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  Comparison between simultaneous backfilling methods with two components and single component grouts in EPB shield tunneling

  According to the dimensional difference between the excavation diameter and the outer diameter of lining, a space called “Annular gap” remains between them after excavation and advancement. Therefore one of the vital and integral parts of advancing mechanized tunneling especially in urban areas is to how to fill this space using grout filler. Usually, two components and single component grouting methods are being used in order to fill the annular gap. The main objectives of injection behind the segments are as follows: Decreasing the ground surface settlement above the tunnel. In the case that the annular gap is not completely filled after the passing of the shield, the ground motion and ground loss into this space will cause the ground surface settlement. Completely filing of annular gap and in turn creating a uniform contact area between the tunnel lining and ground, prevent from exertion of the point pressures on the segment body. Fixation and holding of the segment ring in its place after passing the shield. Bearing the loads imposed by the support system and transportation system on the invert segment. Completion of tunnel sealing. Inhibition of ring distortions. In this study, first, two components and Single Component Grout methods are separately described. For each of these two methods, control parameters, standards, acceptance levels and mix design used in various projects have been offered; then, by comparing these two methods, the advantages and disadvantages of them are presented. Finally the results are summarized and presented for the optimal choice of each of these methods according to the type and conditions of the project.

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