Development of plasma bolt for rapid installation

Rock bolts are typically used for the ground reinforcement. Except some spot bolts, rock bolts are usually grouted with cement or resin grout. To use the bolts at seepage place or to improve installation speed, various type of friction bolts also have been developed. In this study, Plasma bolt, as an expandable rock bolt type, was developed which can be installed quickly and easily, and show immediate supporting effects by adopting the plasma technique. It is a hollow pipe drawn as round polygon shaped section with concavo-convex like a star shape filled with plasma trigger-parts and materials. Field installation and pull out tests were carried out. To optimize the design parameters of rock bolt, steel material, drawn section shape, cap type and composition of reactants and power factor were selected. The capacity of simultaneous multi installation of rock bolt was estimated according to the electrical condition of a high voltage electric device for generating plasma phenomena. Pull out load of optimized plasma bolt was more than 14 ton, which is sufficient for general tunnel support. Rock bolt installation was expected to be faster than existing bolts by the valuable advantage of simultaneous multi installation with dynamic expansion.