State-of-the-art microcement pre-injection for the Jong–Asker Rail Tunnel, Norway

Pre-injection of rock in underground construction involves pressure grouting into the rock mass through drill holes. The actual injection is part of a cycle that comprises exploratory drilling (probe drilling), injection drilling, injection, and control drilling. The holes are mostly drilled with modern, conventional drilling equipment e.g. a drill jumbo, with drill hole diameters of 45 to 64 mm, similar to those shown in Figure 1.