Abstract When the slurry shield machine is used for excavation in the silty-fine sand layer, it is easy to cause problems such as the collapse of tunnel face, difficulty in cutterhead releasing, and difficulty in recovery of advance.Taking the construction of the Heyan Road River Crossing Tunnel in Nanjing as an example, by analyzing the collapse process of tunnel face in the silty-fine sand layer, specifically focusing on such aspects as the control of slurry chamber pressure, slurry performance adjustment, and tunnelling parameter control, the cutterhead releasing method for the extra-large diameter shield machine is studied and the engineering experience of effectively controlling the risk of tunnel face collapse and quickly restoring to the normal working condition is summarized. At the same time, based on the principle of bubble chamber pressure balance and the changes in tunnelling parameters, the following conclusions are drawn: (1) Before the collapse of tunnel face in the silty-fine sand layer, the tunnelling parameters of the slurry shield machine vary most significantly in the discharged slurry density and water pressure at cutting face. Multiple abnormal increases in the discharged slurry density and unstable water pressure at cutting face can serve as accident signs. (2) After the collapse of the tunnel face, the principle of "low rotation speed, large penetration and many times of short-time stops" should be followed to resume tunnelling.
Abstract：
When the slurry shield machine is used for excavation in the silty-fine sand layer, it is easy to cause problems such as the collapse of tunnel face, difficulty in cutterhead releasing, and difficulty in recovery of advance.Taking the construction of the Heyan Road River Crossing Tunnel in Nanjing as an example, by analyzing the collapse process of tunnel face in the silty-fine sand layer, specifically focusing on such aspects as the control of slurry chamber pressure, slurry performance adjustment, and tunnelling parameter control, the cutterhead releasing method for the extra-large diameter shield machine is studied and the engineering experience of effectively controlling the risk of tunnel face collapse and quickly restoring to the normal working condition is summarized. At the same time, based on the principle of bubble chamber pressure balance and the changes in tunnelling parameters, the following conclusions are drawn: (1) Before the collapse of tunnel face in the silty-fine sand layer, the tunnelling parameters of the slurry shield machine vary most significantly in the discharged slurry density and water pressure at cutting face. Multiple abnormal increases in the discharged slurry density and unstable water pressure at cutting face can serve as accident signs. (2) After the collapse of the tunnel face, the principle of "low rotation speed, large penetration and many times of short-time stops" should be followed to resume tunnelling.
LI Zifeng1 DUAN Baoliang2
.Study on Tunnel Face Collapse and Corresponding Treatment Measures in Shield Tunnelling in Silty-fine Sand Layer[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(4): 237-245
2023, Vol. 60 