Clay Waste Pond Reclamation by Sand/Clay Mix or Capping

Abstract

During the phosphate beneficiation process, substantial quantities of waste clays are produced that are typically disposed of in large impoundment areas. Due to the low permeability and self‐weight of these clay slurries, years are required to achieve a consistency conducive to reclamation. Accordingly, the objective of this research is to compare reclamation schemes of sand/clay (s/c) mix versus capping for enhancing consolidation of these waste clays. These comparisons are accomplished analytically using a closed‐form solution to estimate magnitudes and a finite strain consolidation computer program to determine rates, while centrifugal model tests provide experimental data. From these comparisons, it is found that the descending order of reclamation scheme effectiveness in achieving the highest final solids content is: (1) Sand capping (staged); (2) s/c‐mix capping; and (3) using s/c mix, provided surface drainage is maintained and caps do not become buoyant. The time required, however, is proportional to the solids content; e.g., higher solids contents require longer times.