Grouting applications in the Istanbul metro, Turkey

The first stage of the Istanbul metro construction was conducted in sandstone and mudstones of Carboniferous age. On the basis of Lugeon tests, the rock mass permeability was found to be in the range of 10−5–10−7. Since, no waterproofing system was placed in between the primary support and the final lining to maintain the imperviousness during operation of the subway, the cracking of the concrete lining and water inflow problems, such as leakage through the repair, dripping and surface moisture caused difficulties for the operation of the metro system. In order to overcome these problems, three different contact grouting methods, repair grouting and chemical grouting works were carried out. Regarding homogeneity of the grout take, labor and time-dependency of the equipment, the most successful results were obtained from one of the contact grouting types and repair grouting. Chemical grouting works yielded unsatisfactory results. Moreover, alteration, fracture spacing, groundwater and excess excavation properties of the rock mass were investigated in comparison with the contact grout take. The comparison between these properties and the grout take indicates no close relationship, and the grout take values are found to be affected mainly by the labor of grouting and excavation.In addition, in order to improve the rock mass along the metro route, consolidation grouting works were conducted. However, grouting works with the use of Portland cement conducted in the rock mass of very low permeability do not yield successful results.