombing data. 50% of UXO have been found within 190m of the nearest point in the bombing data; 90% within 1200m. We will use this relationship to distribute the bombs laterally. Correlation of UXO Found at Sepon Compared with US Bombing Data % of UXO Found 12

13 How Many Bombs Reach the Max. Depth? Ordnance typically follows a J-shaped trajectory resulting in a decrease in penetration depth US Army Corp of Engineers (USACE) studies confirm that the actual depth of penetration for most items is much lower than the maximum depth. Using these study results and our own recovered items, we can estimate the vertical distribution of UXO as related to their maximum penetration length. 13

14 Putting it Together At this point, the US bombing data has been: 1. scaled for failure rate 2. given a striking velocity penetration depth 3. distributed laterally 4. distributed vertically We can now map the data in terms of UXO/m 2 The geology can now be considered. In a homogenous area, our equations can give us the maximum penetration length of each type of ordnance. In a simple case, we have now defined the maximum search depth required. 14

15 Program Sample Views 15

16 Computer Outputs Polygons at user requested depth intervals showing where UXO search is required. Summary files for the area of study describing: types of UXO numbers and density of UXO expected number of UXO at various depth intervals topographic and geologic data Complete 3D visualization of estimated UXO distribution. 16

17 Conclusions & Going Forward This program is a tool to be combined with others when creating a clearance strategy. Has the potential to rate relative UXO risk or identify opportunities for land release. The model must be tested and allow for feedback from real data. Work must be done to improve the quality of assumptions. Garbage in = Garbage out. 17

18 Thank You! 18