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NORDIC TECHNOLOGY

“Drill through test”, at the LKAB mine in Kiruna

reductions, effected by straighter drilling of long holes. These include:

  • Lower development costs

  • Larger scale of operation – lower cost per tonne

  • Less dilution

  • No need for extra drilling and less explosives needed

  • Better fragmentation - less handling of boulders.

Wassara drilling allowed LKAB to increase blasting yield about 1,200 t per round to around 10,000 t. This was done by increasing the distance between the sublevels. The straightness and good penetration rate made it possible to combine the enlarged blasts with good drilling results. The increase in the height between sublevels, from 12 to 28 m, means that there are almost half the sublevels required previously. With increased horizontal distance between the drifts, the total reduction of drifting in the ore is approximately 70%. This means less drifting and less rock reinforcement.

For LKAB, dilution from drilling/blasting has been calculated to be some 5%, and the straightness achieved by using Wassara made it possible to avoid increased dilution when

0,4 m

0,7 m

Row 1-3 Wassara

1,6 m

0,4 m 0,4 m

0,4 m

0,5 m

0,7 m

0,8 m

Row 4 Top-Hammer

1,7 m

0,8 m

3,9 m

53,8m

Row 1 Row 2 Row 3 Row 4

Average deviation for Wassara = 1,05%

increasing the distance between sublevels.

There are several examples of 10-25% extra holes being drilled underground to compensate for deviating blastholes and ensure good fragmentation. Drilling with Wassara, the average deviation can be trusted not to be more than 1-1.5%. This makes it unnecessary to drill

any extra holes, and explosive use can be optimised to these drilling results.

Straighter drilling will automatically result in better control over the fracturing of the ore mass when blasting. This makes it possible to reduce the number of oversize boulders, and thus the cost for secondary ore handling. IM

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