CONSOLIDATION OF COMPACTED SLUDGE-CRUSHED SALT MIXTURES AS BACKFILL IN POTASH MINES

Abstract

Mechanical performance of consolidated sludge-crushed salt mixtures is determined for use as backfilling material in potash mines. Crushed salt with sizes ranging from 0.075 to 2.35 mm is prepared from Lower member of Maha Sarakham formation. Sludge has been obtained from the Metropolitan Waterworks Authority of Thailand. The sludge-to-crushed salt mixtures having weight ratios from 30:70 to 70:30 are compacted to determine their optimum brine contents. The compacted specimens are then consolidated under constant stresses from 2.5 to 10.0 MPa for up to 30 days. The results indicate that compressive strengths, elastic moduli and Poisson’s ratios of the mixtures decrease with increasing sludge contents and increase with consolidation stress and period. Mixing crushed-salt with sludge can reduce long-term consolidation rate of the mixtures. This is primarily because sludge composes mainly of fine particles of quartz which can fill voids between crush salt grains.