Hydraulic mining utilises high-pressure jets of water to re-pulp tailings and suspend it into a slurry, for the purpose of environmental clean-up, mineral extraction, or the mitigation of risk. This is typically done with the use of large water cannons, which can be mounted on skids, wheels or tracks for the ease of movement during operation.  Hydro Mining cannons are generally 100 or 150mm in diameter, with varying nozzle sizes for the adjustment of water flow and pressures. 

Water pressures of between 10 and 30 Bar (145 – 435 psi), are generally required to mechanically break and/or soften previously consolidated tailings to such a state that it can flow to a collection sump.  Pressures are site specific and a result of the tailings state and characteristics such as hardness, particle size, moisture content and location.  Lower pressure operations are far less complex than where high pressures are required for effective repulping.

Hydraulic mining cannons are strategically placed on the tailings surface to allow for redundancy and blending of various material characteristic types.  Grade blending, to allow for consistency and uniformity is easily achievable during mineral extraction operations.

A 150mm hydro mining cannon, at 30 Bar, with a 54mm nozzle will move 350 m3/h of slurry with a production rate of 260 dry tons per hour, at a density of 50% solids.    

The slurry gravitates from single or multiple mining areas to strategically placed collection points, where it is screened and pumped for re-treatment or disposal.    

There are two general hydraulic mining approaches – “top-down” and “bottom-up”. 

• During “top-down” operations, the water cannon is placed at the top of the mining face, with the water jets directed downwards – usually at a cut angle of between 25-35 degrees. This method provides good control over the mining face, controlled face stability and a clean, dry operation.
• “Bottom-up” operations requires water cannons to be placed near the toe of the mining face, with the jets projecting upward and into the mining face. This method undercuts the slope to collapse in a controlled manner.  These operations are normally associated with wet working areas, uneven face cuts and has the potential to expose equipment to the risk of possible slurry waves and slope collapses.           

Hydro mining techniques are adapted from site-to-site to cater for unique factors such as the size and location of the facility, availability-, volume- and pressure of water, as well as the hardness, particle size and moisture content of the material that are mined.