As a new construction technology, self drilling anchor system has been widely applied in hydroelectric station. It overcomes technical difficulties in loose rock conditions, realizes the primary stabilization by combining jetting cement and drainage hole method.
Self drilling anchor bolt is the main operating unit in self drilling anchor system. It is hollow and has full thread on surface. Coupling is adopted to lengthen it and one-off drill bit is installed on the front end.
Because of special structures, self drilling anchor bolt has following advantages:
1. High efficiency: self drilling anchor bolt combines drilling, grouting and anchoring together, which can be done at the same time, time-saving and high-efficient. Compared with common anchor bolt, it decreases the processes of pulling out of hole, installing anchor bar and inserting grouting pipes, which is quick and simple.
2. High adaptability: It is suitable for stratum which is difficult to drill hole, such as loose and broken surrounding rocks. After drilling holes, anchor bar stays in the hole, which avoids collapse, saves time and reduces construction difficulties. With whole thread on surface, it can be cut at any position. So it is suitable for different construction conditions.
3. High anchoring force and good anchoring effect: The thread of self drilling anchor bolt is generally R-thread or T-thread. They connect with coupling tightly and have good bonding effect with grouting slurry. When grouting, slurry is from the bottom to orifice, full and dense. Grouting quality is good.
Besides, self drilling anchor bolt in high slope of hydroelectric station has other features, such as big tensile pulling force of single anchor bolt, great depth, control or reduction occurrence of rock burst, enhance ability of anti-seismic and control deformation effectively.