The underground is often used during construction of infrastructure works such as railroads, metro, and roads. Tunnelling is however costly and stipulates high demand on safety and environmental consciousness. With regards to the environment the tunnels need to be sealed to reduce seepage of water into the tunnel and to avoid harmful lowering of the ground water table and potential damages to the surroundings. Sealing of the tunnels are usually performed with grouting, and to increase the possibility to achieve good results many research projects have been performed. What has not been studied to any great extent previously is the largescale variation of hydrogeological properties or the importance of the contractors works and process limitations. In this project several field studies have been used with the objective to study the grouting process. In every case study hundreds or thousands of grout holes have been analysed. The case studies show that there is a correlation between seepage of water, grout take and most prominently the existence of zones. This means that there is a possibility to identify more conductive areas with for example grout take and consequently to increase the amount of grout works in these areas to reduce the seepage into the tunnel. This project has also studied the grout theory and the application of ”The real-time grout control method” and shows that the theory is applicable to interpret the grout process and may also be useful to identify effects on the fractures/rock mass such as for example jacking.