Abstract: Synchronous grouting is usually adopted to control the ground settlement during the shielded tunnel excavations. Based on the project of Metro Line No.12 beneath the Line 10 in Beijing, this paper investigates the deformation control of a tunnel excavation close to an existing tunnel. Based on the consolidation deformation characteristics of the synchronous grouting material, a method for predicting the deformation induced by the gap at the end of shielding under the synchronous grouting is proposed. The numerical simulation was used to analyze the deformation of the existing tunnel. The results indicate that, the maximum settlement of existing tunnel was -4.08 mm, which was greater than the control value. The measured deformation suggested that the synchronous grouting alone could not guarantee the safe operation of the existing tunnel. Upon deformation prediction, methods of onsite soil reinforcement and isolation zones were adopted to reduce deformation of existing tunnels.

Key words: Shielded Tunnel Undercrossing, Synchronous Grouting, Gap at the End of Shielding, Deformation Control