There are different types of rockbolts used in the mining industry but the basic form is an expansion shell anchor that is tapered into a cone at one end. A hole will be drilled prior to the rockbolt being used and it will then be inserted inside. You can tighten the bolt in order to increase the anchor force. 

Rockbolts are great for hard rock but this may not be feasible for soft or laminated rocks. Safety of workers and property in the mine are of paramount importance. Therefore, you need to carry out mine civil integrity testing to ascertain the quality of the rockbolt system. These professionals will also devise quality control and assurance solutions. You should be aware of all parameters in the mine that can affect the durability of the rockbolting system. In certain extreme conditions where there are high groundwater levels and high temperatures, rockbolts are increasingly at risk of corrosion. Corrosion of the rockbolt can cause it to fail but there are several methods that you can use to avoid this. For example, you can fill the gaps between the bolt and the hole with grout or resin. If there is groundwater present, then this is a precaution that should be taken.  You can achieve more reliable grouting when using a hollow core bolt.

When you are using mechanical rockbolts

These tend to become loose if subjected to vibrations resulting from nearby blasting. This can also happen if you have anchored the bolt in weak rock mass. To ensure that the support for the bolt is maintained, you can use resin anchors. Resin will set quicker than cement and you will be able to use this method for most types of rocks. You also need to consider the strength of rock mass that you are inserting the rockbolts. This will have a big impact on the durability of the rockbolts. If you have properly inserted a rockbolt into a high strength rock mass, it can maintain high performance for a very long time. You can achieve the same in a low strength rock mass but you will need to take additional strengths to ensure that support is maintained.

The materials you use for bolting and grouting also matter as the rockbolts will be performing under high stress. The quality of materials determines how well the loads are conducted along the length of the bolt. Mostly, steel is used for rockbolts. And when you are inserting a rockbolt at a greater depth in complex conditions, ribbed bolts are recommended as these provide improved adhesion over smooth bolts. The bolt will also bond more to the grout due to the ribbed texture. When it comes to pull loads, a rubbed bar will be more resistance compared to a smooth bar. But you have to consider the height and spacing of the ribs for maximum performance. There has to be a suitable space in between the ribs. In media with low rockburst, height can be maintained at a lower value.

Tags