Rockfall is one of the leading causes of accidents in underground operations. Occasionally, during the development of a gallery, the terrain presents characteristics that allow us to infer the need for preventive fortification systems, such as resin injection before advancing, to prevent possible rockfalls.
However, when the rockfall couldn’t be prevented, it is necessary to implement safe gallery recovery systems to avoid further dangerous situations. For these scenarios, Weber Mining & Tunnelling says it has developed the latest technologies in expansive resins, allowing cavities to be filled safely and quickly without exposing mining staff.
The company told IM: “After a rockfall, two possible situations arise. The rockfall occurred, and the cavity is stable. In this case, a safe recovery consists of projecting shotcrete onto the cavity walls and placing steel frames onto which the expansive resin will be applied. The resin is injected from outside the collapse zone through an injection lance that reaches the cavity via an opening left when placing the frames. Once the injection begins, the resin expands to 40 times its initial volume in two minutes. Weber Mining & Tunnelling’s injection pump allows up to 80 m3 to be injected per hour, ensuring a quick filling of large cavities.”
It adds: “As the cavity fills, the resin exerts positive pressure against the walls, stabilising the ground. The cavity is considered completely filled once the pressure gauges of the injection pump increase, showing no more empty space. Thanks to this technology, even if the cavity is 20 m high, it can be filled without exposing any worker to risks in just a few hours. As a flexible product, the expansive resin evenly distributes ground movements onto the frames, optimizing the resistance of support systems in the event of further ground movements.”
On other occasions, rockfall might be ongoing, preventing the application of shotcrete or the placement of steel frames. In these cases, the expansive resin can be injected from the gallery floor, keeping personnel out of the risk zone. “Given the expansive capacity of the resin, when injected from the floor, it will fill the cavity up to the gallery ceiling. Once the cavity is filled, the recovery process involves placing frames starting 4 m before the rockfall zone, then gradually excavating inside the expansive resin and fallen rocks. In this way, excavation is safe as progress is made under a ceiling of expansive resin and ground support.”
Weber Mining & Tunnelling says its latest technologies in expansive resins have facilitated the recovery of collapsed galleries without endangering mining staff, optimising rehabilitation processes, and contributing to the safety of their client’s operations.
