THE PROPERTIES OF CEMENTED SILICATED BACKFILL FOR USE IN NARROW HARD-ROCK, TABULAR MINES

Several aspects of The behaviour and properties of backfills consistin g of cemented cyclone-underflow tailings are illustrated by means of e xamples, and guidelines are given on the optimization of the performan ce of cemented fills. The stretch characteristics of the geofabric use d to contain freshly placed backfill are described, as well as the rel ationship between these characteristics and the forces acting on retai ning barricades. The properties required to achieve a self-supporting, stable free face in cemented backfill are explored, and a graphic rel ationship between stable height and shear strength is presented and co mpared with that for uncemented (classified) tailings. After a descrip tion of the characteristics of Witwatersrand quartzite gold-tailings b ackfill and commonly used cements, the process of drainage and air ent ry into backfill is outlined, Following this, the early-age gain in st rength and the shear-strength characteristics, as well as the compress ibility characteristics of cemented backfill, are described. Two pheno mena that are potentially damaging to cemented backfill are seismic ef fects (or blasting acceleration) and the closure that takes place duri ng the curing of cement, Investigations show that neither of these phe nomena is actually significantly deleterious to gold-tailings backfill : liquefaction does not occur as a result of seismicity, and hydration of cemented fill not significantly impeded by closure.