6 | P a g e Class 1 Storage Location Assessment_Oceana Gold NZ Ltd Wharekirauponga Underground Mine 4.1 Blast Propagation by Rock Spall In order to assess the likelihood of propagation between explosive chambers/ magazines by way of ‘rock spall’, ‘ Annex M’ of ‘IATG 2.20 ‘, has been referenced. In consideration of the ‘loading density’ (kg/m3) – this is the calculated volume ratio (kg/m3) stored within the explosive’s magazines – in this instance the proposed loading density can be shown in the following. In consideration of the maximum stored quantity of H.E per chamber, ( where Q = 1,000 kg ) Kg/ m3 = NEQ (kg)/ Magazine volume = 1,000 kg / 627 m3 = 1.6 kg/m3 In consideration of known loading density, ‘ ANNEX M ‘provides the following formula to establish a minimum separation distance between magazine storage in order to mitigate risk of propagation by way of rock spall. Where Loading Density < 270 kg/m3 D = 0.6Q 1/3 = 6.0 m is minimum distance In relation to the above scenario of ‘propagation by rock spall’, the minimum required offset between H.E storage chambers is 6.0 m. The current proposed design of 10 m wall to wall distance between individual chambers is therefore adequate to ensure sufficient mitigation control. 4.2 Blast Propagation by Flames and Hot Gases In order to assess the likelihood of propagation between explosive chambers by way of ‘Flames and Hot Gases, the methodology described in ‘ Annex M’ of ‘ IATG 2.20 ‘has been adopted. The ‘Chamber Interval Distance (CID)’ is the required distance between magazine chambers in order to mitigate risk of propagation by way of ‘Hot Flames and Gases’. ‘Annex M’ provides a range for CID from 0.3Q1/3 to 2.0Q1/3 to account for different rock mass conditions. Despite the expectation of competent rock mass conditions, a conservative estimate and scaling factor of ‘ 1.0Q1/3 ‘has been adopted. In reference to H.E magazine chambers (being the highest stored quantity), where Q = 1,000 kg) Required CID = 1.0Q1/3 = 10.0 m The minimum required CID between H.E storage chambers has been calculated at 10.0 m in order to manage potential impacts associated with ‘propagation by flames and hot gases. Therefore, the current proposed CID design of 10.0 m is acceptable.
RkJQdWJsaXNoZXIy MjE2NDg3