Quality Assessment of Grout Performance in Alluvial Deposits by Means of Water-Pressure Test Along with Core Recovery Analysis with Reference to Section S2-X2 Line 2 Tehran Subway Tunnel

Line 2 Tehran Subway Tunnel has been excavated by a special designed TBM with an open face shield. Then the prefabricated reinforced segmental concrete lining, type (8+1), has been erected as a permanent support system. Subsequently, cementitious grout was used to create a peripheral water sealing curtain to prevent inrush water into the tunnel. In this paper, the effort has been made to deeply investigate the principles and technology employed in grouting of and improving the alluvial deposits surrounding Line 2 Tehran Subway Tunnel. Hence, the results obtained from laboratory tests along with in-situ water pressure tests (WPT) were used to evaluate the influence of grouts on strength characteristic of the in-situ alluvial deposits. The results revealed considerable changes due to cementitious grouts in decreasing permeability and displacement, and the increase in strength characteristics of the surrounding alluvial deposits as well. Furthermore, for the first time, also in this paper, the grouted soil samples were used to analyze the grout distribution within the samples visually. The results were also used to establish an empirical relation within the parameters involved. Hence, an empirical equation has been proposed by which the percentage of quality of grouted soils can be estimated.