The following is an article by Geobrugg which appeared in the Deep Mining 2024 Supplement.
Enhancing safety in deep mining: the evolution of dynamic ground support systems
by Geobrugg
As mining operations extend to unprecedented depths, the risk of rockburst – a sudden and violent release of built-up energy within the rock – becomes a growing concern. Rockbursts are significant hazards, particularly in underground mining, where depths often exceed 1,000 m, and even in shallower depths, the seismic activity resulting from excavation can lead to catastrophic consequences. The challenge of protecting both workers and infrastructure from these dynamic loads has led to the development of more advanced ground support systems, spearheaded by innovations in high-tensile steel wire mesh technology.
Traditional support systems, such as shotcrete reinforced with electro-welded mesh, have long been the standard in underground mining. However, these conventional methods exhibit limitations in handling dynamic loads. The increasing frequency and intensity of rockbursts have highlighted the need for more robust solutions. In response, the development of diamond-shaped, lightweight steel wire meshes, known as MINAX®, has revolutionised the approach to ground support in high-risk mining environments.
MINAX mesh, produced by the Swiss company Geobrugg, is a high-tensile steel wire mesh with exceptional strength and flexibility. The wire used in the mesh has a minimum tensile strength of 1,770 MPa, making it capable of absorbing significant energy while maintaining structural integrity. This innovation has been a game changer in underground mining, particularly in environments where static and dynamic stress levels are extreme.
The key to the success of these advanced support systems lies in the strength of the materials and the systematic research and rigorous testing that have accompanied their development. To fully understand and quantify the behaviour of these systems under dynamic conditions, Geobrugg established a state-of-the-art test facility in Walenstadt, Switzerland. This large-scale test centre allows for the simulation of real-world conditions, applying energies as high as 600 kJ to various ground support configurations.
The test rig, equipped with load cells, high-speed video analysis, and accelerometers, facilitates the detailed analysis of the response of different support systems, including the MINAX mesh combined with various bolt patterns.
The results were conclusive: the MINAX mesh provided superior energy absorption and maintained its structural performance, even under the most challenging conditions. The design’s flexibility allows it to distribute impact loads effectively across the mesh and anchors, reducing the concentration of stress at any single point and thereby enhancing the overall durability of the system.
The tests confirmed that the MINAX mesh, when combined with shotcrete and intentionally placed anchors, absorbs the high energy levels generated by rockbursts without compromising the integrity of the support system. This capability is crucial in preventing structural damage and reducing the need for maintenance, which, in turn, enhances the safety and productivity of mining operations.
Not only have these tests validated the effectiveness of the MINAX mesh, but they have also provided valuable insight into the behaviour of various ground support systems under dynamic loading. The large-scale tests in Walenstadt demonstrated the importance of combining high-tensile steel wire mesh with a well-thought-out bolt pattern. The ability of the mesh to absorb and dissipate energy is significantly influenced by the arrangement and strength of the bolts, as well as the system’s overall flexibility. These findings underscore the need for a holistic approach to ground support design, where each component works synergistically to maximise the system’s energy absorption capacity.
Beyond the technical achievements, the success of the MINAX mesh in real-world applications has profound implications for the future of deep mining. As mines continue to reach greater depths, the frequency and severity of seismic events are likely to increase, necessitating even more resilient ground support systems. The ongoing research and development in this field, exemplified by the collaboration between Geobrugg and various leading mining companies, pave the way for safer and more efficient mining operations worldwide.
Adopting these advanced ground support systems also addresses the economic aspects of mining. By reducing the need for rehabilitation caused by rockburst damage, mines can operate more continuously, minimising downtime and maximising productivity. Furthermore, the enhanced safety these systems provide ensures that miners can work in environments that, despite being increasingly hazardous, are made safer through cutting-edge engineering solutions.
Impact point after test. The surface support system remains largely intact with no mesh failure
The success of these initiatives highlights a significant shift in the mining industry’s approach to ground support. No longer relying solely on traditional methods, mines increasingly turn to innovative materials and designs to meet the demands of deeper and more dangerous operations. The MINAX mesh, with its high tensile strength and flexibility, represents a crucial advancement in this evolution, offering a proven solution to one of the most pressing challenges in modern mining.
In conclusion, as the mining industry continues to push the boundaries of what is technically feasible, the need for advanced ground support systems will only grow. The development and testing of high-tensile steel wire meshes have provided the industry with a powerful tool to combat the risks associated with deep underground excavations. With these advancements, the industry is better equipped to face future challenges, ensuring that as mining goes deeper, it does so more safely and sustainably.
