Abstract: To address challenges related to untimely gravel backfilling, suboptimal backfilling effects, and delayed grouting behind the doubleshield tunnel boring machine(TBM) segment, a novel TBM shield tail sealing plate that is characterized by high wearresistance, easy assembly, elevated elasticity, and effective sealing is proposed. This design considers the structural mode of the TBM shield tail and its positional relationship with surrounding rocks and segments, facilitating synchronous backfilling of gravel and bottom grouting. To validate the feasibility of this technology, a field test is conducted on a section of Qingdao metro line 6. Primary indices, such as grout mixing ratio, grouting amount, and positions are collected. The results highlight the following key findings: (1) The installation of the sealing plate ensures the advance backfilling of gravel, thereby creating favorable conditions for synchronous bottom grouting. (2) A slurry with a watercement ratio of 2.3∶5 and a consistency of less than 13 cm is sufficient to meet the gravel grouting requirements. (3) For the lower segment, it is recommended that grouting points be positioned at a 60° angle against the 〖WT〗Y〖WT５《TNR》〗line of the tunnel crosssection to prevent grout overflow.

Key words: metro, doubleshield tunnel boring machine, segment, gravel, grouting, synchronous backfill