Self Drilling Rock Bolt (SDRB) system provides higher tensile strength than conventional solid bolts

Self drilling rock bolt can be used for permanent support project in medium and good rock condition and foundation support. By doing pressure grouting, it can help to reinforce the broken rock mass, improve the rock mass and prevent the corrosion from underground water and then reach the purpose of supporting.
Self-Drilling rock bolt is used to attach objects or structures to concrete. There are many types of Self-Drilling rock bolts, consisting of designs that are mostly proprietary to the manufacturing companies. All consist of a threaded end, to which a nut and washer can be attached for the external load.
A new Self Drilling Rock Bolt (SDRB) system has been developed which uses a pumpable resin system for full column resin encapsulation for immediate roof and rib support. A new drilling and injection system has also been developed to enable fast and efficient bolt installation.
This new SDRB provides higher tensile strength than conventional solid bolts, and also provides a load transfer capacity that is almost double that of conventional bolts. This new SDRB uses low viscosity pumpable resin to ensure full encapsulation right down to the collar.

This not only provides a high load transfer capacity over the entire
length of the bolt, but also reduces the potential for bolt corrosion and locks the bearing plate and mesh in place at the borehole collar.

It will also reduce the amount of water inflow from the roof in mines which have water problems. The advantages of this alone are considerable.
The installation system is also new and consists of a new drill chuck and resin pump which can be retro-fitted onto a continuous miner.

Production versions of the installation system can have full PLC control to further refine bolt installation to have full semi-automatic bolt installation. In addition, resin cure times can be adjusted to suit mine roof conditions such that the resin cure time coincides with full resin encapsulation of the bolt to further reduce installation cycle time.
The current SDRB installation cycle has not yet been fully optimised, and further reductions in bolt cycle time are possible. Nevertheless, the current SDRB installation cycle times for a 2m long bolt are typically 60 seconds,  compared to 150 seconds for a conventional bolt in the same roof.
The full benefits of SDRB technology to the coal industry will only be obtained if these bolts are installed at the face. In the immediate future, this requires retro-fitting the SDRB equipment onto existing continuous miners, and some miners are better suited to this application than others.
This new SDRB uses semi-automatic bolt installation with manual placement of the bolt into the drill chuck, which greatly simplifies the whole installation process. Although a longer term goal would obviously be to have full bolting automation, with bolt handling into the drill chuck to remove operators from unsupported roof. Consideration needs to be given not just to the bolting process itself, but also to the materials re-supply to the machine. This will be essential if high roadway drivage rates are to be achieved.
Longer term the coal industry should encourage machine manufacturers to design and produce machines that are better suited to SDRBs and to full bolting automation.

The length of self drilling anchor affects the grouting self drilling anchors

Since the total length of grouting self drilling anchors with safe and reliable, simple construction and low cost, they are widely used in slope engineering. When self drilling anchors reinforced slope, depending on the interaction between surrounding rock mass and self drilling anchor transmitting rod tension, making themselves get reinforced in geotechnical engineering, limiting the deformation, and improving stress state of the mechanical parameters of rock mass and to maintain stability. Due to the self drilling anchors load transfer mechanism is very complicated, so far still assumes that the lateral resistance distribution patterns in self drilling anchors  design is uniform distribution.

But a large number of measured results show that it is unreasonable according to uniform distribution pattern calculated. In recent years, with the development of computer technology, numerical simulation methods are widely used in geotechnical engineering, adopting double spring self drilling anchor element, the establishment of a model of Highway slope was simulated excavation process of the rock bolts reinforcement effect.
While the combination of the long self drilling anchor and the short self drilling anchor can foster strengths and circumvent weaknesses. The supporting effect is definitely better.


In the combining support of the long self drilling anchor and short self drilling anchor, the former on one hand controls the deformation of
surrounding rock except the reinforced composite arch. On the other hand, it can reinforce the combination arch structure to hang on the stable rock for coordinate deformation of surrounding rock.

Relating to the short self drilling anchor, it can reduce the hulking deformation of the rock and the further damage of the fracture by limiting the deformation of the near area and the development of the fracture surface. The short self drilling anchor can also form reinforced composite arch structure which has a certain bearing capacity near tunnel surrounding rock. All these can strengthen the integrity and stability of the surrounding rock effectively.
http://www.neighbour123.com/blog/show/coal-roadway-rock-bolt-design-technology-of-sinorock