OceanaGold Waihi North Project Vibration Performance Assessment Page 13 of 41 Project Number: HP2006-2 Heilig & Partners Save Date: 21/06/2022 5:55:00 PM ABN 56 082 976 714 File Name: WAI-985-000-REP-LC-0018_Rev 0 Drilling and blasting will be required for the removal of the ore and rock for all areas, possibly excluding some of the upper areas of the GOP which may be free dig. The type of blasting differs according to whether it occurs for the underground mine, open pit or tunnels, but will be consistent with that undertaken for the previous Martha open pit and underground operations. Blast patterns for the open pit operation tend to be simpler than those for underground blasting, involving drilling of blastholes on a regular pattern to a consistent depth, loading a known quantity of explosive into the base of the blasthole, adding stemming material to the blasthole above the explosive column, and initiating the blast with a series with small intervals between successively detonated blastholes. 7.1. Gladstone Open Pit The scale of blasting for the GOP will be one that promotes environmental compliance, and in particular, compliance with the vibration restrictions. Over the previous 30 years, the Martha operation has undertaken blasting practices aligned with conventional small scale drilling and blasting operations and achieved a very high percentage of blasts that have generated less than 5mm/s (>99%). Drill and blast for the GOP will be a stepped process and involve the following stages: Design of drill and blast patterns, including burden and spacing, hole depths, air decks, explosive weights and number of blastholes, are detailed in a pre-blast plan; The drilling pattern will be marked out in accordance with the prepared plan. The blast pattern will be loaded according to instructions in the Vibration Management Plan, The firing of the drill and blast pattern will be sequenced using inter-hole delays that best promotes minimum vibration levels and achieves the required fragmentation and diggability. Mining of the GOP will be designed around 5 metre benches. The blasthole diameter is expected to be consistent with current blasting practices, at 89mm. The blasting configuration for a 5 metre bench height with ½ metre of sub-drill, an 89 mm diameter blasthole, a 2.6 metre uncharged collar height and loaded with bulk explosive. The uncharged collar length of 2.6 metres is proposed to limit air overpressure levels and control any ejection of material from around the blasthole. The explosive density typically lies between 1.15 and 1.20g/cm3. 7.2. WUG Production Blasting The WUG production stopes are planned as the main source of ore from the underground operation. The stope sizes are typically small, around several thousand tonnes, and constrained by the geometry, particularly the width, of the orebody and the geotechnical parameters that define its stability. In general, it is anticipated that stope sizes will be consistent with the Favona, Trio and Correnso underground operations, with distances between sub-levels varying between 12 and 20 metres (back or roof of one level to the floor of the level above). Larger sub-level intervals require greater explosive weights which are likely to be used in the deeper sections of the mine. Blasthole diameter will be small and lie in the 64 to 89mm diameter range. Explosive type will depend upon ground conditions and vibration constraints however a low density bulk emulsion, low density ANFO or ANFO will be typically used. These explosive types are consistent with the current underground operations. The explosive density typically lies between 1.15 and 1.20g/cm3. 7.3. Tunnel and Decline Blasting Tunnel or decline blasting is small scale horizontal or slightly angled blasting specifically undertaken to provide access to the orebody for the subsequent larger production blasting activities, or to provide a tunnel between key areas, such as the WUG orebody and the process plant. Development blasting is significantly different from production blasting. The differences include:
RkJQdWJsaXNoZXIy MjE2NDg3