As underground mining contractor Murray & Roberts Cementation and its client, copper miner Palabora Mining Company (PMC) continue their journey towards the 1 200-m mark in the construction of the ventilation shaft for the PMC Lift II expansion project, innovation and safety have taken centre stage. This sets new standards for the mining industry and underlines their commitment to employees and the future of mining in the region.

The PMC project involves innovative approaches to the ventilation shaft construction such as using specialised concrete mixes and prioritising safety.

The innovative use of specialised concrete mixes, tailored to meet the unique needs of the ventilation shaft construction, has been a noteworthy aspect of the project, says Murray & Roberts Cementation senior project manager Fred Durand.

These concrete mixtures are more than just building materials – they are a critical component of the project’s success.

“To ensure the correct mix, workability and setting requirements, admixtures are carefully administered during the batching process. The curb ring concrete, for instance, incorporates an accelerator admixture, while the filler ring benefits from an extra super-plasticiser. These admixtures play a crucial role in promoting early strength, accelerating curing and aiding the flow of the concrete from the shaft slickline to the formwork,” he explains.

It is essential that the concrete mix flows into position easily, preventing any uneven build-up inside the shaft shutter. Samples from each batch are rigorously tested for slump, ensuring adherence to South African National Standards. The curb mix boasts a rapid setting, with a strength of 3 MPa within just four hours and an ultimate curing strength of at least 30 MPa.

These innovative approaches, including the tailored concrete mixes, have far-reaching implications for the future of shaft sinking projects in the mining industry.

“Safety and innovation input from the ground level upwards has taken precedence over other considerations, leading to favourable changes in shaft sinking cycles and a more streamlined and secure process,” states PMC senior manager concentrator for underground construction and vent shaft Aidan Schoonbee.

“By eliminating concurrent work in the shaft bottom during work on the stage, the risk of objects falling on people has been virtually eradicated. This approach permits a smaller multi-skilled crew of workers in the shaft, and the same team responsible for extending services and shaft lining also manages the lashing of the shaft bottom, blow over, drilling and blasting. This organised and compartmentalised approach ensures safety and efficiency,” he explains.

During lashing cycles, only the excavator driver is present in the shaft bottom, eliminating the need to offload a kibble in the shaft bottom. The full kibble in the headgear is safely clutched out and tipped, reducing the risk associated with traditional methods.

“The project’s success showcases that shaft sinking projects can be executed with less risk, given that inline activities in the sinking cycles might take longer. Project schedules can be more realistic by basing them on actual achievements from similar completed projects,” says Durand.

The collaboration between PMC and Murray & Roberts Cementation prioritised safety at every turn and their unwavering commitment to safety has been a cornerstone of the project’s success.

“Safety systems and protocols have been implemented from top to bottom and from bottom to top. Multiple safety campaigns and continuous collaboration with PMC safety professionals have ensured that safety is integrated into every step of the process, from meetings to ‘take fives’, line-ups and toolbox talks,” Durand elaborates.

Meanwhile, safety resources from PMC and Murray & Roberts Cementation have been assigned to the project to oversee and manage safety procedures, further enhancing the fatality-free record. The efforts have paid off, with Murray & Roberts Cementation celebrating seven-million fatality-free shifts in September 2023, a remarkable milestone that underscores the team’s dedication to daily safe production.

The PMC ventilation shaft project is a testament to this commitment, boasting an impressive fatality-free record and contributing to the broader achievement of safety in mining.

Adapted Methods

The PMC project is loosely based on a Canadian shaft sinking method, but has been adapted to suit the unique conditions at PMC, which further enhances safety. A significant departure from the traditional Canadian approach involves a 3-m-high hydraulic activated shaft shutter, which is lowered during the shaft bottom lashing process.

This innovative method decreases exposed and unsupported shaft sidewalls of more than 1.5 m, reducing the risk to workers who would traditionally be exposed to unsupported sidewalls during lashing and standing beside them. The shutter, serving as temporary support, is filled with concrete and acts as a buffer for the crew’s safety.

The decision to carry the permanent concrete lining to 1.5 m within the face eliminates the need for temporary support and removes the risk to workers in the shaft bottom during drilling and support cycles.

Durand notes that the PMC Lift II ventilation shaft project is a testament to how innovation and a deep commitment to safety can redefine the future of mining.

“Tailored concrete mixes, streamlined processes and adapted methods not only contribute to a successful project but also set new benchmarks for the mining industry. As the project progresses, we look forward to the changing mining landscape in Phalaborwa, which looks brighter, safer and more efficient than ever,” he concludes.