PASTE & TAILINGS
Weir GEHO ® piston DHC 21220-VZ at Rosh Pinah, Namibia
Backfill to basics
Paul Moore looks at backfilling technology and equipment plus tailings pipeline innovation and monitoring
Mine backfilling is by no means a new technology, but there is an increased interest in it because it provides a solution to some of the most pressing challenges the mining industry is currently facing; notably, increasing volumes of tailings, while, at the same time, above ground storage constraints. Moreover, large tailings storage facilities( TSFs) present significant ESG( environmental, social and governance) and geotechnical challenges that mine backfilling can help alleviate or resolve. This was the topic of an August 2025 article by Weir.
There are, of course, also commercial drivers and backfilling can play a significant role in increasing recovery. Stopes can be stabilised and, as a result, miners can extract more ore, including previously inaccessible mineral resources. Weir:“ At the end of the day, the value of the ore processed, refined and sold offsets the cost of the backfill, so when there are strong commodity prices – like gold currently, which is at record highs – the economics of these projects are strengthened.”
Another thing that Weir has observed is that there seems to be a growing demand for higher capacity pumps, which is in line with the trend towards higher production rates and lower ore grades, which, by extension, means there are increased tailings volumes.
Tailings have historically been seen as a loss generating waste product that miners spent as little money on as possible, but that simply isn’ t an option anymore. Tailings management is heavily regulated, and an operation’ s tailings burden can, in some instances, determine whether it can continue production. There is also a greater awareness of and desire to mitigate the ESG risks posed by poor tailings management. Combined, all of this represents a significant shift in the industry – one that fundamentally changes the way miners operate.
As a result, tailings management continues to evolve. For instance, one thing that is becoming more common is that miners are combining both backfilling and surface storage as a means to help manage their tailings burden.
Weir:“ The fact that many above ground TSFs are reaching their capacity means that some operators are now looking to backfill mines that have never previously been thought of as good candidates for backfilling because it would neither increase recovery enough to justify the expenditure, nor was it required for geotechnical reasons. Instead, they are backfilling simply to reduce the above ground tailings burden. In some instance, they’ re even looking to backfill abandoned mines.”
It adds that one of the most challenging aspects when it comes to mine backfilling is getting the backfill recipe right. There are a lot of variables in the process and the material changes, which means the mixture, or‘ mix design’, has to change too.
Getting the right balance between water,
tailings, binder material( cement), and sometimes admixtures, is obviously a cost factor which often requires quite a lot of work.
From a pumping perspective, Weir points out that this concentration determines the yield strength of the slurry, which, in turn, determines how challenging it is to pump.
There is a technical limitation to the level of concentration because, while a high yield strength is desirable from a geotechnical point of view, if it cannot be pumped, then it cannot be used to backfill stopes.
There are typically two pump options for backfill applications – hydraulic-driven piston pumps and piston diaphragm pumps. Weir’ s product portfolio includes both the GEHO ® DH hydraulic piston pump and the GEHO ® T / ZPM piston diaphragm pump.
The presence of large particles is the primary factor that should define the pumping technology that needs to be used. However, Weir says it is the only OEM that has both the hydraulic piston pump and the piston diaphragm pump in its portfolio, which means that it can select the ideal pump for the application.“ This gives Weir greater flexibility and allows it to tailor solutions to the customer’ s specific requirements, rather than offering solutions based on its product portfolio.”
Given the difference in the material being pumped, the operating conditions and, by extension, the difference in the capabilities required of each pump, selecting the wrong technology for mine backfill applications reduces efficiency, increases wear and OPEX( operating expenses) and can lead to catastrophic failure.
“ Historically, hydraulic piston pumps have been used in concrete pumping applications, but they’ ve been adopted by the mining industry to pump mine backfill material, which typically includes a cement binder. But construction and mining are different industries, each with their own challenges and regulatory regimes and, as a result, technologies or solutions don’ t always transition between the two sectors as smoothly as one might hope or expect.”
As a result, Weir is collaborating with Schwing Stetter in Germany to share knowledge and, ultimately, it says provide the market with better solutions.
Schwing Stetter is a specialist OEM with a long history of designing and manufacturing hydraulic piston pumps for concrete pumping application. While Weir has mining expertise and experience in backfilling, as well as a range of pumps that have a proven track record of performing exceptionally well in what is one of the most arduous
International Mining | MARCH 2026 51