Cemented tailings backfill is generally prepared by mixing waste mining tailings, water, and cement to give designed outcomes. The CTB preparation recipe with 20 wt.% water (by total mass) and 80 wt.% solids (by total mass), which contains 6 wt.% (by solids mass) binder proportion (Portland cement : fly ash 4:1), was recommended for the Sustainable Mining by Drilling (SMD) Project. However, due to the relatively high cost of Portland cement, investigations of the use of lower binder proportions and optimization of backfill strength development were carried out. In this paper, the effects of (i) lower binder proportions (2 wt.% and 4 wt.% by solids mass), and (ii) internal vibration on the designed CTB density, unconfined compressive strength (UCS), tensile strength, and the amount of tailings usage were evaluated. The results showed that the 4 wt.% binder backfill specimens obtained 1.035 (avg.) MPa compressive strength after 28 days curing time, which reached the designed target compressive strength of CTB. The results also showed that the fully vibrated CTB specimens possessed 14.7% higher density and 57.1% higher compressive strength than the specimens without vibration, which means that an extra 10.9% tailings can be placed into extracted wellbore when the CTB is fully vibrated. This behaviour allows more tailings to be securely placed underground and further reduces the surface tailings impoundment requirements and the costs of tailings disposal for the mining industry.

1. Introduction

Mining industry produces extracted voids in varying shapes, including stopes, tunnels, goafs, and gob voids. The extracted voids create instability risks for the excavation of adjacent pillars holding minerals, along with a subsidence danger for on-the-ground personnel and machinery during mining activities or after a mine has been decommissioned. Collapse of the created voids is one of the main factors in rock burst and potential land subsidence (Helm et al., 2013; Wang et al., 2013). Over the last few decades, the volume of tailings being generated increased dramatically due to the increase in the demand for minerals and metals and the mining of many low-grade ores. Mining industry faces the daunting challenge of environmental issues associated with the management of tailings.

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