OFFICIAL factors of safety are applied in determining if the Marathon i TM product range is qualified for the 90-day sleep time at that site. Comsol Multiphysics Modelling COMSOL Multiphysics® is a general-purpose simulation software used in all fields of engineering, manufacturing, and scientific research. The software brings fully coupled multiphysics and single-physics modeling capabilities. The Heat Transfer Module for investigating thermal effects of heat loads, the temperature fields and heat fluxes are determined based on the three modes of heat transfer: conduction, convection, and radiation (COMSOL, 2026). To better understand how heat flows between different bulk explosives products and the ground, a blast hole was modelled in COMSOL. A 229mm diameter borehole was modelled with a 1m self-heating seam 4m from the collar, shown in Figure 6. A starting temperature of 70 oC was chosen for the coal seam, a key safety limit of many initiating systems. This scenario is relevant because it has been identified in some hot and reactive ground incidents in coal mines and the processes are similar to reactive ground. In future the results of the reactive ground kinetic studies can be used as inputs to the same model to investigate different real-world conditions. The following assumptions were used to establish the model: I. Thermal properties of ground, coal, bulk explosives and stemming aggregate were independent of temperature, such that heat capacity, thermal conductivity and density are constant. II. The heat effects of radiation were negligible. III. The blasthole was cylindrical and this sits within a rectangular prism of ground. IV. Model width was 2 meters as radial conduction into surrounding ground becomes negligible. V. There was a heat source (Q) only at the coal surface of 45 W/m2, due to the presence of exposed active sites which cause the seam to interact with oxygen or loaded products. VI. Natural convection governs fluid flow due to temperature, and hence density, differences, with no forced convection. This means all air flow was controlled by buoyancy forces. VII. The top of the blasthole was exposed to an infinite volume of ambient air, an “Open Boundary”. VIII. Bulk emulsion explosives, heavy ANFO, ground and coal are treated as a solid, whereas ANFO and stemming aggregate are treated as porous media. The models were all run to simulate 16 hours.
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