Self drilling anchors are special type of rod anchors. Self-drilling anchor consists of a sacrificial drill bit, hollow steel bar of the appropriate outer and inner diameter and coupling nuts.
The anchor body is made of a hollow steel tube with an outer round thread. Steel tube has the sacrificial drill bit at one end and the corresponding nut with a steel end plate.
Self drilling anchors are used in a way that hollow steel bar (rod) has a corresponding sacrificial drill bit on its top instead of a classic drill bit.
Centralisers guarantee a consistent grout cover around the hollow steel bar and that the bar remains in the center of the drilled hole.
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Construction of self drilling anchor
Anchor hollow steel bars are produced in sections with standard lengths of 2.0, 3.0 or 4.0 m. The standard outer diameter of the hollow steel bars ranges from 30.0 mm to 127.0 mm.
If necessary, hollow steel bars are continued with coupling nuts. Different types of sacrificial drill bits are used depending on the type of soil or rock mass. A hollow steel bar is better than a solid bar with the same cross-sectional area because of its better structural behavior in terms of buckling, circumference (bond area) and bending stiffness. The result is a higher buckling and flexural stability for the same amount of steel (cost of material).
Hollow steel bars
In the case of special durability requirements and more aggressive soils, hollow steel bars could be corrosion protected by hot-dip galvanizing or its material could be stainless steel.
Self drilling anchor cross section
The hollow steel bar is driven to the required depth by means of rotary percussive drilling. Injection is carried out through hollow steel bar. Injection mixture flows through the holes at the sacrificial drill bit and automatically stabilizes the drilled hole. Injection ends when the mixture begins to exit from drilled hole. The cement grout is most often used for injection of self-drilling anchor. The usual water-cement ratio ranges from 0,40 to 0,50.
Anchor grouting
Installation of self drilling anchors
The basic application of self drilling anchors is installation under the conditions of the soil/rock with the risk of drill hole collapse due to pulling out of drill bit as in the classical anchor installation process.
Self drilling anchors can be installed in length greater than classic rod anchors (joining of a hollow steel bar with coupling nuts).
Range of applications:
&#; micropiles for foundation underpinning (anchors with larger diameter)
&#; anchors against uplift
&#; anchors for protection of rock slopes and building pits
&#; anchors for stabilization of soil slopes (soil nailing)
&#; anchors for stabilization of embankments
&#; anchors for protection of retaining structures
&#; drains (drainage of water)
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Installation of self drilling anchors depending on the diameter of anchors used, installation conditions, material quality and anti-corrosion protection ranges from 250,0 to 350,0 kn per m&#; of an anchor.
Self drilling anchor system is a type of ground anchor used to provide stability in soil or rock formations. The system typically consists of a hollow anchor bar with a drill bit on one end and a coupling on the other. During installation, the drill bit is used to bore a hole into the ground while simultaneously injecting grout into the hole to fill any voids. The anchor bar is then inserted into the hole and the grout is allowed to set, creating a bond between the anchor and the surrounding ground. This creates a stable foundation that can support a variety of structures and engineering projects. Self drilling anchor systems are commonly used in construction, mining, and tunneling applications.
ADVANTAGES OF SELF DRILLING SYSTEM
Features of our self-drilling anchor system include quick installation through combining drilling, insertion, and grouting in a single operation, along with low-noise percussion drilling. The system eliminates the need for separate installations and casing/rod removal, as the drill bit remains in the ground as a spacer. Different drill bits are available for diverse ground conditions, and the same installation principle applies to all systems and ground conditions. Our hollow core anchor rod also flushes the borehole with air/water during drilling, grouts voids, and carries out high-pressure injections in the annular space. We offer a variety of high-quality grouts and mixers, and our couplers provide flexibility in length. Our system is compatible with small drill rigs and narrow spaces. We also provide enhanced corrosion protection and maintain a high standard of quality assurance throughout the production and installation of our injection anchors/piles.
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