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.
In this work the hydraulic conductivity of the rock mass has been studied and concluded that the hydraulic conductivity is a lognormal distribution. It is also shown that the measurements are depending on scale where the geometric mean are depending on the measured interval length. The REV, representative elementary volume, is discussed and it is shown that for the presented data the rock volume needs to be about km sized for the variations in measurements to be negligible. This also means that for a larger scale, the hydraulic conductivity will go towards the arithmetic mean. This also means that many measurements that is performed in 3 m lengths is not representative and needs to be scaled up to at least grout hole scale to be able to describe both the hydraulic conductivity and the grout result as well as an alternative method to analyse seepage
The report is based on a licentiate thesis from Chalmers and the work has mainly been performed by Björn Stille (Chalmers), with advise and support from Gunnar Gustafson (Chalmers), Håkan Stille (KTH) and Shinji Kobayashi (KTH and Shimizu Corp.). Supervisor was Lars O Ericsson (Chalmers).
The project has been financed by Skanska, SBUF and BeFo.
Stockholm
Patrik Vidstrand
