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Paste fill is the newest form of backfill material in the spectrum available to international mines and is made from full mill tailings. Tailings have an effective grain size of approximately 5 lm and are combined with a small portion of binder and water to make paste. It is deposited into the voids created by mining which are referred to as stopes. The empty voids are approximated as vertical rectangular prisms, with plan dimensions of 15-40 m and heights of 100 m or more. Backfilling of mined stopes provide an increased level of local and regional stability to the ore body, as well as providing a suitable and economic dump of mining related waste. Paste is a relatively new technology in the mining industry and a review of the physical properties and mechanical fill behaviour was considered pertinent.

Permeability is one of the most important parameters in the design of hydraulic backfilling of mine stopes. A simple and reproducible method was developed for preparing reconstituted hydraulic fill sample in the laboratory, that is representative of the hydraulic fill in the mine stope, replicating the slurry sedimentation process taking place in the mine. Constant head and falling head permeability tests were carried out on the samples, giving consistent results. A brick permeameter was developed to study the flow characteristics of the porous barricade bricks under one-dimensional flow, simulating the flow conditions in the mine. Three different methods were used to determine the permeability of the brick and the results showed very good agreement. This is the first rational attempt to measure the permeability of the porous barricade bricks that are used to close the horizontal access drives in the mines, thus retaining the hydraulic fill. The measurements show that the permeability of the barricade brick is about two to three orders of magnitude greater than that of the hydraulic fill.

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