Effect of deep mine temperature conditions on the heat development in cemented paste backfill and its properties

As ore reserves available at shallow depths are diminishing in several countries, underground mining operations are moving to greater depths. This greater depth is naturally associated with heat influx increases because of the geothermal gradient. The exposed rock mass is the primary heat load source in any deep level mining operation. In this study, a numerical model is developed and validated to assess the heat transfer between deep mine rocks and cemented paste backfill (CPB) structures, as well as the heat development in CPB structures in deep mine temperature conditions. The numerical modelling results have shown that the initial deep mine rock temperatures significantly affect the heat or temperature development inside the CPB. Furthermore, experimental tests were carried out to study the effect of high temperatures on CPB properties. Different types of CPB specimens were tested at different curing times and temperatures. The strength, deformation behaviour, resistance to sulphate attack and hydraulic conductivity of these CPBs were evaluated by laboratory tests. Results showed that deep mine temperatures have a significant effect on the properties of CPB. Increasing the curing temperature increases the rate of CPB strength development and leads to higher early CPB strength and lower binder consumption. Moreover, the effect of temperature depends on the binder type, the curing time, the water content and the sulphate content of the CPB. Hence, the deep mine temperature is an important factor that should be considered in deep mine CPB operations in order to better optimise CPB mixtures and design cost-effective and durable CPB structures.