Rock bolt is the most widely used support element in support systems in underground mines and civil tunnels. Rockb olting design is indeed mainly based on experience and it appears that rock bolting design is simply a business of selection of rockbolt types and the determination of bolt length and spacing, but, one essentially uses, either explicitly or implicitly, a methodology in a specific rock bolting design.
The suitable types of rock bolts for a given rock mass are associated with the loading condition in the rock mass. In the case of a load controlled condition as shown in Fig. 1, the strength of the rock bolts is the most important parameter for the selection of rock bolt type. The basic requirement is that the strength of the rock bolts must be higher than the load on the bolts. The appropriate types of rock bolts under load controlled conditions are fully encapsulated rebar bolts, thread bar bolts and cable bolts.
In over stressed weak and soft rock, the excessive deformation needs to be accommodated. The traditional approach to deal with rock squeezing is to use ductile rock bolts in conjunction with other types of ductile surface retaining elements such as mesh. Split set is the typical rock bolt for this purpose in the mining industry. Split set can displace significantly, but it cannot much restrain the rock deformation because of its low load-bearing capacity.
Its main function is to avoid disintegration of the fractured rock mass. An active measure to stabilise squeezing rock is to provide a high support resistance to restrain the rock deformation on the one hand, while the support elements in the support system must be deformable on the other hand. Use of energy-absorbing rock bolts can achieve this goal.
Rock burst is an instability issue in overstressed hard and strong rock. The goal of rock support in such conditions is to absorb the kinetic energy of the ejected rock. Energy-absorbing rock bolts should be used in burst prone rock masses. The higher the load-bearing capacity of the energy absorbing rock bolt is, the less the ejected rock displaces.
Various sizes of self drilling rock bolts from Sinorock can provided for you,Sinorock self drilling rock anchors are often used for excavation support, or as a part of permanent retaining walls, or to resist up-lift forces on foundations. Sinorock uses rock anchors to stabilize slopes and walls, provide tiebacks for bridges, stabilize dams, and secure caisson bottoms.