Paste backfill bulkhead failures and pressure monitoring at Cayeli Mine

摘要

The stability of bulkheads forms an integral part of a successful paste backfill system. Bulkheads are constructed at the draw points of open stopes to contain paste fill while the initial pour cures and forms a consolidated plug. Mobilization of uncured paste fill as a result of a bulkhead failure can lead to significant consequences, including endangering the safety of personnel, property damage and production losses and delays. This paper presents details of three paste fill bulkhead failures that have occurred during the late stage of tight filling transverse blind uphole retreat stopes in an underground base metal mine; the results of an in-situ instrumentation and monitoring program to ascertain the paste fill pressure loads acting on the bulkheads and to understand the pressure development mechanism within paste fill mass; and the subsequent changes made to the bulkhead design and paste fill placement sequence in order to prevent reoccurrence of bulkhead failures in the future. The revised bulkhead design and fill placement management has been successful because, to date, Cayeli has filled more than 50 blind stopes without any failure. A significant outcome of this study is that it has been shown that only a combination of properly engineered bulkhead design, bulkhead construction, and better management of fill placement can provide safe and efficient filling practices. Furthermore, bulkhead pressures are very site-specific and any bulkhead design should be based on. field pressure monitoring results carried out at the actual mine site.