Hydraulic response in cemented paste backfill during and after hydration

Abstract

The distribution of pore-pressures in mine stopes may have important implications to the design of cemented paste backfill (CPB) systems. Self-weight consolidation after filling stopes is inherently problematic when pore-water pressures begin to develop. However, during cement hydration, self-desiccation begins to occur and consequently, pore-water pressures gradually dissipate. In some cases, during self-desiccation, matric suctions can develop within stopes, depending upon adopted mining strategies such as, fill rate and percent water to binder content. Tracking the evolution and quantifying the hydraulic behaviour in cemented paste is rather difficult because of the complexity of the hydrating material. The current study investigates and attempts to capture CPB’s transient responses during and after cement hydration through a series of self- desiccation tests and axis translation tests. Self-desiccation tests are conducted on cemented paste specimens containing 0, 3, 5 and 7% wt binder material. The water-retention properties of the material are measured without binder, and after 28 days of hydration. This data is then used to approximately model the dissipation of pore-water pressures measured at the bottom of stope during a plug pour. The approach shows promise. Significance and future improvement to the proposed methodology are discussed.