In Situ Monitoring of Cemented Paste Backfill for Improved Mine Design

9th International Symposium on Mining with Backfill
William Bawden,
Abstract Several research programs have attempted to monitor in situ the development of stresses within Cemented Paste Backfill in order to better understand how pressures develop on fill barricades, as well as how the fill may be more-or-less self supporting through the development of arching mechanisms. Most of these monitoring programs have used total stress cells, with a few also using piezometers to monitor water pressures that may develop within the fill. In some mines, however, the rate of filling which leads to development of hydraulic pressures and self-weight loading, is similar to the rate of binder hydration which can both reduce hydraulic pressures and resist self-weight loading by enhanced fill stiffness and arch development. It is therefore proposed that in situ monitoring programs need to track more variables related to the paste’s evolving mechanical properties and subsequent interaction with the stope boundary conditions. The proposed paper will discuss an instrument cluster that consists of both conventional monitoring approaches as well as complementary instrumentation based on electromagnetic and small strain dynamic monitoring techniques. Sample data will be provided from laboratory testing of the new types of transducers. The gradients for the variables of interest in typical stope geometries will be considered and the required number of instrument “clusters” or datapoints discussed. Finally, implementation of this in situ monitoring approach in three upcoming field trials will be considered, with particular attention paid to the logistical problems involved in mobilizing such clusters in an active mining environment.
Keywords: stress measurement, Paste backfill, electromagnetic monitoring, Hydration, Instrumentation
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