Construction control technology for cutting historical anchor cables along the path of shield tunnels crossing existing tunnels at close proximity

Abstract

In Dongguan Metro Line 1, the new shield tunnel crosses above the existing metro tunnel at a close proximity, necessitating strict control over the displacement of the existing tunnel caused by shield construction. In addition, on the left route of the new shield tunnel, anchor cables used to strengthen the stratum during the construction of the existing tunnel remain embedded in the soil. These anchor cables must be cut off to avoid damaging the shield machine. However, cutting these anchor cables may influence the stress states of the soil and existing tunnel, resulting in additional displacements. To address these challenges, an innovative cutting method for anchor cables was employed in this project. To strictly control the induced settlements of the existing tunnel during shield tunneling, the following measures were implemented: pregrouting reinforcement of the soil above the new tunnel, numerical simulation, and displacement monitoring. The construction of the new tunnel through shield tunneling was successfully completed. The monitoring data indicated minimal displacement of the existing tunnel, demonstrating effective construction control. The control technologies introduced in this study for constructing new shield tunnels crossing an existing tunnel serve as valuable reference for similar projects in the future.