The hollow bar anchor technique has been used in the United States as a self-grouting soil nails which replaces the traditional drill and grout method. The drilling, installation and grouting of nailing in this method is combined into one single step. This method proves to be advantageous for caving ground conditions and was initially employed for temporary shoring applications.
The accessories for hollow core bar soil nails include washers, nuts, bearing plates, couplers and centralizers.The drill rig used on soil nailing projects using hollow core bars has the capacity to adapt to various sizes of hollow core bars and drill bits. Hydraulic rotary or rotary percussion drill rigs are commonly used. The rigs can be tack mounted or excavator mounted .The versatility of drilling rigs and concurrent drilling, installing and grouting procedure of hollow soil nails have worked well for remote access.
During tunnel construction, hollow and loose massive accumulation body often appears at portal section. The stability of rock is poor and local region is easy to happen collapse, so pipe shed is adopted to support in advance.
Because of poor rock stability, it’s difficult for drilling machine to form hole. While regular pipe shed is often steel tube with eyelet on its surface, jacking and grouting methods are needed when construction, so it’s difficult to install. Self drilling hollow anchor bar can solve this problem effectively.
Self drilling hollow anchor bar with drill bit can drill hole with common drilling machine. When reaching to designed location, self drilling anchor and drill bit are left in rock body, grouting can be proceeded directly. Unlike pipe shed, self drilling hollow anchor has injected holes on the top of drill bit, slurry is from bottom to eyelet, then diffuses all around to reinforce surrounding rock. Without pulling out hollow anchor bar and drill bit, it has strong adaptation on surrounding rock, even drilling and grouting at loose and broken surrounding rock.