Investigation into changes in pastefill properties during pipeline transport

A critical parameter in the design of pastefill distribution systems is the shear yield stress of the backfill. Yield stress is used in the hydraulic modelling to estimate the friction losses in the system and is generally assumed to be constant throughout the piping system. However, many sites report a change in slump during transport - sometimes up to 50 mm. As slump is used as an indicator of yield stress, it can be hypothesized that that material rheology is changing during transport potentially due to changes in particle shape and size or pastefill temperature. By sampling pastefill at the surface and at the discharge point underground, in two Canadian mines, this study shows that the yield stress and temperature of pastefill does not remain constant through the distribution system. The size and shape of the backfill particles are analyzed and no remarkable changes are found. The effect of temperature on the yield stress is investigated through laboratory testing using slump tests and a rotational viscometer and indicate that temperature is a significant factor in the yield stress change.