GROUND SUPPORT
Geobrugg full-scale test rigs in Walenstadt , Switzerland
Support and training with virtual reality simulators . The customers are some of the major Chuquicamata contractors – Geovita , Grupo CBB and the Acciona-OSSA-Pizzarotti and OSSA- Pizzarotti consortiums .
More recently , Codelco has confirmed that it is now using an all electric Normet SmartDrive Utimec MF 500 Transmixer which Normet says provides the highest productivity on its size class . It has “ a large concrete transport capacity and extremely high output power to ensure high tramming speed also when it is fully loaded .” The new Chuqui unit is operated by Grupo CBB . Codelco says it offers an 80 % reduction in energy costs , 30 % reduction in maintenance costs and 95 % availability .
Superior ground support with MINAX ®
Mining is getting deeper , and rockbursts are a growing risk in underground excavations around the world . Especially in mining tunnels , when in search of new ore horizons , tunnels are getting deeper and reaching depths greater than 1,000 m and more . However , seismicity events and associated rockbursts can occur even at lower depths . Traditional support and reinforcement systems such as shotcrete reinforced with electro-welded mesh or fibercrete used in underground mining are limited in their capability against dynamic loads . The development of diamond-shaped lightweight MINAX ® steel wire meshes of very high strength in recent years has offered alternative design solutions . In order to fully understand the behaviour and capacity of various ground support systems using these MINAX ® meshes , the Swiss company Geobrugg has carried out many full-scale dynamic tests in its own test centre in collaboration with universities and mines from all parts of the world . The need to increase the energy dissipation capacity in the support system designs of different mines has been present for many years . With this goal in mind , systematic studies have been carried out , aiming to improve the performance of both the single elements and the complete reinforcement systems . In addition , the development of diamond shaped lightweight steel wire membranes of very high-tensile strength , in recent years , has given a great boost to this trend . These powerful flexible solutions combined with suitable anchors have undoubtedly been a huge step towards solving situations where protection against dynamic load is imperative .
In order to prove the suitability of such support systems with high-tensile steel mesh and bolts and to analyse the bearing behaviour of them , a large-scale test centre was commissioned in Walenstadt , Switzerland . On a test rig it is possible to apply large energies on variable ground support systems with variable bolt patterns and meshes with a total support area of 3.6 m x 3.6 m in a full-scale way . The test site is instrumented by load cells , high-speed video analysis and accelerometers . It could be shown that a combination of high-tensile steel mesh with a specific bolt pattern can result in high energy capacity surface support . Distribution of the impact loads during the stopping process to the different elements of the bearing support system depends on the strength
ThingWave : rockbolt mass monitoring
ThingWave ' s Digitalized Ground Support ( DGS ) technology provides mass-monitoring
and flexibility of the mesh and the bolt resistance and its pattern . Given the characteristics of a structure that attempts to reproduce the conditions of a mine , boundary conditions are generated , which do not allow a direct correlation of the results obtained in the test with the results expected at the mine . However , it allows comparisons between systems / elements of fortification and helps to advance understanding of the complex problem of ground support .
The new ground support designs , developed over the last few years , consist of hightensile MINAX ® steel wire mesh , anchors and shotcrete . Because of the use of high-tensile steel wire ( min 1,770 MPa ) and the flexibility of the chain-link mesh , such a support system can be applied in areas with very high static and dynamic stress . On several rockburst occasions worldwide , it was clearly demonstrated that this type of design , with MINAX ® , allows high energy absorption of the dynamic loads from periodic rockbursts , depending of the magnitude of the incident usually without any maintenance requirements , which is both fundamental for guaranteeing miners ’ safety and essential to increase the productivity of mining development ultimately . With this successful test series of a reinforcement system ( shotcrete with mesh , bolt and a second mesh with cable bolts ) under dynamic conditions , Geoburgg states : “ We can add experimental antecedents to the theory and confirm that this type of support is with no doubt a huge step forward in increasing the safety in underground mining .” IM of rock bolts by the use of wireless sensors using mesh networks and 5G . Its platform can be integrated with different types of rock bolts and can send status information about elongation , strain , breakage , and seismicity to its gateway using a state of the art wireless mesh network . The system has been field-tested at active mines and delivers realtime monitoring with up to ten years of a lifetime for each bolt . But the company continues to deliver new solutions to ground support issues . Fall of ground events are a major cause of injuries and production losses in underground mining . ThingWave is therefore working on a solution for detecting even minor events such as small rocks that fall . Its IoT devices transmit data to its AI software for analytics and classification of events . From ThingWave Cloud , it can send out alarms to staff on-site to take action . ThingWave ' s newest development is a Wi-Fi-based wireless sensor node capable of sensing vibrations at several kHz . It can send the vibration data over MQTT both to ThingWave Cloud and Eclipse Arrowhead . This can be used for condition monitoring , OEE and predictive maintenance .
76 International Mining | AUGUST 2021