Water table management in Hydraulic fill masses

9th International Symposium on Mining with Backfill
Matthew Helinski, Tony Grice, Cameron Tucker,
Abstract High hydraulic conductivity in hydraulic fill masses combined with the non-plastic nature of most hydraulic fills makes susceptibility to piping failure a high possibility in many hydraulic backfills. In order to achieve a piping type failure within a hydraulic fill mass a static head of water must exist above the fill material. As a result many hydraulic fill operations adopt a filling and resting criteria to ensure that the phreatic surface remains below the fill surface. Due to many complicated characteristics simulation of stope drainage can be extremely difficult. Therefore, a conservative approach is often adopted. This conservative approach can lead to significant delays in the filling cycle which can have a major impact on the productivity of many hydraulic fill operations and can often results in a movement to adopt a more capital intensive paste fill system. This paper presents a technique for monitoring the elevation of the phreatic surface in a hydraulic fill mass and illustrates how this technique may be used to manage hydraulic fill run-rest times in an efficient manner. The implementation of this strategy has lead to a significant increase in filling rates at a number of Australian filling operations without compromising safety.
Keywords: Insitu monitoring, Hydraulic Fill, Water management
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