Paste backfill thermal contraction: Red Lake operations case study

One of the earliest attempts at field measurement within hydraulically placed cemented backfill occurred over 20 years ago. Recently, Thompson et al. (2014a) published their findings on capturing thermal expansion within cemented paste backfill (CPB) and cemented hydraulic backfill (CHB). They discovered that the total earth pressure within the CPB following placement is likely to increase at a rate of 30 kPa/°C (i.e. for an 11°C temperature increase). However, Thompson and his co-authors' research did not elaborate on the subsequent effects of thermal dissipation (or thermal contraction) in backfill. A comprehensive literature study concluded with no clear evidence of thermal dissipation phenomenon and its effects in backfill. It is hypothesised by the authors that if thermal expansion can occur, then thermal dissipation or contraction is also likely to occur. Red Lake operation (RLO) of Evolution Mining conducted a field program to capture the characteristics of the CPB during a transition from a plug–cure–main pour strategy to a more aggressive pour strategy (i.e. continuous pour operation). During this investigation, strong evidence of thermal contraction was observed in three of the four instrumented stopes. This paper presents detailed findings of two of the instrumented stopes.