Grouting Design Considering Different Geological Conditions : Grout evaluation for the extension of the Blue Metro Line

Abstract: This thesis forms the basis for a new documented experience of grouting design and work in the extension of the blue metro line in Stockholm. It includes documentation of the grouting design based on theoretical basis, stop criteria and fan geometries for favorable and unfavorable geological conditions. The work is concerned in evaluating the design stop criteria in different geological conditions to assess the efficiency of grouting process, and its compatibility to the maximum permissible leakage according to applications submitted to the land and environmental court in Stockholm. The work was conducted in cooperation with TYPSA AB and SWECO; the joint venture who designed the grouting work. This work was initiated by studying the design documents and reports, requirements, geological and hydrogeological prognosis documents. Six access tunnels were analyzed, with different work percentage based on the actual work achieved at the site at the time of conducting the study. Each access tunnel stretch was determined in terms of geological condition (rock quality), hydrogeological domain, and grouting class (IK1, IK2 or IK3). Evaluations and assessments were done for different aspects including evaluating the grout volume uptake per each grouting class, calculating the percentage of boreholes that stopped by time, volume or zero flow per grouting class, and comparing the measured leakage with prognosed leakage to check the efficiency of the design and implementation phases. RTGC (Real Time Grouting Control) method was also applied on some fans to check its validity in grout optimization, knowing that it is a relatively new method and not yet fully validated. The results showed that geological mappings during the implementation phase were slightly different from the mappings done during the design phase, which is expected due to the high uncertainties in rock mass science. It was also shown that the design stop criteria in this project were promising, through which they have satisfied the requirements according to the application to the land and environmental court. Average grout uptake in typical injection classes were compatible with the results in City Line projects, where the average grout uptake in 2 L/m. However, results also showed that in weakness zones, the average grout uptake was different with high standard deviations. Knowing the fact that unfavorable geological conditions were classified based on different parameters, it is not possible to find one reference value for the grout uptake, but instead results can be used as references in similar geological conditions in main tunnels work and future projects. Some recommendations are made in this thesis on the design stop criteria in weakness zones, surface rock domains, and at fans injected at large water depth. These zones always form the basis for controversial discussions and thus, if documentation of grouting work is carried out and continued in this project, then more knowledge can be gained and transferred to other projects. As part of this thesis, RTGC was applied in favorable conditions where it showed very promising results, the matter that makes it possible to optimize the stop criteria and actual work by conducting trial grouting. However, in unfavorable geological conditions, the RTGC could not be applied because the dimensionality of the flow is 3D, while RTGC was developed for 1D and 1D flow. Therefore, and since it was proven to be as a promising tool, further studies are recommended to develop the method for 3D flow.