Abstract
Soil nailing has been used to reinforce the unstable ground such as slope stability and face bolting in the bored tunnels. In these civil engineering projects, the slender steel bars as reinforcement elements have been mainly used for axial tension load transfer. Alternatively, the usage of steel tubular pipes is highlighted for constructability reasons and an extra bend/shear resistance of pipes. However, commercially available steel pipes have smooth surface so that the bond strength is not enough to resist the pull-out tension loads. Therefore, the fabrication such as shear keys on the outer surface of the pipe is essential to obtain the bond strength between the pipe and the grout filling. The dimpled pipes using on-line depression forming method has been developed to improve the bond strength, which has small depressions regularly arranged on the outer surface. This paper presents the introduction of the dimpled pipe briefly, and a particular emphasis is given to the evaluation of the high bond strength by the pull-out tests and the mechanism.
