OceanaGold Waihi North Project Vibration Performance Assessment Page 18 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 w is the maximum quantity of explosive per delay measured in kilograms, and K and α are site constants. The term in brackets (d/√w) is referred to as the scaled distance term. All blasts are monitored where vibration above the threshold of 0.75mm/s has occurred. There are also some occasions where lower thresholds have been utilised for specific purposes of analyses. The vibration levels have been regressed against the value of the scaled distance term, calculated as the distance between the blast and the monitoring site divided by the square root of the explosive quantity, to establish a relationship that can be used to estimate the level of vibration from various blast designs. Some of the monitors, such as the Ventilation Shaft monitor for the underground mine, are positioned at locations closer than the nearest affected residence and compliance with the vibration criterion is not required. On some occasions, vibration levels above 5mm/s have been recorded at this location. These vibration data are either used to assist with regression analyses or to assist with confirmation of a blast event and do not indicate any degree of non-compliance. The data show that there is variability in vibration levels as a function of the scaled distance term. There are occasions where a similar scaled distance value, that is a combination of distance and explosive weight, yields vibration values less than 0.75mm/s and yet on other occasions more than 10mm/s. The variability is however typical of that produced from a very large data sets that incorporates multiple projects completed over an extended period of time. The variability could be associated with multiple aspects and includes, but are not limited to: Varying geology with more competent rock masses leading to higher levels of vibration. Varying degrees of confinement with confined blasting expected to produce higher level of vibration than undertaken with a free face. Differences in the blasting practices, including variations in the explosive types and performances. Varying initiation systems ranging between conventional pyrotechnic delay elements and the accurate electronic elements. Initiation patterns, including the direction of initiation and the number of blastholes sharing a common nominal delay time. Varying levels of quality control associated with the blast loading process, including improvements in the accuracy of delivery of small explosive quantities. The degree of water saturation around the blast region, the monitoring location or the intervening ground between these two locations. The presence of old workings which could either shield or elevate the level of vibration. Varying localised ground conditions around the monitoring arrangement. An unbiased statistical regression of all the recorded data shows almost no relationship between vibration level and scaled distance with a coefficient of regression (R2) of 0.1. A value of 1 reflects a perfect relationship and 0 indicates no relationship. The calculated α term, as per the Australian Standard equation, is -0.42. It is however known through other work at Waihi, and as reported in the peer reviewed international literature, that the value for α commonly lies between -1.2 and -2, depending upon rock type and other blasting parameters. Vibration studies that have been completed at Waihi have linked the level of vibration with the distance from the blast and the quantity of explosive initiated at a given time. These studies have generally found that the whilst the “K” parameter in the vibration equation varies according to the blast area and other aspects of blasting, the α term remains consistent at around -1.49. There appears no justification that any analyses should consider that the α term would vary from the value of -1.49. The vibration from the proposed GOP areas has been assessed using vibration data nearest to that area (the Moonlight underground mine). Given that no vibration data have been recorded around the
RkJQdWJsaXNoZXIy MjE2NDg3