Backfilling is the process of refilling an excavated hole.
Backfilling in underground mines is a fundamental part of the operation. The backfill material provides support to the surrounding rock mass, mitigates the risk of surface level subsidence, reduces wasteful ore dilution, and creates a safer working area for mining activities. Using mining backfill can also be a way to dispose of potentially hazardous waste and reduce the environmental impact on the surface by storing backfill waste underground(Essential Guide to Backfilling in Mining Operations, n.d.).
Backfill typically contains waste materials left over after the target mineral is extracted, which is commonly referred to as tailings.
The following materials are commonly used to backfill mines:
- Cemented backfilling. Cement is poured over tailings and waste rock to help fill voids that need filling, thus binding the backfill together. This is particularly useful when low volumes of cement are needed to bind materials since cement can be very expensive in large quantities.
- Dry rock backfilling. Dry rock consists of dried tailings, gravel, rock waste, or surface sand. This backfilling material is best used in cut and fill mining.
- Hydraulic sand backfilling. Hydraulic sand is the result of separating out fine sand from tailings and using the coarser sand as backfill. The sands are hydraulically pumped into voids in mines. When deemed necessary, the sand can be mixed with binding agents.
- Paste backfilling. Paste backfill is typically used in coal mines. Solid tailings are broken down and mixed with water, cementing materials, and fly ash, creating a coagulable paste that can be used for backfilling.
What other material could be used for backfilling in mining? Comment below!
