Hollow bar micropiles are becoming a popular option for foundation retrofitting because of their fast installation and effectiveness as both a foundation system and ground improvement at the same time.
Self drilling hollow grouting bolt is made up of drill bit，hollow rod body,anchor plate and anchor nut.It is mainly used for the supporting engineering in the loose and broken rock strata with difficult to drilling hole.Different is available to cater for the different rock strata condition.
A variety of types and diameters of sacrificial cutting head / drill bits are available for installation in varying subsurface conditions. The grout to ground bond stress is directly proportional to the drill bit diameter, so proper bit selection is critical both for installation and for optimizing hollow bar micropile capacity.
The Sinorock hollow-bar micropile is a composite monolithic structure of micro alloy steel and high-strength cement grout. The hollow steel bar has a continuous external thread running the entire length of the bar and is advanced under rotation and possibly with some hammering action in very stiff or hard soils. As the bar is advanced,the grout is injected through the hollow bar and out through the sacrificial cutting head.
Since the outside diameter of the cutting head is typically 1 to 4 times larger than the outside diameter of the bar, the grout (under pressure) will flush the drill cuttings to the surface through the cavity along the outside of the bar and the wall of the excavation created by the cutting head.