Abstract
Backfill is increasingly used in underground mines worldwide. Its successful application depends on the stability of the barricades built at the base of the stopes to hold the backfill in place, which in turn depends on the knowledge of the pore water pressure (PWP) and stresses during, or shortly after, the placement of the slurried backfill. Until now, self-weight consolidation is usually considered for the estimation of the PWP. There is no solution available to evaluate the total and effective stresses during, and shortly after, the filling operation. As excess PWP can simultaneously be generated (increased) and dissipated (decreased) during the backfilling operation, effective stresses can develop when the filling rate is low and/or hydraulic conductivity of the backfill is high. The arching effect has to be considered to evaluate the effective and total stresses in the backfilled stopes. In this paper, a pseudo-analytical solution is proposed to evaluate the effective and total stresses in backfilled stopes during the backfill deposition on a permeable base, by considering the self-weight consolidation and arching effect. The proposed solution is validated by numerical results obtained by Plaxis2D. A few sample applications of the proposed solution are shown.
Highlights
Backfill is largely used in underground mines to fill stopes [1,2]
When the mining backfill is transported by boreholes and pipelines, it must contain sufficient water to ensure workability and facilitate transportation
Equation (12) is the analytical solution to evaluate the pore water pressure (PWP) in the slurried material during the backfill deposition on a pervious base, which was proposed by Zheng et al [51] based on the model of Gibson [31]
Summary
Backfill is largely used in underground mines to fill stopes [1,2]. The benefits of backfilling include, improved ground stability, reduced mineral dilution, and increased ore recovery [3,4]. The self-weight consolidation is largely considered for the estimation of the PWP during the placement of the slurried backfill, without any consideration of the effective stress development [31, 46,47,48,49,50,51,52]. The question is how to evaluate the total and effective stresses during, and shortly after, the filling operation (the most critical moments for the stability of barricades). To reply to this question, the self-weight consolidation and arching effect should be jointly considered.
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