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.
Self-drilling hollow anchor bolts within the extensive range of the Sinorock range of foundation and stability control products are moving beyond their traditional applications in underground construction and are being used also as micropiles. Vital to the protection of infrastructure above underground excavations, the expanded use of the SDA bolt provide efficient underpinning of the foundations of buildings and for stabilizing ground around excavations particularly in hard-to-reach sites with limited working space.
Sinorock hollow bar micropiles can be installed in every ground type and can withstand, reliably, both tension and compression loads of up to 2,750kN in tension and up to 1,910kN in compression. The hollow-bar design of the self-drilling hollow bar micropile system offers a single action for drilling and grouting. As an efficient method of stabilizing the subsoil, micropiling is becoming an ever more important method for preventing settlement of foundations for the long term.
Sinorock self drilling hollow anchor bar overcome these limitations and make the installation faster and more efficient with their one-step process. The bar is drilled into the ground and cement grout is injected through the hollow rod in one operation. During drilling, the grout stabilizes the borehole to prevent it collapsing. Once installed to the required length and after full hardening, the grout transfers the load from the bar into the surrounding soil. The simultaneous grouting ensures full and uniform coverage of grout along the full length of micropile. Extension couplings provides lengthening of the micropiles and the bearing capacity of the connection remains the same as of the bars.