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The self-drilling anchor bolt system is composed of a hollow anchor bar, coupler, nut, drill bit, plate, and centralizer. It can combine drilling, grouting, and anchoring in one process. The self-drilling anchor bolt system is safe, efficient, and convenient. It is suitable for broken rock, loose soil, and geological conditions where is difficult to drill holes. It helps to ensure the anchoring effect in complex ground conditions and achieve the best construction result.
It is an advanced anchoring system that can directly realize drilling and grouting functions in loose soil layers and broken rock layers, consisting of a continuous full-threaded hollow bolt body, a sacrificial drill bit, a coupler, a flat or domed plate, a hex or domed nut, a centralizer, and other accessories. Self-drilling anchor systems can be used as micro piles and soil nails and are a fast and efficient solution for geotechnical anchoring.
Thread Processing Methods
The thread shape of the hollow bolt body is very similar to the thread of the steel rib. The thread pitch is large and the teeth are deep. The surface thread of the connection can not only bond with the cement, but also provide good adhesion and friction resistance, and can be extended at will.
The external thread of the hollow bolt body needs to be processed by a three-axis thread rolling machine. Because the raw material is a hollow steel pipe, the two-axis rolling machine is prone to the problems of oval, flattening, and even cracking of the hollow bolt body. Therefore, a three-axis thread rolling machine is used. The processing thread has good forming and high precision, which can meet the needs of drilling construction.
Thread Types
There are two kinds of threads on the surface of the hollow bolt body, one is the R-type thread that conforms to the ISO standard, and the other is the T-type thread that can provide greater support force. Generally, the adhesion friction force of the same type of T-thread is more than twice that of the R-type, and the T-thread anchor is more used in the application of micro piles.
Two methods are used to process the hollow bolt body, cold rolling, and temperature-controlled rolling. Cold-rolled threads are rolled to improve the grain structure of the steel and increase the yield strength. The temperature-controlled rolling can be changed according to the different needs of the application scenarios. The mechanical properties of the hollow bolt body and temperature-controlled rolling can more effectively ensure the metallographic structure and finer grains of the rod body. It is suitable for occasions with high elongation requirements and meets more customer needs.
Features and Advantages
1. Self-drilling anchor bolt system, which combines drilling, grouting, and anchoring together, is suitable for broken rock and conditions which are difficult to drill holes. Casing pipe is omitted in construction, which greatly improves construction efficiency.
2. Self-drilling anchor bolt system has a rich variety of drill bits, and the drill bit can be selected according to the properties of rock and soil, which can improve the drilling efficiency.
3. Self-drilling anchor bolt system can fill cracks, consolidate rock mass and soil layer through pressure grouting, and has good grouting spreading radius and reliable anchoring quality.
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4. The hollow anchor bar can be cut arbitrarily and lengthened by the coupler. Therefore, the self-drilling anchor bolt is suitable for construction in a narrow space that large equipment cannot enter.
Tunneling in Rock, Underground Structures
self drilling rock bolts, self drilling rock anchors
Self drilling anchor bar is mainly used in tunneling pre-support, which is widely used in mining, tunneling, railway, metro tunnel projects. R32 self drilling anchor takes a significant place in R-thread types for it&#;s superior reliability and extensive application in railway system and metro tunnel project. Under the condition of broken rock, weathered rock, loose soil, sediment layer and complex formations which are difficult to drill holes, self drilling anchor bar can efficiently support and improve the surrounding rock and achieve an ideal supporting effect when used for pre-support and radial support in the metro tunnel.
Construction Advantages of Self Drilling Anchor Bar
Because of special structures of self drilling anchor bar, there are several advantages during anchoring construction:
1. High efficiency of construction. Self drilling anchor bar combines drilling, grouting and anchoring together, with saving time and
labor force.
2. Suitable for stratum which is difficult for pore-forming. When encountering weak or broken stratum, it&#;s difficult to drill hole and even happen collapse, while self drilling anchor bar avoids these shortcomings. After drilling hole, anchor bar is stayed in hole, which can not only avoid collapse, but also save time and reduce difficulty for construction.
3. Strong adaptability. Thread is spread on the whole body of self drilling anchor bar, it can be cut at any location and can be lengthened. It has different materials and sizes to suit for different construction conditions.
4. High anchorage strength. Thread on self drilling anchor bar has tight link with coupling and also with grouting body.
5. Good anchoring effect. When grouting, seriflux is grouted from bottom of hole, full and dense, so grouting quality is high.
6. Simple construction. Compared with common anchor bar, construction of self drilling anchor bar is simple and fast, it reduces working procedures of pull-out of hole, anchor bar installation and grouting pipe insert, etc.
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