SELF DRILLING ANCHORS
A self-drilling anchor is a type of bolt used to ensure the stability of the roof and walls in underground mining and tunnel construction. Unlike other types of bolts, self-drilling bolts do not require pre-drilling and can drill and hold at the same time. These bolts are designed with a hollow threaded bar with a one-time use drill bit at its end, simplifying and reducing the installation process. Once installed, they are filled with resin or cement mortar to consolidate the ground. In addition, these bolts can be joined by couplings to achieve lengths that would be impossible with other types of bolts. At the end of the bolt, there is a nut that, once installed, is tightened, putting the bearing plate and the bolt itself under load, further increasing the bolt’s effectiveness. Self-drilling anchors can also be used in areas where the rock is harder or more compact, using different types of bits. By drilling and securing at the same time, the need for additional equipment for pre-drilling is reduced, which also reduces cost and installation time.
FIELD OF APPLICATIONS
Self-drilling bolts have a wide variety of mining and tunneling applications, such as:
*Rock support: Self-drilling bolts are used in mining and tunnels to provide support and stabilization of rocks.
*Anchor systems: Self-drilling bolts are used to fasten and secure structural elements such as tunnels, mine roofs, pillars, etc. into rock or soil.
*Rock repair: Self-drilling bolts are also used for the repair of damaged or weakened rocks and soils in mines or tunnels.
*Equipment assembly: Self-drilling bolts are used for fastening equipment, machinery, and other elements in mining and tunnels, such as lights, fans, conveyor belts, etc.
FEATURES
Hollow anchors rods
They are manufactured from API cold rolled standard thick wall steel pipes to a standard ISO thread profile. The rolling process increase the yield strength and produces a durable drill rod. They are hollow bars for subsequent grouting or resin insertion. 2, 3, 4 and 6 meters length
Couplers
To join different anchor rods, it is designed to enables end to-end energy transmission between each bar. To enable the correct seating of each barr within the coupler all ONIX bars are chamfered with precision to enable the bar ends to have face-to-face contact
Single-use drill bit
The sacrificial drill bits drill as the bolt advances.
Different types depending on the ground where they will be used:
*EX: Hardened cross bit loose to medium dense ground
*ES: Hardened button bit for unconsolidated rock with boulders *EXX: TC cross bit for soft to medium rock formations
*ESS: TC button bit for medium rock formations
Hardware
Nuts and washers to be used with the anchor bar.
TYPE R
Type R self-drilling anchors have an excellent internal and external quality control. The R-type thread is in accordance with ISO10208, ISO 1820 (R51) and the internal hollow of the bars guarantees compliance with EN14199/EN14490/ASTMF432/ASTM A615 standards. Specialsizes are available on request as well as galvanizedorcoatedcomponents.
TYPE T
Type R self-drilling anchors have an excellent internal and external quality control. The R-type thread is in accordance with ISO10208, ISO 1820 (R51) and the internal hollow of the bars guarantees compliance with EN14199/EN14490/ASTMF432/ASTM A615 standards.
ADVANTAGES
*Fast installation: Self-drilling bolts are easy and quick to install. They can be drilled and anchored in a single operation, which reduces installation time compared to other anchoring systems.
*Less need for equipment: Self-drilling bolts do not require special drilling equipment, which means that the number of equipment and the cost associated with drilling the anchors can be reduced.
*High strength: They are extremely strong bolts and can withstand large loads. This makes them ideal for use in the mining and tunneling industry, where strong and resistant anchors are required.
*Flexibility: since they can be installed in a variety of materials, including hard rock, soil, and concrete. Additionally, they can be used in different geotechnical conditions, such as unstable terrains or presence of water.
*Safety: Self-drilling bolts are safe and reliable. Being designed to install correctly, they minimize the possibility of human errors in the installation and reduce the risk of structural failures.
INSTALLATION
1) Preparation: before beginning the installation of self-drilling bolts, it is important to prepare the installation site. This may include cleaning and clearing the work area, removing any loose or unstable material, and assessing the local geology to determine the optimal location for bolt installation.
2) Drilling of pilot hole: the first step is to drill a pilot hole in the rock or soil using a tungsten carbide drill bit. The diameter of the hole should be slightly smaller than the diameter of the self-drilling bolt for a good grip to occur.
3) Installation: once the pilot hole has been drilled, the self-drilling bolt is inserted into the hole and rotated into place. The self-drilling bolt’s bar has a drill bit on the end, and as it is rotated, the bolt’s bar drills into the rock or soil and secures it in place.
4) Grout injection: after installing the self-drilling bolt, grout is injected through the bolt’s bar to fill the space between the bolt and the surrounding rock or soil. The grout helps to provide additional anchorage for the bolt and protects against corrosion.
5) Bolt anchoring: to anchor the bolt in place, a tension load is applied to the bolt through a locking nut or coupling. This will ensure that the bolt is firmly anchored in place and can support the loads for which it has been designed.
6) Installation inspection: after the self-drilling bolt installation, an inspection should be carried out to ensure that it has been installed correctly and that design and load requirements have been met. This may include load testing and visual verification of the bolt and surrounding area.