Over the past few decades, mining engineering and tunnel construction have faced increasingly complex geological environments. Traditional rock bolt technology often cannot effectively solve the reinforcement problem of surrounding rock, which has prompted engineers to look for new solutions. The split set was born under this background. It quickly gained recognition from engineers with its unique design and excellent performance.
TRM supply professional and honest service.
Split set is a new type anchor of full-length anchoring and active reinforcement of surrounding rock. It has been widely used around the world. It mainly consists of two parts: a high-strength anchor rod and a tray. The surface of the anchor rod has longitudinal slits, which allows it to better adapt to the shape and size of the surrounding rock when installed. When the rock bolt is embedded in the borehole, these gaps can generate friction, thus exerting internal radial pressure on the surrounding rock. In addition, the anchor tray also plays a key role, preventing the surrounding rock from sliding down while providing additional support.
The split set is a high-strength anchor rod with longitudinal slits. When installed in a borehole slightly smaller than the pipe diameter, it can immediately exert radial pressure on the hole wall throughout the entire length and prevent the surrounding rock from sliding over its whole length, together with the supporting force of the anchor tray, which puts the surrounding rock in a state of three-directional stress and realizes the stabilization of the rock stratum. In the case of blasting vibration and surrounding rock movement, there is a significant increase in the later anchoring force. When the surrounding rock is significantly displaced, the rock bolt does not lose its support resistance.
High performance: the friction between the anchor rod and the rock mass is high, and it has high shear and tensile strength; the drilling depth is greater than the depth of the rock bolt, and it can provide timely support in the radial and axial directions. It is not suitable for permanent support in soft rock.
The emergence of split sets has changed people's understanding of geotechnical reinforcement and provided us with new ideas and methods for solving engineering problems with various complex geological conditions. Nowadays, split sets play a significant role in mining projects. We have reason to believe that by further researching and improving the technical parameters and design methods of split sets, we can better play its role in geotechnical engineering and provide a strong guarantee for project construction.
The geo-tech engineer will set the broad requirements for each type of cut and the standard will be upheld by the foreman and the shift bosses. As the geo-tech if you get asked to look at something then go as soon as you can and if you are not sure then ask the shift boss for their views, they will help you out.
After rattling down the loose rocks with the jumbo, the ground support will be installed. Ground support consists of rock bolts, mesh and, or shotcrete. Using a combination of the 3, underground mines manage the different ground conditions encountered in the mine. There are 3 types of bolts that are used in an underground mine, these are Split Sets, Chemical Bolts and Cable Bolts.
Split Set bolts come in different lengths (1m, 1.8m, 3m), are round with a strip of metal missing up the side. They are tapered at one end, with a full ring at the other, which holds a metal plate about 30cm x 20cm, all have the same diameter (around 60mm).
The bolt with plate is loaded onto the jumbo boom then pushed into a predrilled hole, the bolt works by squishing the metal into the smaller diameter hole (no bigger than 43mm) and holds about 3 ton of ground.
The rows are installed 1.5 metres apart and go all the way to the end of the drive. If there are no bolts in place then this is classed as unsupported ground, never ever go under unsupported ground for any reason.
Are you interested in learning more about Split Sets Underground Mining? Contact us today to secure an expert consultation!
Mesh is used against the rock to hold smaller rocks in place and hold areas of subsidence. The idea is that if something falls then the mesh will catch it only letting the smallest of rocks through. Mesh is pinned to the backs (roof) using the bolts to pin the mesh in place. This work is carried out by a twin boom Jumbo.
Shotcrete is used to reduce the chances of any rock falling, it does this by covering the exposed rock with a mixture of concrete, small plastic covered strips of metal and chemicals to speed up setting time. This forms shotcrete and is sprayed on to a thickness of 50mm. Once set, this forms a protective shell that is then bolted. You can see examples of shotcrete on roadways and in tunnels.
Did you spot the safety problems? That’s right he’s not wearing gloves or glasses. Please make sure you wear your PPE.
Chemical bolts use a cartridge of chemical placed into the pre-drilled hole, then the jumbo loads the correct bolt with a plate that is then pushed into the pre-drilled hole, once set (normally takes 45 seconds to a minute) a locking nut is used to tighten it to the backs.
The bolt is solid and spiralled like a masonry bit to mix the chemical as the bolt is installed.
These bolts are classed as long term ground support and hold up to 7 tonnes of ground per bolt, these bolts are mainly used in the decline.
A cable bolt is stranded steel wire that is fed into a pre-drilled hole that can be up to 30m or more long. This is done using either single or multiple stranded cables that are then secured into place with grout and left to set for 12 hours
After this time the cable can be plated and tensioned. These are the same bolts that are used to anchor open pit walls, high rise buildings to the ground and hold up the hillsides that motorways are cut through. In an underground mine they are used in spans larger than 6m such as intersections as the bolting plan below shows. Cable bolts can hold in excess of 20 tonnes.
The above picture is an intersection or X cut as the miners call it. Each blue dot represents a cable bolt so if the cable bolts are 8m long each the cable bolts are holding up 160 ton. The deeper we go into the earth, the more levels we go down and it is for this reason that the industry uses a numbering system that is determined on the meterage above or below sea level. The distance between levels will be around 20m, so as you go down the decline the levels will be numbered 780, 760, 740, 720 and so on.
Contact us to discuss your requirements of Friction Bolt. Our experienced sales team can help you identify the options that best suit your needs.