1949 offer critical insights into the mechanisms of heat generation and transfer in reactive environments and have led to strategies to unlock longer sleep times through the early detection and mitigation of reactive ground risks. This research supports the safe and sustainable implementation of innovative blasting technologies and contributes to the broader advancement of mining science. KEYWORDS Long Sleep Times, WebGenTM, Wireless Blasting, Reactive Ground. All information contained in this document is accurate and up-to-date as at the date of issue. Since Orica Group Companies and the Authors cannot anticipate or control the conditions under which this information and its products may be used, each user should review the information in the specific context of the intended application. To the maximum extent permitted by law, the Orica Group Companies and Authors will not be responsible for damages of any nature resulting from the use or reliance upon information in this document. No express or implied warranties are given, other than those implied mandatory by law. 1. INTRODUCTION Modern mining operations are increasingly adopting wireless initiation systems like WebGen™, that eliminate physical detonator connections and enable remote firing of blasts through rock, air, or water. This technology is applicable in open cut and underground mines. The uptake has been more rapid in underground operations because of the enhancements to mining safety and productivity by allowing multiple blasts to be preloaded and fired without requiring personnel to re-enter hazardous areas. However, with these benefits comes a new challenge: dramatically longer “sleep times” (the interval between starting to charge a shot and firing it) are now often necessary to implement safer and more productive sequenced blasts. Wired and non-electric initiation systems demand continuous personnel access to connect blastholes, so shorter sleep times are less of constraint. Wireless initiation enables novel mining methods that require explosives to sleep for months. Designing bulk explosives that will be stable for months in reactive ground is a critical science and engineering challenge to realise the benefits of these methods. Reactive ground refers to rock containing sulphide minerals (e.g. pyrite) that can undergo a spontaneous exothermic reaction upon contact with ammonium nitrate (AN), the oxidiser in most commercial explosives. When the heat generated by reaction cannot be dissipated temperatures can escalate dangerously, this is known as thermal runaway. The reaction between AN and sulphides has a highly variable induction time and can generate intense heat, potentially leading to premature or unplanned detonation of the explosive charge (Rumball, 1991). This is a serious safety hazard. Hot and reactive ground conditions have caused multiple premature detonation incidents in the industry, with at least 13 known unplanned detonations between 2010 and 2019, resulting in 6 fatalities and 15 injuries. These statistics demonstrate that maintaining explosive safety during extended sleep is vital to prevent future incidents. To mitigate reactive ground risks, explosives manufacturers developed reactive ground tests to identify reactive ground and inhibited explosive formulations that suppress the AN-sulphide reaction. These inhibited products substantially delay or prevent the runaway reaction, allowing charges to sleep longer in reactive ground. Even so, current guidelines and industry practice limit routine sleep times in reactive ground to about 7 days. For example, the Australian AEISG Code of Practice for Elevated Temperature and Reactive Ground (AEISG, 2020) details the industry standard isothermal54 reactive ground test and mandates 54 Isothermal tests target a set temperature but may not account for heat transfer between the test sample and the apparatus or environment.
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