Excess pore pressure generation during slurry deposition of gold tailings

Abstract

ABSTRACT Excess pore water pressure (PWP) in gold tailings, deposited in the laboratory in a settling column, was observed for various rates of deposition. Rates of rise (vertical increase in height of settled tailings over time expressed in metres per year) of 10 m/yr and 20 m/yr were evaluated by depositing the gold tailings in layers. The maximum deposition rate achieved in the laboratory by depositing tailings to the full height of the settling column at once (full depth deposition) was also investigated. Maximum excess PWPs of 6 kPa generated within 3 to 9 minutes from the start of tailings slurry deposition were recorded. 90% of the maximum generated excess PWPs dissipated within the first 10 hours for coarse tailings and 30 hours for fine tailings. Dissipation of the remaining 10% occurred within 1.1 days and 10.4 days respectively. The excess PWPs were the highest for full depth (FD) deposition. Excess PWPs at an rate of rise (RoR) of 20 m/yr and 10 m/yr were 50% and 30% of the FD deposition. Dissipation of the excess PWPs occurred mostly during the sedimentation phase. It is shown that excess PWP build up on its own cannot be the mechanism that limits the RoR of gold tailings dams.